/*-------------------------------------------------------------------------
*
* reorderbuffer.c
* PostgreSQL logical replay/reorder buffer management
*
*
* Copyright (c) 2012-2019, PostgreSQL Global Development Group
*
*
* IDENTIFICATION
* src/backend/replication/reorderbuffer.c
*
* NOTES
* This module gets handed individual pieces of transactions in the order
* they are written to the WAL and is responsible to reassemble them into
* toplevel transaction sized pieces. When a transaction is completely
* reassembled - signalled by reading the transaction commit record - it
* will then call the output plugin (cf. ReorderBufferCommit()) with the
* individual changes. The output plugins rely on snapshots built by
* snapbuild.c which hands them to us.
*
* Transactions and subtransactions/savepoints in postgres are not
* immediately linked to each other from outside the performing
* backend. Only at commit/abort (or special xact_assignment records) they
* are linked together. Which means that we will have to splice together a
* toplevel transaction from its subtransactions. To do that efficiently we
* build a binary heap indexed by the smallest current lsn of the individual
* subtransactions' changestreams. As the individual streams are inherently
* ordered by LSN - since that is where we build them from - the transaction
* can easily be reassembled by always using the subtransaction with the
* smallest current LSN from the heap.
*
* In order to cope with large transactions - which can be several times as
* big as the available memory - this module supports spooling the contents
* of a large transactions to disk. When the transaction is replayed the
* contents of individual (sub-)transactions will be read from disk in
* chunks.
*
* This module also has to deal with reassembling toast records from the
* individual chunks stored in WAL. When a new (or initial) version of a
* tuple is stored in WAL it will always be preceded by the toast chunks
* emitted for the columns stored out of line. Within a single toplevel
* transaction there will be no other data carrying records between a row's
* toast chunks and the row data itself. See ReorderBufferToast* for
* details.
*
* ReorderBuffer uses two special memory context types - SlabContext for
* allocations of fixed-length structures (changes and transactions), and
* GenerationContext for the variable-length transaction data (allocated
* and freed in groups with similar lifespan).
*
* -------------------------------------------------------------------------
*/
#include "postgres.h"
#include <unistd.h>
#include <sys/stat.h>
#include "access/heapam.h"
#include "access/rewriteheap.h"
#include "access/transam.h"
#include "access/tuptoaster.h"
#include "access/xact.h"
#include "access/xlog_internal.h"
#include "catalog/catalog.h"
#include "lib/binaryheap.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "replication/logical.h"
#include "replication/reorderbuffer.h"
#include "replication/slot.h"
#include "replication/snapbuild.h" /* just for SnapBuildSnapDecRefcount */
#include "storage/bufmgr.h"
#include "storage/fd.h"
#include "storage/sinval.h"
#include "utils/builtins.h"
#include "utils/combocid.h"
#include "utils/memdebug.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/relfilenodemap.h"
/* entry for a hash table we use to map from xid to our transaction state */
typedef struct ReorderBufferTXNByIdEnt
{
TransactionId xid;
ReorderBufferTXN *txn;
} ReorderBufferTXNByIdEnt;
/* data structures for (relfilenode, ctid) => (cmin, cmax) mapping */
typedef struct ReorderBufferTupleCidKey
{
RelFileNode relnode;
ItemPointerData tid;
} ReorderBufferTupleCidKey;
typedef struct ReorderBufferTupleCidEnt
{
ReorderBufferTupleCidKey key;
CommandId cmin;
CommandId cmax;
CommandId combocid; /* just for debugging */
} ReorderBufferTupleCidEnt;
/* k-way in-order change iteration support structures */
typedef struct ReorderBufferIterTXNEntry
{
XLogRecPtr lsn;
ReorderBufferChange *change;
ReorderBufferTXN *txn;
int fd;
XLogSegNo segno;
} ReorderBufferIterTXNEntry;
typedef struct ReorderBufferIterTXNState
{
binaryheap *heap;
Size nr_txns;
dlist_head old_change;
ReorderBufferIterTXNEntry entries[FLEXIBLE_ARRAY_MEMBER];
} ReorderBufferIterTXNState;
/* toast datastructures */
typedef struct ReorderBufferToastEnt
{
Oid chunk_id; /* toast_table.chunk_id */
int32 last_chunk_seq; /* toast_table.chunk_seq of the last chunk we
* have seen */
Size num_chunks; /* number of chunks we've already seen */
Size size; /* combined size of chunks seen */
dlist_head chunks; /* linked list of chunks */
struct varlena *reconstructed; /* reconstructed varlena now pointed to in
* main tup */
} ReorderBufferToastEnt;
/* Disk serialization support datastructures */
typedef struct ReorderBufferDiskChange
{
Size size;
ReorderBufferChange change;
/* data follows */
} ReorderBufferDiskChange;
/*
* Maximum number of changes kept in memory, per transaction. After that,
* changes are spooled to disk.
*
* The current value should be sufficient to decode the entire transaction
* without hitting disk in OLTP workloads, while starting to spool to disk in
* other workloads reasonably fast.
*
* At some point in the future it probably makes sense to have a more elaborate
* resource management here, but it's not entirely clear what that would look
* like.
*/
static const Size max_changes_in_memory = 4096;
/* ---------------------------------------
* primary reorderbuffer support routines
* ---------------------------------------
*/
static ReorderBufferTXN *ReorderBufferGetTXN(ReorderBuffer *rb);
static void ReorderBufferReturnTXN(ReorderBuffer *rb, ReorderBufferTXN *txn);
static ReorderBufferTXN *ReorderBufferTXNByXid(ReorderBuffer *rb,
TransactionId xid, bool create, bool *is_new,
XLogRecPtr lsn, bool create_as_top);
static void ReorderBufferTransferSnapToParent(ReorderBufferTXN *txn,
ReorderBufferTXN *subtxn);
static void AssertTXNLsnOrder(ReorderBuffer *rb);
/* ---------------------------------------
* support functions for lsn-order iterating over the ->changes of a
* transaction and its subtransactions
*
* used for iteration over the k-way heap merge of a transaction and its
* subtransactions
* ---------------------------------------
*/
static ReorderBufferIterTXNState *ReorderBufferIterTXNInit(ReorderBuffer *rb, ReorderBufferTXN *txn);
static ReorderBufferChange *ReorderBufferIterTXNNext(ReorderBuffer *rb, ReorderBufferIterTXNState *state);
static void ReorderBufferIterTXNFinish(ReorderBuffer *rb,
ReorderBufferIterTXNState *state);
static void ReorderBufferExecuteInvalidations(ReorderBuffer *rb, ReorderBufferTXN *txn);
/*
* ---------------------------------------
* Disk serialization support functions
* ---------------------------------------
*/
static void ReorderBufferCheckSerializeTXN(ReorderBuffer *rb, ReorderBufferTXN *txn);
static void ReorderBufferSerializeTXN(ReorderBuffer *rb, ReorderBufferTXN *txn);
static void ReorderBufferSerializeChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
int fd, ReorderBufferChange *change);
static Size ReorderBufferRestoreChanges(ReorderBuffer *rb, ReorderBufferTXN *txn,
int *fd, XLogSegNo *segno);
static void ReorderBufferRestoreChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
char *change);
static void ReorderBufferRestoreCleanup(ReorderBuffer *rb, ReorderBufferTXN *txn);
static void ReorderBufferCleanupSerializedTXNs(const char *slotname);
static void ReorderBufferSerializedPath(char *path, ReplicationSlot *slot,
TransactionId xid, XLogSegNo segno);
static void ReorderBufferFreeSnap(ReorderBuffer *rb, Snapshot snap);
static Snapshot ReorderBufferCopySnap(ReorderBuffer *rb, Snapshot orig_snap,
ReorderBufferTXN *txn, CommandId cid);
/* ---------------------------------------
* toast reassembly support
* ---------------------------------------
*/
static void ReorderBufferToastInitHash(ReorderBuffer *rb, ReorderBufferTXN *txn);
static void ReorderBufferToastReset(ReorderBuffer *rb, ReorderBufferTXN *txn);
static void ReorderBufferToastReplace(ReorderBuffer *rb, ReorderBufferTXN *txn,
Relation relation, ReorderBufferChange *change);
static void ReorderBufferToastAppendChunk(ReorderBuffer *rb, ReorderBufferTXN *txn,
Relation relation, ReorderBufferChange *change);
/*
* Allocate a new ReorderBuffer and clean out any old serialized state from
* prior ReorderBuffer instances for the same slot.
*/
ReorderBuffer *
ReorderBufferAllocate(void)
{
ReorderBuffer *buffer;
HASHCTL hash_ctl;
MemoryContext new_ctx;
Assert(MyReplicationSlot != NULL);
/* allocate memory in own context, to have better accountability */
new_ctx = AllocSetContextCreate(CurrentMemoryContext,
"ReorderBuffer",
ALLOCSET_DEFAULT_SIZES);
buffer =
(ReorderBuffer *) MemoryContextAlloc(new_ctx, sizeof(ReorderBuffer));
memset(&hash_ctl, 0, sizeof(hash_ctl));
buffer->context = new_ctx;
buffer->change_context = SlabContextCreate(new_ctx,
"Change",
SLAB_DEFAULT_BLOCK_SIZE,
sizeof(ReorderBufferChange));
buffer->txn_context = SlabContextCreate(new_ctx,
"TXN",
SLAB_DEFAULT_BLOCK_SIZE,
sizeof(ReorderBufferTXN));
buffer->tup_context = GenerationContextCreate(new_ctx,
"Tuples",
SLAB_LARGE_BLOCK_SIZE);
hash_ctl.keysize = sizeof(TransactionId);
hash_ctl.entrysize = sizeof(ReorderBufferTXNByIdEnt);
hash_ctl.hcxt = buffer->context;
buffer->by_txn = hash_create("ReorderBufferByXid", 1000, &hash_ctl,
HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
buffer->by_txn_last_xid = InvalidTransactionId;
buffer->by_txn_last_txn = NULL;
buffer->outbuf = NULL;
buffer->outbufsize = 0;
buffer->current_restart_decoding_lsn = InvalidXLogRecPtr;
dlist_init(&buffer->toplevel_by_lsn);
dlist_init(&buffer->txns_by_base_snapshot_lsn);
/*
* Ensure there's no stale data from prior uses of this slot, in case some
* prior exit avoided calling ReorderBufferFree. Failure to do this can
* produce duplicated txns, and it's very cheap if there's nothing there.
*/
ReorderBufferCleanupSerializedTXNs(NameStr(MyReplicationSlot->data.name));
return buffer;
}
/*
* Free a ReorderBuffer
*/
void
ReorderBufferFree(ReorderBuffer *rb)
{
MemoryContext context = rb->context;
/*
* We free separately allocated data by entirely scrapping reorderbuffer's
* memory context.
*/
MemoryContextDelete(context);
/* Free disk space used by unconsumed reorder buffers */
ReorderBufferCleanupSerializedTXNs(NameStr(MyReplicationSlot->data.name));
}
/*
* Get an unused, possibly preallocated, ReorderBufferTXN.
*/
static ReorderBufferTXN *
ReorderBufferGetTXN(ReorderBuffer *rb)
{
ReorderBufferTXN *txn;
txn = (ReorderBufferTXN *)
MemoryContextAlloc(rb->txn_context, sizeof(ReorderBufferTXN));
memset(txn, 0, sizeof(ReorderBufferTXN));
dlist_init(&txn->changes);
dlist_init(&txn->tuplecids);
dlist_init(&txn->subtxns);
return txn;
}
/*
* Free a ReorderBufferTXN.
*/
static void
ReorderBufferReturnTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
{
/* clean the lookup cache if we were cached (quite likely) */
if (rb->by_txn_last_xid == txn->xid)
{
rb->by_txn_last_xid = InvalidTransactionId;
rb->by_txn_last_txn = NULL;
}
/* free data that's contained */
if (txn->tuplecid_hash != NULL)
{
hash_destroy(txn->tuplecid_hash);
txn->tuplecid_hash = NULL;
}
if (txn->invalidations)
{
pfree(txn->invalidations);
txn->invalidations = NULL;
}
pfree(txn);
}
/*
* Get an fresh ReorderBufferChange.
*/
ReorderBufferChange *
ReorderBufferGetChange(ReorderBuffer *rb)
{
ReorderBufferChange *change;
change = (ReorderBufferChange *)
MemoryContextAlloc(rb->change_context, sizeof(ReorderBufferChange));
memset(change, 0, sizeof(ReorderBufferChange));
return change;
}
/*
* Free an ReorderBufferChange.
*/
void
ReorderBufferReturnChange(ReorderBuffer *rb, ReorderBufferChange *change)
{
/* free contained data */
switch (change->action)
{
case REORDER_BUFFER_CHANGE_INSERT:
case REORDER_BUFFER_CHANGE_UPDATE:
case REORDER_BUFFER_CHANGE_DELETE:
case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT:
if (change->data.tp.newtuple)
{
ReorderBufferReturnTupleBuf(rb, change->data.tp.newtuple);
change->data.tp.newtuple = NULL;
}
if (change->data.tp.oldtuple)
{
ReorderBufferReturnTupleBuf(rb, change->data.tp.oldtuple);
change->data.tp.oldtuple = NULL;
}
break;
case REORDER_BUFFER_CHANGE_MESSAGE:
if (change->data.msg.prefix != NULL)
pfree(change->data.msg.prefix);
change->data.msg.prefix = NULL;
if (change->data.msg.message != NULL)
pfree(change->data.msg.message);
change->data.msg.message = NULL;
break;
case REORDER_BUFFER_CHANGE_INTERNAL_SNAPSHOT:
if (change->data.snapshot)
{
ReorderBufferFreeSnap(rb, change->data.snapshot);
change->data.snapshot = NULL;
}
break;
/* no data in addition to the struct itself */
case REORDER_BUFFER_CHANGE_TRUNCATE:
if (change->data.truncate.relids != NULL)
{
ReorderBufferReturnRelids(rb, change->data.truncate.relids);
change->data.truncate.relids = NULL;
}
break;
case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
break;
}
pfree(change);
}
/*
* Get a fresh ReorderBufferTupleBuf fitting at least a tuple of size
* tuple_len (excluding header overhead).
*/
ReorderBufferTupleBuf *
ReorderBufferGetTupleBuf(ReorderBuffer *rb, Size tuple_len)
{
ReorderBufferTupleBuf *tuple;
Size alloc_len;
alloc_len = tuple_len + SizeofHeapTupleHeader;
tuple = (ReorderBufferTupleBuf *)
MemoryContextAlloc(rb->tup_context,
sizeof(ReorderBufferTupleBuf) +
MAXIMUM_ALIGNOF + alloc_len);
tuple->alloc_tuple_size = alloc_len;
tuple->tuple.t_data = ReorderBufferTupleBufData(tuple);
return tuple;
}
/*
* Free an ReorderBufferTupleBuf.
*/
void
ReorderBufferReturnTupleBuf(ReorderBuffer *rb, ReorderBufferTupleBuf *tuple)
{
pfree(tuple);
}
/*
* Get an array for relids of truncated relations.
*
* We use the global memory context (for the whole reorder buffer), because
* none of the existing ones seems like a good match (some are SLAB, so we
* can't use those, and tup_context is meant for tuple data, not relids). We
* could add yet another context, but it seems like an overkill - TRUNCATE is
* not particularly common operation, so it does not seem worth it.
*/
Oid *
ReorderBufferGetRelids(ReorderBuffer *rb, int nrelids)
{
Oid *relids;
Size alloc_len;
alloc_len = sizeof(Oid) * nrelids;
relids = (Oid *) MemoryContextAlloc(rb->context, alloc_len);
return relids;
}
/*
* Free an array of relids.
*/
void
ReorderBufferReturnRelids(ReorderBuffer *rb, Oid *relids)
{
pfree(relids);
}
/*
* Return the ReorderBufferTXN from the given buffer, specified by Xid.
* If create is true, and a transaction doesn't already exist, create it
* (with the given LSN, and as top transaction if that's specified);
* when this happens, is_new is set to true.
*/
static ReorderBufferTXN *
ReorderBufferTXNByXid(ReorderBuffer *rb, TransactionId xid, bool create,
bool *is_new, XLogRecPtr lsn, bool create_as_top)
{
ReorderBufferTXN *txn;
ReorderBufferTXNByIdEnt *ent;
bool found;
Assert(TransactionIdIsValid(xid));
/*
* Check the one-entry lookup cache first
*/
if (TransactionIdIsValid(rb->by_txn_last_xid) &&
rb->by_txn_last_xid == xid)
{
txn = rb->by_txn_last_txn;
if (txn != NULL)
{
/* found it, and it's valid */
if (is_new)
*is_new = false;
return txn;
}
/*
* cached as non-existent, and asked not to create? Then nothing else
* to do.
*/
if (!create)
return NULL;
/* otherwise fall through to create it */
}
/*
* If the cache wasn't hit or it yielded an "does-not-exist" and we want
* to create an entry.
*/
/* search the lookup table */
ent = (ReorderBufferTXNByIdEnt *)
hash_search(rb->by_txn,
(void *) &xid,
create ? HASH_ENTER : HASH_FIND,
&found);
if (found)
txn = ent->txn;
else if (create)
{
/* initialize the new entry, if creation was requested */
Assert(ent != NULL);
Assert(lsn != InvalidXLogRecPtr);
ent->txn = ReorderBufferGetTXN(rb);
ent->txn->xid = xid;
txn = ent->txn;
txn->first_lsn = lsn;
txn->restart_decoding_lsn = rb->current_restart_decoding_lsn;
if (create_as_top)
{
dlist_push_tail(&rb->toplevel_by_lsn, &txn->node);
AssertTXNLsnOrder(rb);
}
}
else
txn = NULL; /* not found and not asked to create */
/* update cache */
rb->by_txn_last_xid = xid;
rb->by_txn_last_txn = txn;
if (is_new)
*is_new = !found;
Assert(!create || txn != NULL);
return txn;
}
/*
* Queue a change into a transaction so it can be replayed upon commit.
*/
void
ReorderBufferQueueChange(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn,
ReorderBufferChange *change)
{
ReorderBufferTXN *txn;
txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
change->lsn = lsn;
Assert(InvalidXLogRecPtr != lsn);
dlist_push_tail(&txn->changes, &change->node);
txn->nentries++;
txn->nentries_mem++;
ReorderBufferCheckSerializeTXN(rb, txn);
}
/*
* Queue message into a transaction so it can be processed upon commit.
*/
void
ReorderBufferQueueMessage(ReorderBuffer *rb, TransactionId xid,
Snapshot snapshot, XLogRecPtr lsn,
bool transactional, const char *prefix,
Size message_size, const char *message)
{
if (transactional)
{
MemoryContext oldcontext;
ReorderBufferChange *change;
Assert(xid != InvalidTransactionId);
oldcontext = MemoryContextSwitchTo(rb->context);
change = ReorderBufferGetChange(rb);
change->action = REORDER_BUFFER_CHANGE_MESSAGE;
change->data.msg.prefix = pstrdup(prefix);
change->data.msg.message_size = message_size;
change->data.msg.message = palloc(message_size);
memcpy(change->data.msg.message, message, message_size);
ReorderBufferQueueChange(rb, xid, lsn, change);
MemoryContextSwitchTo(oldcontext);
}
else
{
ReorderBufferTXN *txn = NULL;
volatile Snapshot snapshot_now = snapshot;
if (xid != InvalidTransactionId)
txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
/* setup snapshot to allow catalog access */
SetupHistoricSnapshot(snapshot_now, NULL);
PG_TRY();
{
rb->message(rb, txn, lsn, false, prefix, message_size, message);
TeardownHistoricSnapshot(false);
}
PG_CATCH();
{
TeardownHistoricSnapshot(true);
PG_RE_THROW();
}
PG_END_TRY();
}
}
/*
* AssertTXNLsnOrder
* Verify LSN ordering of transaction lists in the reorderbuffer
*
* Other LSN-related invariants are checked too.
*
* No-op if assertions are not in use.
*/
static void
AssertTXNLsnOrder(ReorderBuffer *rb)
{
#ifdef USE_ASSERT_CHECKING
dlist_iter iter;
XLogRecPtr prev_first_lsn = InvalidXLogRecPtr;
XLogRecPtr prev_base_snap_lsn = InvalidXLogRecPtr;
dlist_foreach(iter, &rb->toplevel_by_lsn)
{
ReorderBufferTXN *cur_txn = dlist_container(ReorderBufferTXN, node,
iter.cur);
/* start LSN must be set */
Assert(cur_txn->first_lsn != InvalidXLogRecPtr);
/* If there is an end LSN, it must be higher than start LSN */
if (cur_txn->end_lsn != InvalidXLogRecPtr)
Assert(cur_txn->first_lsn <= cur_txn->end_lsn);
/* Current initial LSN must be strictly higher than previous */
if (prev_first_lsn != InvalidXLogRecPtr)
Assert(prev_first_lsn < cur_txn->first_lsn);
/* known-as-subtxn txns must not be listed */
Assert(!cur_txn->is_known_as_subxact);
prev_first_lsn = cur_txn->first_lsn;
}
dlist_foreach(iter, &rb->txns_by_base_snapshot_lsn)
{
ReorderBufferTXN *cur_txn = dlist_container(ReorderBufferTXN,
base_snapshot_node,
iter.cur);
/* base snapshot (and its LSN) must be set */
Assert(cur_txn->base_snapshot != NULL);
Assert(cur_txn->base_snapshot_lsn != InvalidXLogRecPtr);
/* current LSN must be strictly higher than previous */
if (prev_base_snap_lsn != InvalidXLogRecPtr)
Assert(prev_base_snap_lsn < cur_txn->base_snapshot_lsn);
/* known-as-subtxn txns must not be listed */
Assert(!cur_txn->is_known_as_subxact);
prev_base_snap_lsn = cur_txn->base_snapshot_lsn;
}
#endif
}
/*
* ReorderBufferGetOldestTXN
* Return oldest transaction in reorderbuffer
*/
ReorderBufferTXN *
ReorderBufferGetOldestTXN(ReorderBuffer *rb)
{
ReorderBufferTXN *txn;
AssertTXNLsnOrder(rb);
if (dlist_is_empty(&rb->toplevel_by_lsn))
return NULL;
txn = dlist_head_element(ReorderBufferTXN, node, &rb->toplevel_by_lsn);
Assert(!txn->is_known_as_subxact);
Assert(txn->first_lsn != InvalidXLogRecPtr);
return txn;
}
/*
* ReorderBufferGetOldestXmin
* Return oldest Xmin in reorderbuffer
*
* Returns oldest possibly running Xid from the point of view of snapshots
* used in the transactions kept by reorderbuffer, or InvalidTransactionId if
* there are none.
*
* Since snapshots are assigned monotonically, this equals the Xmin of the
* base snapshot with minimal base_snapshot_lsn.
*/
TransactionId
ReorderBufferGetOldestXmin(ReorderBuffer *rb)
{
ReorderBufferTXN *txn;
AssertTXNLsnOrder(rb);
if (dlist_is_empty(&rb->txns_by_base_snapshot_lsn))
return InvalidTransactionId;
txn = dlist_head_element(ReorderBufferTXN, base_snapshot_node,
&rb->txns_by_base_snapshot_lsn);
return txn->base_snapshot->xmin;
}
void
ReorderBufferSetRestartPoint(ReorderBuffer *rb, XLogRecPtr ptr)
{
rb->current_restart_decoding_lsn = ptr;
}
/*
* ReorderBufferAssignChild
*
* Make note that we know that subxid is a subtransaction of xid, seen as of
* the given lsn.
*/
void
ReorderBufferAssignChild(ReorderBuffer *rb, TransactionId xid,
TransactionId subxid, XLogRecPtr lsn)
{
ReorderBufferTXN *txn;
ReorderBufferTXN *subtxn;
bool new_top;
bool new_sub;
txn = ReorderBufferTXNByXid(rb, xid, true, &new_top, lsn, true);
subtxn = ReorderBufferTXNByXid(rb, subxid, true, &new_sub, lsn, false);
if (new_top && !new_sub)
elog(ERROR, "subtransaction logged without previous top-level txn record");
if (!new_sub)
{
if (subtxn->is_known_as_subxact)
{
/* already associated, nothing to do */
return;
}
else
{
/*
* We already saw this transaction, but initially added it to the
* list of top-level txns. Now that we know it's not top-level,
* remove it from there.
*/
dlist_delete(&subtxn->node);
}
}
subtxn->is_known_as_subxact = true;
subtxn->toplevel_xid = xid;
Assert(subtxn->nsubtxns == 0);
/* add to subtransaction list */
dlist_push_tail(&txn->subtxns, &subtxn->node);
txn->nsubtxns++;
/* Possibly transfer the subtxn's snapshot to its top-level txn. */
ReorderBufferTransferSnapToParent(txn, subtxn);
/* Verify LSN-ordering invariant */
AssertTXNLsnOrder(rb);
}
/*
* ReorderBufferTransferSnapToParent
* Transfer base snapshot from subtxn to top-level txn, if needed
*
* This is done if the top-level txn doesn't have a base snapshot, or if the
* subtxn's base snapshot has an earlier LSN than the top-level txn's base
* snapshot's LSN. This can happen if there are no changes in the toplevel
* txn but there are some in the subtxn, or the first change in subtxn has
* earlier LSN than first change in the top-level txn and we learned about
* their kinship only now.
*
* The subtransaction's snapshot is cleared regardless of the transfer
* happening, since it's not needed anymore in either case.
*
* We do this as soon as we become aware of their kinship, to avoid queueing
* extra snapshots to txns known-as-subtxns -- only top-level txns will
* receive further snapshots.
*/
static void
ReorderBufferTransferSnapToParent(ReorderBufferTXN *txn,
ReorderBufferTXN *subtxn)
{
Assert(subtxn->toplevel_xid == txn->xid);
if (subtxn->base_snapshot != NULL)
{
if (txn->base_snapshot == NULL ||
subtxn->base_snapshot_lsn < txn->base_snapshot_lsn)
{
/*
* If the toplevel transaction already has a base snapshot but
* it's newer than the subxact's, purge it.
*/
if (txn->base_snapshot != NULL)
{
SnapBuildSnapDecRefcount(txn->base_snapshot);
dlist_delete(&txn->base_snapshot_node);
}
/*
* The snapshot is now the top transaction's; transfer it, and
* adjust the list position of the top transaction in the list by
* moving it to where the subtransaction is.
*/
txn->base_snapshot = subtxn->base_snapshot;
txn->base_snapshot_lsn = subtxn->base_snapshot_lsn;
dlist_insert_before(&subtxn->base_snapshot_node,
&txn->base_snapshot_node);
/*
* The subtransaction doesn't have a snapshot anymore (so it
* mustn't be in the list.)
*/
subtxn->base_snapshot = NULL;
subtxn->base_snapshot_lsn = InvalidXLogRecPtr;
dlist_delete(&subtxn->base_snapshot_node);
}
else
{
/* Base snap of toplevel is fine, so subxact's is not needed */
SnapBuildSnapDecRefcount(subtxn->base_snapshot);
dlist_delete(&subtxn->base_snapshot_node);
subtxn->base_snapshot = NULL;
subtxn->base_snapshot_lsn = InvalidXLogRecPtr;
}
}
}
/*
* Associate a subtransaction with its toplevel transaction at commit
* time. There may be no further changes added after this.
*/
void
ReorderBufferCommitChild(ReorderBuffer *rb, TransactionId xid,
TransactionId subxid, XLogRecPtr commit_lsn,
XLogRecPtr end_lsn)
{
ReorderBufferTXN *subtxn;
subtxn = ReorderBufferTXNByXid(rb, subxid, false, NULL,
InvalidXLogRecPtr, false);
/*
* No need to do anything if that subtxn didn't contain any changes
*/
if (!subtxn)
return;
subtxn->final_lsn = commit_lsn;
subtxn->end_lsn = end_lsn;
/*
* Assign this subxact as a child of the toplevel xact (no-op if already
* done.)
*/
ReorderBufferAssignChild(rb, xid, subxid, InvalidXLogRecPtr);
}
/*
* Support for efficiently iterating over a transaction's and its
* subtransactions' changes.
*
* We do by doing a k-way merge between transactions/subtransactions. For that
* we model the current heads of the different transactions as a binary heap
* so we easily know which (sub-)transaction has the change with the smallest
* lsn next.
*
* We assume the changes in individual transactions are already sorted by LSN.
*/
/*
* Binary heap comparison function.
*/
static int
ReorderBufferIterCompare(Datum a, Datum b, void *arg)
{
ReorderBufferIterTXNState *state = (ReorderBufferIterTXNState *) arg;
XLogRecPtr pos_a = state->entries[DatumGetInt32(a)].lsn;
XLogRecPtr pos_b = state->entries[DatumGetInt32(b)].lsn;
if (pos_a < pos_b)
return 1;
else if (pos_a == pos_b)
return 0;
return -1;
}
/*
* Allocate & initialize an iterator which iterates in lsn order over a
* transaction and all its subtransactions.
*/
static ReorderBufferIterTXNState *
ReorderBufferIterTXNInit(ReorderBuffer *rb, ReorderBufferTXN *txn)
{
Size nr_txns = 0;
ReorderBufferIterTXNState *state;
dlist_iter cur_txn_i;
int32 off;
/*
* Calculate the size of our heap: one element for every transaction that
* contains changes. (Besides the transactions already in the reorder
* buffer, we count the one we were directly passed.)
*/
if (txn->nentries > 0)
nr_txns++;
dlist_foreach(cur_txn_i, &txn->subtxns)
{
ReorderBufferTXN *cur_txn;
cur_txn = dlist_container(ReorderBufferTXN, node, cur_txn_i.cur);
if (cur_txn->nentries > 0)
nr_txns++;
}
/*
* TODO: Consider adding fastpath for the rather common nr_txns=1 case, no
* need to allocate/build a heap then.
*/
/* allocate iteration state */
state = (ReorderBufferIterTXNState *)
MemoryContextAllocZero(rb->context,
sizeof(ReorderBufferIterTXNState) +
sizeof(ReorderBufferIterTXNEntry) * nr_txns);
state->nr_txns = nr_txns;
dlist_init(&state->old_change);
for (off = 0; off < state->nr_txns; off++)
{
state->entries[off].fd = -1;
state->entries[off].segno = 0;
}
/* allocate heap */
state->heap = binaryheap_allocate(state->nr_txns,
ReorderBufferIterCompare,
state);
/*
* Now insert items into the binary heap, in an unordered fashion. (We
* will run a heap assembly step at the end; this is more efficient.)
*/
off = 0;
/* add toplevel transaction if it contains changes */
if (txn->nentries > 0)
{
ReorderBufferChange *cur_change;
if (txn->serialized)
{
/* serialize remaining changes */
ReorderBufferSerializeTXN(rb, txn);
ReorderBufferRestoreChanges(rb, txn, &state->entries[off].fd,
&state->entries[off].segno);
}
cur_change = dlist_head_element(ReorderBufferChange, node,
&txn->changes);
state->entries[off].lsn = cur_change->lsn;
state->entries[off].change = cur_change;
state->entries[off].txn = txn;
binaryheap_add_unordered(state->heap, Int32GetDatum(off++));
}
/* add subtransactions if they contain changes */
dlist_foreach(cur_txn_i, &txn->subtxns)
{
ReorderBufferTXN *cur_txn;
cur_txn = dlist_container(ReorderBufferTXN, node, cur_txn_i.cur);
if (cur_txn->nentries > 0)
{
ReorderBufferChange *cur_change;
if (cur_txn->serialized)
{
/* serialize remaining changes */
ReorderBufferSerializeTXN(rb, cur_txn);
ReorderBufferRestoreChanges(rb, cur_txn,
&state->entries[off].fd,
&state->entries[off].segno);
}
cur_change = dlist_head_element(ReorderBufferChange, node,
&cur_txn->changes);
state->entries[off].lsn = cur_change->lsn;
state->entries[off].change = cur_change;
state->entries[off].txn = cur_txn;
binaryheap_add_unordered(state->heap, Int32GetDatum(off++));
}
}
/* assemble a valid binary heap */
binaryheap_build(state->heap);
return state;
}
/*
* Return the next change when iterating over a transaction and its
* subtransactions.
*
* Returns NULL when no further changes exist.
*/
static ReorderBufferChange *
ReorderBufferIterTXNNext(ReorderBuffer *rb, ReorderBufferIterTXNState *state)
{
ReorderBufferChange *change;
ReorderBufferIterTXNEntry *entry;
int32 off;
/* nothing there anymore */
if (state->heap->bh_size == 0)
return NULL;
off = DatumGetInt32(binaryheap_first(state->heap));
entry = &state->entries[off];
/* free memory we might have "leaked" in the previous *Next call */
if (!dlist_is_empty(&state->old_change))
{
change = dlist_container(ReorderBufferChange, node,
dlist_pop_head_node(&state->old_change));
ReorderBufferReturnChange(rb, change);
Assert(dlist_is_empty(&state->old_change));
}
change = entry->change;
/*
* update heap with information about which transaction has the next
* relevant change in LSN order
*/
/* there are in-memory changes */
if (dlist_has_next(&entry->txn->changes, &entry->change->node))
{
dlist_node *next = dlist_next_node(&entry->txn->changes, &change->node);
ReorderBufferChange *next_change =
dlist_container(ReorderBufferChange, node, next);
/* txn stays the same */
state->entries[off].lsn = next_change->lsn;
state->entries[off].change = next_change;
binaryheap_replace_first(state->heap, Int32GetDatum(off));
return change;
}
/* try to load changes from disk */
if (entry->txn->nentries != entry->txn->nentries_mem)
{
/*
* Ugly: restoring changes will reuse *Change records, thus delete the
* current one from the per-tx list and only free in the next call.
*/
dlist_delete(&change->node);
dlist_push_tail(&state->old_change, &change->node);
if (ReorderBufferRestoreChanges(rb, entry->txn, &entry->fd,
&state->entries[off].segno))
{
/* successfully restored changes from disk */
ReorderBufferChange *next_change =
dlist_head_element(ReorderBufferChange, node,
&entry->txn->changes);
elog(DEBUG2, "restored %u/%u changes from disk",
(uint32) entry->txn->nentries_mem,
(uint32) entry->txn->nentries);
Assert(entry->txn->nentries_mem);
/* txn stays the same */
state->entries[off].lsn = next_change->lsn;
state->entries[off].change = next_change;
binaryheap_replace_first(state->heap, Int32GetDatum(off));
return change;
}
}
/* ok, no changes there anymore, remove */
binaryheap_remove_first(state->heap);
return change;
}
/*
* Deallocate the iterator
*/
static void
ReorderBufferIterTXNFinish(ReorderBuffer *rb,
ReorderBufferIterTXNState *state)
{
int32 off;
for (off = 0; off < state->nr_txns; off++)
{
if (state->entries[off].fd != -1)
CloseTransientFile(state->entries[off].fd);
}
/* free memory we might have "leaked" in the last *Next call */
if (!dlist_is_empty(&state->old_change))
{
ReorderBufferChange *change;
change = dlist_container(ReorderBufferChange, node,
dlist_pop_head_node(&state->old_change));
ReorderBufferReturnChange(rb, change);
Assert(dlist_is_empty(&state->old_change));
}
binaryheap_free(state->heap);
pfree(state);
}
/*
* Cleanup the contents of a transaction, usually after the transaction
* committed or aborted.
*/
static void
ReorderBufferCleanupTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
{
bool found;
dlist_mutable_iter iter;
/* cleanup subtransactions & their changes */
dlist_foreach_modify(iter, &txn->subtxns)
{
ReorderBufferTXN *subtxn;
subtxn = dlist_container(ReorderBufferTXN, node, iter.cur);
/*
* Subtransactions are always associated to the toplevel TXN, even if
* they originally were happening inside another subtxn, so we won't
* ever recurse more than one level deep here.
*/
Assert(subtxn->is_known_as_subxact);
Assert(subtxn->nsubtxns == 0);
ReorderBufferCleanupTXN(rb, subtxn);
}
/* cleanup changes in the toplevel txn */
dlist_foreach_modify(iter, &txn->changes)
{
ReorderBufferChange *change;
change = dlist_container(ReorderBufferChange, node, iter.cur);
ReorderBufferReturnChange(rb, change);
}
/*
* Cleanup the tuplecids we stored for decoding catalog snapshot access.
* They are always stored in the toplevel transaction.
*/
dlist_foreach_modify(iter, &txn->tuplecids)
{
ReorderBufferChange *change;
change = dlist_container(ReorderBufferChange, node, iter.cur);
Assert(change->action == REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID);
ReorderBufferReturnChange(rb, change);
}
/*
* Cleanup the base snapshot, if set.
*/
if (txn->base_snapshot != NULL)
{
SnapBuildSnapDecRefcount(txn->base_snapshot);
dlist_delete(&txn->base_snapshot_node);
}
/*
* Remove TXN from its containing list.
*
* Note: if txn->is_known_as_subxact, we are deleting the TXN from its
* parent's list of known subxacts; this leaves the parent's nsubxacts
* count too high, but we don't care. Otherwise, we are deleting the TXN
* from the LSN-ordered list of toplevel TXNs.
*/
dlist_delete(&txn->node);
/* now remove reference from buffer */
hash_search(rb->by_txn,
(void *) &txn->xid,
HASH_REMOVE,
&found);
Assert(found);
/* remove entries spilled to disk */
if (txn->serialized)
ReorderBufferRestoreCleanup(rb, txn);
/* deallocate */
ReorderBufferReturnTXN(rb, txn);
}
/*
* Build a hash with a (relfilenode, ctid) -> (cmin, cmax) mapping for use by
* HeapTupleSatisfiesHistoricMVCC.
*/
static void
ReorderBufferBuildTupleCidHash(ReorderBuffer *rb, ReorderBufferTXN *txn)
{
dlist_iter iter;
HASHCTL hash_ctl;
if (!txn->has_catalog_changes || dlist_is_empty(&txn->tuplecids))
return;
memset(&hash_ctl, 0, sizeof(hash_ctl));
hash_ctl.keysize = sizeof(ReorderBufferTupleCidKey);
hash_ctl.entrysize = sizeof(ReorderBufferTupleCidEnt);
hash_ctl.hcxt = rb->context;
/*
* create the hash with the exact number of to-be-stored tuplecids from
* the start
*/
txn->tuplecid_hash =
hash_create("ReorderBufferTupleCid", txn->ntuplecids, &hash_ctl,
HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
dlist_foreach(iter, &txn->tuplecids)
{
ReorderBufferTupleCidKey key;
ReorderBufferTupleCidEnt *ent;
bool found;
ReorderBufferChange *change;
change = dlist_container(ReorderBufferChange, node, iter.cur);
Assert(change->action == REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID);
/* be careful about padding */
memset(&key, 0, sizeof(ReorderBufferTupleCidKey));
key.relnode = change->data.tuplecid.node;
ItemPointerCopy(&change->data.tuplecid.tid,
&key.tid);
ent = (ReorderBufferTupleCidEnt *)
hash_search(txn->tuplecid_hash,
(void *) &key,
HASH_ENTER | HASH_FIND,
&found);
if (!found)
{
ent->cmin = change->data.tuplecid.cmin;
ent->cmax = change->data.tuplecid.cmax;
ent->combocid = change->data.tuplecid.combocid;
}
else
{
/*
* Maybe we already saw this tuple before in this transaction, but
* if so it must have the same cmin.
*/
Assert(ent->cmin == change->data.tuplecid.cmin);
/*
* cmax may be initially invalid, but once set it can only grow,
* and never become invalid again.
*/
Assert((ent->cmax == InvalidCommandId) ||
((change->data.tuplecid.cmax != InvalidCommandId) &&
(change->data.tuplecid.cmax > ent->cmax)));
ent->cmax = change->data.tuplecid.cmax;
}
}
}
/*
* Copy a provided snapshot so we can modify it privately. This is needed so
* that catalog modifying transactions can look into intermediate catalog
* states.
*/
static Snapshot
ReorderBufferCopySnap(ReorderBuffer *rb, Snapshot orig_snap,
ReorderBufferTXN *txn, CommandId cid)
{
Snapshot snap;
dlist_iter iter;
int i = 0;
Size size;
size = sizeof(SnapshotData) +
sizeof(TransactionId) * orig_snap->xcnt +
sizeof(TransactionId) * (txn->nsubtxns + 1);
snap = MemoryContextAllocZero(rb->context, size);
memcpy(snap, orig_snap, sizeof(SnapshotData));
snap->copied = true;
snap->active_count = 1; /* mark as active so nobody frees it */
snap->regd_count = 0;
snap->xip = (TransactionId *) (snap + 1);
memcpy(snap->xip, orig_snap->xip, sizeof(TransactionId) * snap->xcnt);
/*
* snap->subxip contains all txids that belong to our transaction which we
* need to check via cmin/cmax. That's why we store the toplevel
* transaction in there as well.
*/
snap->subxip = snap->xip + snap->xcnt;
snap->subxip[i++] = txn->xid;
/*
* subxcnt isn't decreased when subtransactions abort, so count manually.
* Since it's an upper boundary it is safe to use it for the allocation
* above.
*/
snap->subxcnt = 1;
dlist_foreach(iter, &txn->subtxns)
{
ReorderBufferTXN *sub_txn;
sub_txn = dlist_container(ReorderBufferTXN, node, iter.cur);
snap->subxip[i++] = sub_txn->xid;
snap->subxcnt++;
}
/* sort so we can bsearch() later */
qsort(snap->subxip, snap->subxcnt, sizeof(TransactionId), xidComparator);
/* store the specified current CommandId */
snap->curcid = cid;
return snap;
}
/*
* Free a previously ReorderBufferCopySnap'ed snapshot
*/
static void
ReorderBufferFreeSnap(ReorderBuffer *rb, Snapshot snap)
{
if (snap->copied)
pfree(snap);
else
SnapBuildSnapDecRefcount(snap);
}
/*
* Perform the replay of a transaction and its non-aborted subtransactions.
*
* Subtransactions previously have to be processed by
* ReorderBufferCommitChild(), even if previously assigned to the toplevel
* transaction with ReorderBufferAssignChild.
*
* We currently can only decode a transaction's contents when its commit
* record is read because that's the only place where we know about cache
* invalidations. Thus, once a toplevel commit is read, we iterate over the top
* and subtransactions (using a k-way merge) and replay the changes in lsn
* order.
*/
void
ReorderBufferCommit(ReorderBuffer *rb, TransactionId xid,
XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
TimestampTz commit_time,
RepOriginId origin_id, XLogRecPtr origin_lsn)
{
ReorderBufferTXN *txn;
volatile Snapshot snapshot_now;
volatile CommandId command_id = FirstCommandId;
bool using_subtxn;
ReorderBufferIterTXNState *volatile iterstate = NULL;
txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr,
false);
/* unknown transaction, nothing to replay */
if (txn == NULL)
return;
txn->final_lsn = commit_lsn;
txn->end_lsn = end_lsn;
txn->commit_time = commit_time;
txn->origin_id = origin_id;
txn->origin_lsn = origin_lsn;
/*
* If this transaction has no snapshot, it didn't make any changes to the
* database, so there's nothing to decode. Note that
* ReorderBufferCommitChild will have transferred any snapshots from
* subtransactions if there were any.
*/
if (txn->base_snapshot == NULL)
{
Assert(txn->ninvalidations == 0);
ReorderBufferCleanupTXN(rb, txn);
return;
}
snapshot_now = txn->base_snapshot;
/* build data to be able to lookup the CommandIds of catalog tuples */
ReorderBufferBuildTupleCidHash(rb, txn);
/* setup the initial snapshot */
SetupHistoricSnapshot(snapshot_now, txn->tuplecid_hash);
/*
* Decoding needs access to syscaches et al., which in turn use
* heavyweight locks and such. Thus we need to have enough state around to
* keep track of those. The easiest way is to simply use a transaction
* internally. That also allows us to easily enforce that nothing writes
* to the database by checking for xid assignments.
*
* When we're called via the SQL SRF there's already a transaction
* started, so start an explicit subtransaction there.
*/
using_subtxn = IsTransactionOrTransactionBlock();
PG_TRY();
{
ReorderBufferChange *change;
ReorderBufferChange *specinsert = NULL;
if (using_subtxn)
BeginInternalSubTransaction("replay");
else
StartTransactionCommand();
rb->begin(rb, txn);
iterstate = ReorderBufferIterTXNInit(rb, txn);
while ((change = ReorderBufferIterTXNNext(rb, iterstate)) != NULL)
{
Relation relation = NULL;
Oid reloid;
switch (change->action)
{
case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
/*
* Confirmation for speculative insertion arrived. Simply
* use as a normal record. It'll be cleaned up at the end
* of INSERT processing.
*/
if (specinsert == NULL)
elog(ERROR, "invalid ordering of speculative insertion changes");
Assert(specinsert->data.tp.oldtuple == NULL);
change = specinsert;
change->action = REORDER_BUFFER_CHANGE_INSERT;
/* intentionally fall through */
case REORDER_BUFFER_CHANGE_INSERT:
case REORDER_BUFFER_CHANGE_UPDATE:
case REORDER_BUFFER_CHANGE_DELETE:
Assert(snapshot_now);
reloid = RelidByRelfilenode(change->data.tp.relnode.spcNode,
change->data.tp.relnode.relNode);
/*
* Mapped catalog tuple without data, emitted while
* catalog table was in the process of being rewritten. We
* can fail to look up the relfilenode, because the
* relmapper has no "historic" view, in contrast to normal
* the normal catalog during decoding. Thus repeated
* rewrites can cause a lookup failure. That's OK because
* we do not decode catalog changes anyway. Normally such
* tuples would be skipped over below, but we can't
* identify whether the table should be logically logged
* without mapping the relfilenode to the oid.
*/
if (reloid == InvalidOid &&
change->data.tp.newtuple == NULL &&
change->data.tp.oldtuple == NULL)
goto change_done;
else if (reloid == InvalidOid)
elog(ERROR, "could not map filenode \"%s\" to relation OID",
relpathperm(change->data.tp.relnode,
MAIN_FORKNUM));
relation = RelationIdGetRelation(reloid);
if (relation == NULL)
elog(ERROR, "could not open relation with OID %u (for filenode \"%s\")",
reloid,
relpathperm(change->data.tp.relnode,
MAIN_FORKNUM));
if (!RelationIsLogicallyLogged(relation))
goto change_done;
/*
* Ignore temporary heaps created during DDL unless the
* plugin has asked for them.
*/
if (relation->rd_rel->relrewrite && !rb->output_rewrites)
goto change_done;
/*
* For now ignore sequence changes entirely. Most of the
* time they don't log changes using records we
* understand, so it doesn't make sense to handle the few
* cases we do.
*/
if (relation->rd_rel->relkind == RELKIND_SEQUENCE)
goto change_done;
/* user-triggered change */
if (!IsToastRelation(relation))
{
ReorderBufferToastReplace(rb, txn, relation, change);
rb->apply_change(rb, txn, relation, change);
/*
* Only clear reassembled toast chunks if we're sure
* they're not required anymore. The creator of the
* tuple tells us.
*/
if (change->data.tp.clear_toast_afterwards)
ReorderBufferToastReset(rb, txn);
}
/* we're not interested in toast deletions */
else if (change->action == REORDER_BUFFER_CHANGE_INSERT)
{
/*
* Need to reassemble the full toasted Datum in
* memory, to ensure the chunks don't get reused till
* we're done remove it from the list of this
* transaction's changes. Otherwise it will get
* freed/reused while restoring spooled data from
* disk.
*/
Assert(change->data.tp.newtuple != NULL);
dlist_delete(&change->node);
ReorderBufferToastAppendChunk(rb, txn, relation,
change);
}
change_done:
/*
* Either speculative insertion was confirmed, or it was
* unsuccessful and the record isn't needed anymore.
*/
if (specinsert != NULL)
{
ReorderBufferReturnChange(rb, specinsert);
specinsert = NULL;
}
if (relation != NULL)
{
RelationClose(relation);
relation = NULL;
}
break;
case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT:
/*
* Speculative insertions are dealt with by delaying the
* processing of the insert until the confirmation record
* arrives. For that we simply unlink the record from the
* chain, so it does not get freed/reused while restoring
* spooled data from disk.
*
* This is safe in the face of concurrent catalog changes
* because the relevant relation can't be changed between
* speculative insertion and confirmation due to
* CheckTableNotInUse() and locking.
*/
/* clear out a pending (and thus failed) speculation */
if (specinsert != NULL)
{
ReorderBufferReturnChange(rb, specinsert);
specinsert = NULL;
}
/* and memorize the pending insertion */
dlist_delete(&change->node);
specinsert = change;
break;
case REORDER_BUFFER_CHANGE_TRUNCATE:
{
int i;
int nrelids = change->data.truncate.nrelids;
int nrelations = 0;
Relation *relations;
relations = palloc0(nrelids * sizeof(Relation));
for (i = 0; i < nrelids; i++)
{
Oid relid = change->data.truncate.relids[i];
Relation relation;
relation = RelationIdGetRelation(relid);
if (relation == NULL)
elog(ERROR, "could not open relation with OID %u", relid);
if (!RelationIsLogicallyLogged(relation))
continue;
relations[nrelations++] = relation;
}
rb->apply_truncate(rb, txn, nrelations, relations, change);
for (i = 0; i < nrelations; i++)
RelationClose(relations[i]);
break;
}
case REORDER_BUFFER_CHANGE_MESSAGE:
rb->message(rb, txn, change->lsn, true,
change->data.msg.prefix,
change->data.msg.message_size,
change->data.msg.message);
break;
case REORDER_BUFFER_CHANGE_INTERNAL_SNAPSHOT:
/* get rid of the old */
TeardownHistoricSnapshot(false);
if (snapshot_now->copied)
{
ReorderBufferFreeSnap(rb, snapshot_now);
snapshot_now =
ReorderBufferCopySnap(rb, change->data.snapshot,
txn, command_id);
}
/*
* Restored from disk, need to be careful not to double
* free. We could introduce refcounting for that, but for
* now this seems infrequent enough not to care.
*/
else if (change->data.snapshot->copied)
{
snapshot_now =
ReorderBufferCopySnap(rb, change->data.snapshot,
txn, command_id);
}
else
{
snapshot_now = change->data.snapshot;
}
/* and continue with the new one */
SetupHistoricSnapshot(snapshot_now, txn->tuplecid_hash);
break;
case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
Assert(change->data.command_id != InvalidCommandId);
if (command_id < change->data.command_id)
{
command_id = change->data.command_id;
if (!snapshot_now->copied)
{
/* we don't use the global one anymore */
snapshot_now = ReorderBufferCopySnap(rb, snapshot_now,
txn, command_id);
}
snapshot_now->curcid = command_id;
TeardownHistoricSnapshot(false);
SetupHistoricSnapshot(snapshot_now, txn->tuplecid_hash);
/*
* Every time the CommandId is incremented, we could
* see new catalog contents, so execute all
* invalidations.
*/
ReorderBufferExecuteInvalidations(rb, txn);
}
break;
case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
elog(ERROR, "tuplecid value in changequeue");
break;
}
}
/*
* There's a speculative insertion remaining, just clean in up, it
* can't have been successful, otherwise we'd gotten a confirmation
* record.
*/
if (specinsert)
{
ReorderBufferReturnChange(rb, specinsert);
specinsert = NULL;
}
/* clean up the iterator */
ReorderBufferIterTXNFinish(rb, iterstate);
iterstate = NULL;
/* call commit callback */
rb->commit(rb, txn, commit_lsn);
/* this is just a sanity check against bad output plugin behaviour */
if (GetCurrentTransactionIdIfAny() != InvalidTransactionId)
elog(ERROR, "output plugin used XID %u",
GetCurrentTransactionId());
/* cleanup */
TeardownHistoricSnapshot(false);
/*
* Aborting the current (sub-)transaction as a whole has the right
* semantics. We want all locks acquired in here to be released, not
* reassigned to the parent and we do not want any database access
* have persistent effects.
*/
AbortCurrentTransaction();
/* make sure there's no cache pollution */
ReorderBufferExecuteInvalidations(rb, txn);
if (using_subtxn)
RollbackAndReleaseCurrentSubTransaction();
if (snapshot_now->copied)
ReorderBufferFreeSnap(rb, snapshot_now);
/* remove potential on-disk data, and deallocate */
ReorderBufferCleanupTXN(rb, txn);
}
PG_CATCH();
{
/* TODO: Encapsulate cleanup from the PG_TRY and PG_CATCH blocks */
if (iterstate)
ReorderBufferIterTXNFinish(rb, iterstate);
TeardownHistoricSnapshot(true);
/*
* Force cache invalidation to happen outside of a valid transaction
* to prevent catalog access as we just caught an error.
*/
AbortCurrentTransaction();
/* make sure there's no cache pollution */
ReorderBufferExecuteInvalidations(rb, txn);
if (using_subtxn)
RollbackAndReleaseCurrentSubTransaction();
if (snapshot_now->copied)
ReorderBufferFreeSnap(rb, snapshot_now);
/* remove potential on-disk data, and deallocate */
ReorderBufferCleanupTXN(rb, txn);
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* Abort a transaction that possibly has previous changes. Needs to be first
* called for subtransactions and then for the toplevel xid.
*
* NB: Transactions handled here have to have actively aborted (i.e. have
* produced an abort record). Implicitly aborted transactions are handled via
* ReorderBufferAbortOld(); transactions we're just not interested in, but
* which have committed are handled in ReorderBufferForget().
*
* This function purges this transaction and its contents from memory and
* disk.
*/
void
ReorderBufferAbort(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
{
ReorderBufferTXN *txn;
txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr,
false);
/* unknown, nothing to remove */
if (txn == NULL)
return;
/* cosmetic... */
txn->final_lsn = lsn;
/* remove potential on-disk data, and deallocate */
ReorderBufferCleanupTXN(rb, txn);
}
/*
* Abort all transactions that aren't actually running anymore because the
* server restarted.
*
* NB: These really have to be transactions that have aborted due to a server
* crash/immediate restart, as we don't deal with invalidations here.
*/
void
ReorderBufferAbortOld(ReorderBuffer *rb, TransactionId oldestRunningXid)
{
dlist_mutable_iter it;
/*
* Iterate through all (potential) toplevel TXNs and abort all that are
* older than what possibly can be running. Once we've found the first
* that is alive we stop, there might be some that acquired an xid earlier
* but started writing later, but it's unlikely and they will be cleaned
* up in a later call to this function.
*/
dlist_foreach_modify(it, &rb->toplevel_by_lsn)
{
ReorderBufferTXN *txn;
txn = dlist_container(ReorderBufferTXN, node, it.cur);
if (TransactionIdPrecedes(txn->xid, oldestRunningXid))
{
/*
* We set final_lsn on a transaction when we decode its commit or
* abort record, but we never see those records for crashed
* transactions. To ensure cleanup of these transactions, set
* final_lsn to that of their last change; this causes
* ReorderBufferRestoreCleanup to do the right thing.
*/
if (txn->serialized && txn->final_lsn == 0)
{
ReorderBufferChange *last =
dlist_tail_element(ReorderBufferChange, node, &txn->changes);
txn->final_lsn = last->lsn;
}
elog(DEBUG2, "aborting old transaction %u", txn->xid);
/* remove potential on-disk data, and deallocate this tx */
ReorderBufferCleanupTXN(rb, txn);
}
else
return;
}
}
/*
* Forget the contents of a transaction if we aren't interested in its
* contents. Needs to be first called for subtransactions and then for the
* toplevel xid.
*
* This is significantly different to ReorderBufferAbort() because
* transactions that have committed need to be treated differently from aborted
* ones since they may have modified the catalog.
*
* Note that this is only allowed to be called in the moment a transaction
* commit has just been read, not earlier; otherwise later records referring
* to this xid might re-create the transaction incompletely.
*/
void
ReorderBufferForget(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
{
ReorderBufferTXN *txn;
txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr,
false);
/* unknown, nothing to forget */
if (txn == NULL)
return;
/* cosmetic... */
txn->final_lsn = lsn;
/*
* Process cache invalidation messages if there are any. Even if we're not
* interested in the transaction's contents, it could have manipulated the
* catalog and we need to update the caches according to that.
*/
if (txn->base_snapshot != NULL && txn->ninvalidations > 0)
ReorderBufferImmediateInvalidation(rb, txn->ninvalidations,
txn->invalidations);
else
Assert(txn->ninvalidations == 0);
/* remove potential on-disk data, and deallocate */
ReorderBufferCleanupTXN(rb, txn);
}
/*
* Execute invalidations happening outside the context of a decoded
* transaction. That currently happens either for xid-less commits
* (cf. RecordTransactionCommit()) or for invalidations in uninteresting
* transactions (via ReorderBufferForget()).
*/
void
ReorderBufferImmediateInvalidation(ReorderBuffer *rb, uint32 ninvalidations,
SharedInvalidationMessage *invalidations)
{
bool use_subtxn = IsTransactionOrTransactionBlock();
int i;
if (use_subtxn)
BeginInternalSubTransaction("replay");
/*
* Force invalidations to happen outside of a valid transaction - that way
* entries will just be marked as invalid without accessing the catalog.
* That's advantageous because we don't need to setup the full state
* necessary for catalog access.
*/
if (use_subtxn)
AbortCurrentTransaction();
for (i = 0; i < ninvalidations; i++)
LocalExecuteInvalidationMessage(&invalidations[i]);
if (use_subtxn)
RollbackAndReleaseCurrentSubTransaction();
}
/*
* Tell reorderbuffer about an xid seen in the WAL stream. Has to be called at
* least once for every xid in XLogRecord->xl_xid (other places in records
* may, but do not have to be passed through here).
*
* Reorderbuffer keeps some datastructures about transactions in LSN order,
* for efficiency. To do that it has to know about when transactions are seen
* first in the WAL. As many types of records are not actually interesting for
* logical decoding, they do not necessarily pass though here.
*/
void
ReorderBufferProcessXid(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
{
/* many records won't have an xid assigned, centralize check here */
if (xid != InvalidTransactionId)
ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
}
/*
* Add a new snapshot to this transaction that may only used after lsn 'lsn'
* because the previous snapshot doesn't describe the catalog correctly for
* following rows.
*/
void
ReorderBufferAddSnapshot(ReorderBuffer *rb, TransactionId xid,
XLogRecPtr lsn, Snapshot snap)
{
ReorderBufferChange *change = ReorderBufferGetChange(rb);
change->data.snapshot = snap;
change->action = REORDER_BUFFER_CHANGE_INTERNAL_SNAPSHOT;
ReorderBufferQueueChange(rb, xid, lsn, change);
}
/*
* Set up the transaction's base snapshot.
*
* If we know that xid is a subtransaction, set the base snapshot on the
* top-level transaction instead.
*/
void
ReorderBufferSetBaseSnapshot(ReorderBuffer *rb, TransactionId xid,
XLogRecPtr lsn, Snapshot snap)
{
ReorderBufferTXN *txn;
bool is_new;
AssertArg(snap != NULL);
/*
* Fetch the transaction to operate on. If we know it's a subtransaction,
* operate on its top-level transaction instead.
*/
txn = ReorderBufferTXNByXid(rb, xid, true, &is_new, lsn, true);
if (txn->is_known_as_subxact)
txn = ReorderBufferTXNByXid(rb, txn->toplevel_xid, false,
NULL, InvalidXLogRecPtr, false);
Assert(txn->base_snapshot == NULL);
txn->base_snapshot = snap;
txn->base_snapshot_lsn = lsn;
dlist_push_tail(&rb->txns_by_base_snapshot_lsn, &txn->base_snapshot_node);
AssertTXNLsnOrder(rb);
}
/*
* Access the catalog with this CommandId at this point in the changestream.
*
* May only be called for command ids > 1
*/
void
ReorderBufferAddNewCommandId(ReorderBuffer *rb, TransactionId xid,
XLogRecPtr lsn, CommandId cid)
{
ReorderBufferChange *change = ReorderBufferGetChange(rb);
change->data.command_id = cid;
change->action = REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID;
ReorderBufferQueueChange(rb, xid, lsn, change);
}
/*
* Add new (relfilenode, tid) -> (cmin, cmax) mappings.
*/
void
ReorderBufferAddNewTupleCids(ReorderBuffer *rb, TransactionId xid,
XLogRecPtr lsn, RelFileNode node,
ItemPointerData tid, CommandId cmin,
CommandId cmax, CommandId combocid)
{
ReorderBufferChange *change = ReorderBufferGetChange(rb);
ReorderBufferTXN *txn;
txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
change->data.tuplecid.node = node;
change->data.tuplecid.tid = tid;
change->data.tuplecid.cmin = cmin;
change->data.tuplecid.cmax = cmax;
change->data.tuplecid.combocid = combocid;
change->lsn = lsn;
change->action = REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID;
dlist_push_tail(&txn->tuplecids, &change->node);
txn->ntuplecids++;
}
/*
* Setup the invalidation of the toplevel transaction.
*
* This needs to be done before ReorderBufferCommit is called!
*/
void
ReorderBufferAddInvalidations(ReorderBuffer *rb, TransactionId xid,
XLogRecPtr lsn, Size nmsgs,
SharedInvalidationMessage *msgs)
{
ReorderBufferTXN *txn;
txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
if (txn->ninvalidations != 0)
elog(ERROR, "only ever add one set of invalidations");
Assert(nmsgs > 0);
txn->ninvalidations = nmsgs;
txn->invalidations = (SharedInvalidationMessage *)
MemoryContextAlloc(rb->context,
sizeof(SharedInvalidationMessage) * nmsgs);
memcpy(txn->invalidations, msgs,
sizeof(SharedInvalidationMessage) * nmsgs);
}
/*
* Apply all invalidations we know. Possibly we only need parts at this point
* in the changestream but we don't know which those are.
*/
static void
ReorderBufferExecuteInvalidations(ReorderBuffer *rb, ReorderBufferTXN *txn)
{
int i;
for (i = 0; i < txn->ninvalidations; i++)
LocalExecuteInvalidationMessage(&txn->invalidations[i]);
}
/*
* Mark a transaction as containing catalog changes
*/
void
ReorderBufferXidSetCatalogChanges(ReorderBuffer *rb, TransactionId xid,
XLogRecPtr lsn)
{
ReorderBufferTXN *txn;
txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
txn->has_catalog_changes = true;
}
/*
* Query whether a transaction is already *known* to contain catalog
* changes. This can be wrong until directly before the commit!
*/
bool
ReorderBufferXidHasCatalogChanges(ReorderBuffer *rb, TransactionId xid)
{
ReorderBufferTXN *txn;
txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr,
false);
if (txn == NULL)
return false;
return txn->has_catalog_changes;
}
/*
* ReorderBufferXidHasBaseSnapshot
* Have we already set the base snapshot for the given txn/subtxn?
*/
bool
ReorderBufferXidHasBaseSnapshot(ReorderBuffer *rb, TransactionId xid)
{
ReorderBufferTXN *txn;
txn = ReorderBufferTXNByXid(rb, xid, false,
NULL, InvalidXLogRecPtr, false);
/* transaction isn't known yet, ergo no snapshot */
if (txn == NULL)
return false;
/* a known subtxn? operate on top-level txn instead */
if (txn->is_known_as_subxact)
txn = ReorderBufferTXNByXid(rb, txn->toplevel_xid, false,
NULL, InvalidXLogRecPtr, false);
return txn->base_snapshot != NULL;
}
/*
* ---------------------------------------
* Disk serialization support
* ---------------------------------------
*/
/*
* Ensure the IO buffer is >= sz.
*/
static void
ReorderBufferSerializeReserve(ReorderBuffer *rb, Size sz)
{
if (!rb->outbufsize)
{
rb->outbuf = MemoryContextAlloc(rb->context, sz);
rb->outbufsize = sz;
}
else if (rb->outbufsize < sz)
{
rb->outbuf = repalloc(rb->outbuf, sz);
rb->outbufsize = sz;
}
}
/*
* Check whether the transaction tx should spill its data to disk.
*/
static void
ReorderBufferCheckSerializeTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
{
/*
* TODO: improve accounting so we cheaply can take subtransactions into
* account here.
*/
if (txn->nentries_mem >= max_changes_in_memory)
{
ReorderBufferSerializeTXN(rb, txn);
Assert(txn->nentries_mem == 0);
}
}
/*
* Spill data of a large transaction (and its subtransactions) to disk.
*/
static void
ReorderBufferSerializeTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
{
dlist_iter subtxn_i;
dlist_mutable_iter change_i;
int fd = -1;
XLogSegNo curOpenSegNo = 0;
Size spilled = 0;
elog(DEBUG2, "spill %u changes in XID %u to disk",
(uint32) txn->nentries_mem, txn->xid);
/* do the same to all child TXs */
dlist_foreach(subtxn_i, &txn->subtxns)
{
ReorderBufferTXN *subtxn;
subtxn = dlist_container(ReorderBufferTXN, node, subtxn_i.cur);
ReorderBufferSerializeTXN(rb, subtxn);
}
/* serialize changestream */
dlist_foreach_modify(change_i, &txn->changes)
{
ReorderBufferChange *change;
change = dlist_container(ReorderBufferChange, node, change_i.cur);
/*
* store in segment in which it belongs by start lsn, don't split over
* multiple segments tho
*/
if (fd == -1 ||
!XLByteInSeg(change->lsn, curOpenSegNo, wal_segment_size))
{
char path[MAXPGPATH];
if (fd != -1)
CloseTransientFile(fd);
XLByteToSeg(change->lsn, curOpenSegNo, wal_segment_size);
/*
* No need to care about TLIs here, only used during a single run,
* so each LSN only maps to a specific WAL record.
*/
ReorderBufferSerializedPath(path, MyReplicationSlot, txn->xid,
curOpenSegNo);
/* open segment, create it if necessary */
fd = OpenTransientFile(path,
O_CREAT | O_WRONLY | O_APPEND | PG_BINARY);
if (fd < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open file \"%s\": %m", path)));
}
ReorderBufferSerializeChange(rb, txn, fd, change);
dlist_delete(&change->node);
ReorderBufferReturnChange(rb, change);
spilled++;
}
Assert(spilled == txn->nentries_mem);
Assert(dlist_is_empty(&txn->changes));
txn->nentries_mem = 0;
txn->serialized = true;
if (fd != -1)
CloseTransientFile(fd);
}
/*
* Serialize individual change to disk.
*/
static void
ReorderBufferSerializeChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
int fd, ReorderBufferChange *change)
{
ReorderBufferDiskChange *ondisk;
Size sz = sizeof(ReorderBufferDiskChange);
ReorderBufferSerializeReserve(rb, sz);
ondisk = (ReorderBufferDiskChange *) rb->outbuf;
memcpy(&ondisk->change, change, sizeof(ReorderBufferChange));
switch (change->action)
{
/* fall through these, they're all similar enough */
case REORDER_BUFFER_CHANGE_INSERT:
case REORDER_BUFFER_CHANGE_UPDATE:
case REORDER_BUFFER_CHANGE_DELETE:
case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT:
{
char *data;
ReorderBufferTupleBuf *oldtup,
*newtup;
Size oldlen = 0;
Size newlen = 0;
oldtup = change->data.tp.oldtuple;
newtup = change->data.tp.newtuple;
if (oldtup)
{
sz += sizeof(HeapTupleData);
oldlen = oldtup->tuple.t_len;
sz += oldlen;
}
if (newtup)
{
sz += sizeof(HeapTupleData);
newlen = newtup->tuple.t_len;
sz += newlen;
}
/* make sure we have enough space */
ReorderBufferSerializeReserve(rb, sz);
data = ((char *) rb->outbuf) + sizeof(ReorderBufferDiskChange);
/* might have been reallocated above */
ondisk = (ReorderBufferDiskChange *) rb->outbuf;
if (oldlen)
{
memcpy(data, &oldtup->tuple, sizeof(HeapTupleData));
data += sizeof(HeapTupleData);
memcpy(data, oldtup->tuple.t_data, oldlen);
data += oldlen;
}
if (newlen)
{
memcpy(data, &newtup->tuple, sizeof(HeapTupleData));
data += sizeof(HeapTupleData);
memcpy(data, newtup->tuple.t_data, newlen);
data += newlen;
}
break;
}
case REORDER_BUFFER_CHANGE_MESSAGE:
{
char *data;
Size prefix_size = strlen(change->data.msg.prefix) + 1;
sz += prefix_size + change->data.msg.message_size +
sizeof(Size) + sizeof(Size);
ReorderBufferSerializeReserve(rb, sz);
data = ((char *) rb->outbuf) + sizeof(ReorderBufferDiskChange);
/* might have been reallocated above */
ondisk = (ReorderBufferDiskChange *) rb->outbuf;
/* write the prefix including the size */
memcpy(data, &prefix_size, sizeof(Size));
data += sizeof(Size);
memcpy(data, change->data.msg.prefix,
prefix_size);
data += prefix_size;
/* write the message including the size */
memcpy(data, &change->data.msg.message_size, sizeof(Size));
data += sizeof(Size);
memcpy(data, change->data.msg.message,
change->data.msg.message_size);
data += change->data.msg.message_size;
break;
}
case REORDER_BUFFER_CHANGE_INTERNAL_SNAPSHOT:
{
Snapshot snap;
char *data;
snap = change->data.snapshot;
sz += sizeof(SnapshotData) +
sizeof(TransactionId) * snap->xcnt +
sizeof(TransactionId) * snap->subxcnt
;
/* make sure we have enough space */
ReorderBufferSerializeReserve(rb, sz);
data = ((char *) rb->outbuf) + sizeof(ReorderBufferDiskChange);
/* might have been reallocated above */
ondisk = (ReorderBufferDiskChange *) rb->outbuf;
memcpy(data, snap, sizeof(SnapshotData));
data += sizeof(SnapshotData);
if (snap->xcnt)
{
memcpy(data, snap->xip,
sizeof(TransactionId) * snap->xcnt);
data += sizeof(TransactionId) * snap->xcnt;
}
if (snap->subxcnt)
{
memcpy(data, snap->subxip,
sizeof(TransactionId) * snap->subxcnt);
data += sizeof(TransactionId) * snap->subxcnt;
}
break;
}
case REORDER_BUFFER_CHANGE_TRUNCATE:
{
Size size;
char *data;
/* account for the OIDs of truncated relations */
size = sizeof(Oid) * change->data.truncate.nrelids;
sz += size;
/* make sure we have enough space */
ReorderBufferSerializeReserve(rb, sz);
data = ((char *) rb->outbuf) + sizeof(ReorderBufferDiskChange);
/* might have been reallocated above */
ondisk = (ReorderBufferDiskChange *) rb->outbuf;
memcpy(data, change->data.truncate.relids, size);
data += size;
break;
}
case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
/* ReorderBufferChange contains everything important */
break;
}
ondisk->size = sz;
errno = 0;
pgstat_report_wait_start(WAIT_EVENT_REORDER_BUFFER_WRITE);
if (write(fd, rb->outbuf, ondisk->size) != ondisk->size)
{
int save_errno = errno;
CloseTransientFile(fd);
/* if write didn't set errno, assume problem is no disk space */
errno = save_errno ? save_errno : ENOSPC;
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not write to data file for XID %u: %m",
txn->xid)));
}
pgstat_report_wait_end();
Assert(ondisk->change.action == change->action);
}
/*
* Restore a number of changes spilled to disk back into memory.
*/
static Size
ReorderBufferRestoreChanges(ReorderBuffer *rb, ReorderBufferTXN *txn,
int *fd, XLogSegNo *segno)
{
Size restored = 0;
XLogSegNo last_segno;
dlist_mutable_iter cleanup_iter;
Assert(txn->first_lsn != InvalidXLogRecPtr);
Assert(txn->final_lsn != InvalidXLogRecPtr);
/* free current entries, so we have memory for more */
dlist_foreach_modify(cleanup_iter, &txn->changes)
{
ReorderBufferChange *cleanup =
dlist_container(ReorderBufferChange, node, cleanup_iter.cur);
dlist_delete(&cleanup->node);
ReorderBufferReturnChange(rb, cleanup);
}
txn->nentries_mem = 0;
Assert(dlist_is_empty(&txn->changes));
XLByteToSeg(txn->final_lsn, last_segno, wal_segment_size);
while (restored < max_changes_in_memory && *segno <= last_segno)
{
int readBytes;
ReorderBufferDiskChange *ondisk;
if (*fd == -1)
{
char path[MAXPGPATH];
/* first time in */
if (*segno == 0)
XLByteToSeg(txn->first_lsn, *segno, wal_segment_size);
Assert(*segno != 0 || dlist_is_empty(&txn->changes));
/*
* No need to care about TLIs here, only used during a single run,
* so each LSN only maps to a specific WAL record.
*/
ReorderBufferSerializedPath(path, MyReplicationSlot, txn->xid,
*segno);
*fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
if (*fd < 0 && errno == ENOENT)
{
*fd = -1;
(*segno)++;
continue;
}
else if (*fd < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open file \"%s\": %m",
path)));
}
/*
* Read the statically sized part of a change which has information
* about the total size. If we couldn't read a record, we're at the
* end of this file.
*/
ReorderBufferSerializeReserve(rb, sizeof(ReorderBufferDiskChange));
pgstat_report_wait_start(WAIT_EVENT_REORDER_BUFFER_READ);
readBytes = read(*fd, rb->outbuf, sizeof(ReorderBufferDiskChange));
pgstat_report_wait_end();
/* eof */
if (readBytes == 0)
{
CloseTransientFile(*fd);
*fd = -1;
(*segno)++;
continue;
}
else if (readBytes < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from reorderbuffer spill file: %m")));
else if (readBytes != sizeof(ReorderBufferDiskChange))
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from reorderbuffer spill file: read %d instead of %u bytes",
readBytes,
(uint32) sizeof(ReorderBufferDiskChange))));
ondisk = (ReorderBufferDiskChange *) rb->outbuf;
ReorderBufferSerializeReserve(rb,
sizeof(ReorderBufferDiskChange) + ondisk->size);
ondisk = (ReorderBufferDiskChange *) rb->outbuf;
pgstat_report_wait_start(WAIT_EVENT_REORDER_BUFFER_READ);
readBytes = read(*fd, rb->outbuf + sizeof(ReorderBufferDiskChange),
ondisk->size - sizeof(ReorderBufferDiskChange));
pgstat_report_wait_end();
if (readBytes < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from reorderbuffer spill file: %m")));
else if (readBytes != ondisk->size - sizeof(ReorderBufferDiskChange))
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from reorderbuffer spill file: read %d instead of %u bytes",
readBytes,
(uint32) (ondisk->size - sizeof(ReorderBufferDiskChange)))));
/*
* ok, read a full change from disk, now restore it into proper
* in-memory format
*/
ReorderBufferRestoreChange(rb, txn, rb->outbuf);
restored++;
}
return restored;
}
/*
* Convert change from its on-disk format to in-memory format and queue it onto
* the TXN's ->changes list.
*
* Note: although "data" is declared char*, at entry it points to a
* maxalign'd buffer, making it safe in most of this function to assume
* that the pointed-to data is suitably aligned for direct access.
*/
static void
ReorderBufferRestoreChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
char *data)
{
ReorderBufferDiskChange *ondisk;
ReorderBufferChange *change;
ondisk = (ReorderBufferDiskChange *) data;
change = ReorderBufferGetChange(rb);
/* copy static part */
memcpy(change, &ondisk->change, sizeof(ReorderBufferChange));
data += sizeof(ReorderBufferDiskChange);
/* restore individual stuff */
switch (change->action)
{
/* fall through these, they're all similar enough */
case REORDER_BUFFER_CHANGE_INSERT:
case REORDER_BUFFER_CHANGE_UPDATE:
case REORDER_BUFFER_CHANGE_DELETE:
case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT:
if (change->data.tp.oldtuple)
{
uint32 tuplelen = ((HeapTuple) data)->t_len;
change->data.tp.oldtuple =
ReorderBufferGetTupleBuf(rb, tuplelen - SizeofHeapTupleHeader);
/* restore ->tuple */
memcpy(&change->data.tp.oldtuple->tuple, data,
sizeof(HeapTupleData));
data += sizeof(HeapTupleData);
/* reset t_data pointer into the new tuplebuf */
change->data.tp.oldtuple->tuple.t_data =
ReorderBufferTupleBufData(change->data.tp.oldtuple);
/* restore tuple data itself */
memcpy(change->data.tp.oldtuple->tuple.t_data, data, tuplelen);
data += tuplelen;
}
if (change->data.tp.newtuple)
{
/* here, data might not be suitably aligned! */
uint32 tuplelen;
memcpy(&tuplelen, data + offsetof(HeapTupleData, t_len),
sizeof(uint32));
change->data.tp.newtuple =
ReorderBufferGetTupleBuf(rb, tuplelen - SizeofHeapTupleHeader);
/* restore ->tuple */
memcpy(&change->data.tp.newtuple->tuple, data,
sizeof(HeapTupleData));
data += sizeof(HeapTupleData);
/* reset t_data pointer into the new tuplebuf */
change->data.tp.newtuple->tuple.t_data =
ReorderBufferTupleBufData(change->data.tp.newtuple);
/* restore tuple data itself */
memcpy(change->data.tp.newtuple->tuple.t_data, data, tuplelen);
data += tuplelen;
}
break;
case REORDER_BUFFER_CHANGE_MESSAGE:
{
Size prefix_size;
/* read prefix */
memcpy(&prefix_size, data, sizeof(Size));
data += sizeof(Size);
change->data.msg.prefix = MemoryContextAlloc(rb->context,
prefix_size);
memcpy(change->data.msg.prefix, data, prefix_size);
Assert(change->data.msg.prefix[prefix_size - 1] == '\0');
data += prefix_size;
/* read the message */
memcpy(&change->data.msg.message_size, data, sizeof(Size));
data += sizeof(Size);
change->data.msg.message = MemoryContextAlloc(rb->context,
change->data.msg.message_size);
memcpy(change->data.msg.message, data,
change->data.msg.message_size);
data += change->data.msg.message_size;
break;
}
case REORDER_BUFFER_CHANGE_INTERNAL_SNAPSHOT:
{
Snapshot oldsnap;
Snapshot newsnap;
Size size;
oldsnap = (Snapshot) data;
size = sizeof(SnapshotData) +
sizeof(TransactionId) * oldsnap->xcnt +
sizeof(TransactionId) * (oldsnap->subxcnt + 0);
change->data.snapshot = MemoryContextAllocZero(rb->context, size);
newsnap = change->data.snapshot;
memcpy(newsnap, data, size);
newsnap->xip = (TransactionId *)
(((char *) newsnap) + sizeof(SnapshotData));
newsnap->subxip = newsnap->xip + newsnap->xcnt;
newsnap->copied = true;
break;
}
/* the base struct contains all the data, easy peasy */
case REORDER_BUFFER_CHANGE_TRUNCATE:
{
Oid *relids;
relids = ReorderBufferGetRelids(rb,
change->data.truncate.nrelids);
memcpy(relids, data, change->data.truncate.nrelids * sizeof(Oid));
change->data.truncate.relids = relids;
break;
}
case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
break;
}
dlist_push_tail(&txn->changes, &change->node);
txn->nentries_mem++;
}
/*
* Remove all on-disk stored for the passed in transaction.
*/
static void
ReorderBufferRestoreCleanup(ReorderBuffer *rb, ReorderBufferTXN *txn)
{
XLogSegNo first;
XLogSegNo cur;
XLogSegNo last;
Assert(txn->first_lsn != InvalidXLogRecPtr);
Assert(txn->final_lsn != InvalidXLogRecPtr);
XLByteToSeg(txn->first_lsn, first, wal_segment_size);
XLByteToSeg(txn->final_lsn, last, wal_segment_size);
/* iterate over all possible filenames, and delete them */
for (cur = first; cur <= last; cur++)
{
char path[MAXPGPATH];
ReorderBufferSerializedPath(path, MyReplicationSlot, txn->xid, cur);
if (unlink(path) != 0 && errno != ENOENT)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not remove file \"%s\": %m", path)));
}
}
/*
* Remove any leftover serialized reorder buffers from a slot directory after a
* prior crash or decoding session exit.
*/
static void
ReorderBufferCleanupSerializedTXNs(const char *slotname)
{
DIR *spill_dir;
struct dirent *spill_de;
struct stat statbuf;
char path[MAXPGPATH * 2 + 12];
sprintf(path, "pg_replslot/%s", slotname);
/* we're only handling directories here, skip if it's not ours */
if (lstat(path, &statbuf) == 0 && !S_ISDIR(statbuf.st_mode))
return;
spill_dir = AllocateDir(path);
while ((spill_de = ReadDirExtended(spill_dir, path, INFO)) != NULL)
{
/* only look at names that can be ours */
if (strncmp(spill_de->d_name, "xid", 3) == 0)
{
snprintf(path, sizeof(path),
"pg_replslot/%s/%s", slotname,
spill_de->d_name);
if (unlink(path) != 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not remove file \"%s\" during removal of pg_replslot/%s/xid*: %m",
path, slotname)));
}
}
FreeDir(spill_dir);
}
/*
* Given a replication slot, transaction ID and segment number, fill in the
* corresponding spill file into 'path', which is a caller-owned buffer of size
* at least MAXPGPATH.
*/
static void
ReorderBufferSerializedPath(char *path, ReplicationSlot *slot, TransactionId xid,
XLogSegNo segno)
{
XLogRecPtr recptr;
XLogSegNoOffsetToRecPtr(segno, 0, wal_segment_size, recptr);
snprintf(path, MAXPGPATH, "pg_replslot/%s/xid-%u-lsn-%X-%X.spill",
NameStr(MyReplicationSlot->data.name),
xid,
(uint32) (recptr >> 32), (uint32) recptr);
}
/*
* Delete all data spilled to disk after we've restarted/crashed. It will be
* recreated when the respective slots are reused.
*/
void
StartupReorderBuffer(void)
{
DIR *logical_dir;
struct dirent *logical_de;
logical_dir = AllocateDir("pg_replslot");
while ((logical_de = ReadDir(logical_dir, "pg_replslot")) != NULL)
{
if (strcmp(logical_de->d_name, ".") == 0 ||
strcmp(logical_de->d_name, "..") == 0)
continue;
/* if it cannot be a slot, skip the directory */
if (!ReplicationSlotValidateName(logical_de->d_name, DEBUG2))
continue;
/*
* ok, has to be a surviving logical slot, iterate and delete
* everything starting with xid-*
*/
ReorderBufferCleanupSerializedTXNs(logical_de->d_name);
}
FreeDir(logical_dir);
}
/* ---------------------------------------
* toast reassembly support
* ---------------------------------------
*/
/*
* Initialize per tuple toast reconstruction support.
*/
static void
ReorderBufferToastInitHash(ReorderBuffer *rb, ReorderBufferTXN *txn)
{
HASHCTL hash_ctl;
Assert(txn->toast_hash == NULL);
memset(&hash_ctl, 0, sizeof(hash_ctl));
hash_ctl.keysize = sizeof(Oid);
hash_ctl.entrysize = sizeof(ReorderBufferToastEnt);
hash_ctl.hcxt = rb->context;
txn->toast_hash = hash_create("ReorderBufferToastHash", 5, &hash_ctl,
HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
}
/*
* Per toast-chunk handling for toast reconstruction
*
* Appends a toast chunk so we can reconstruct it when the tuple "owning" the
* toasted Datum comes along.
*/
static void
ReorderBufferToastAppendChunk(ReorderBuffer *rb, ReorderBufferTXN *txn,
Relation relation, ReorderBufferChange *change)
{
ReorderBufferToastEnt *ent;
ReorderBufferTupleBuf *newtup;
bool found;
int32 chunksize;
bool isnull;
Pointer chunk;
TupleDesc desc = RelationGetDescr(relation);
Oid chunk_id;
int32 chunk_seq;
if (txn->toast_hash == NULL)
ReorderBufferToastInitHash(rb, txn);
Assert(IsToastRelation(relation));
newtup = change->data.tp.newtuple;
chunk_id = DatumGetObjectId(fastgetattr(&newtup->tuple, 1, desc, &isnull));
Assert(!isnull);
chunk_seq = DatumGetInt32(fastgetattr(&newtup->tuple, 2, desc, &isnull));
Assert(!isnull);
ent = (ReorderBufferToastEnt *)
hash_search(txn->toast_hash,
(void *) &chunk_id,
HASH_ENTER,
&found);
if (!found)
{
Assert(ent->chunk_id == chunk_id);
ent->num_chunks = 0;
ent->last_chunk_seq = 0;
ent->size = 0;
ent->reconstructed = NULL;
dlist_init(&ent->chunks);
if (chunk_seq != 0)
elog(ERROR, "got sequence entry %d for toast chunk %u instead of seq 0",
chunk_seq, chunk_id);
}
else if (found && chunk_seq != ent->last_chunk_seq + 1)
elog(ERROR, "got sequence entry %d for toast chunk %u instead of seq %d",
chunk_seq, chunk_id, ent->last_chunk_seq + 1);
chunk = DatumGetPointer(fastgetattr(&newtup->tuple, 3, desc, &isnull));
Assert(!isnull);
/* calculate size so we can allocate the right size at once later */
if (!VARATT_IS_EXTENDED(chunk))
chunksize = VARSIZE(chunk) - VARHDRSZ;
else if (VARATT_IS_SHORT(chunk))
/* could happen due to heap_form_tuple doing its thing */
chunksize = VARSIZE_SHORT(chunk) - VARHDRSZ_SHORT;
else
elog(ERROR, "unexpected type of toast chunk");
ent->size += chunksize;
ent->last_chunk_seq = chunk_seq;
ent->num_chunks++;
dlist_push_tail(&ent->chunks, &change->node);
}
/*
* Rejigger change->newtuple to point to in-memory toast tuples instead to
* on-disk toast tuples that may not longer exist (think DROP TABLE or VACUUM).
*
* We cannot replace unchanged toast tuples though, so those will still point
* to on-disk toast data.
*/
static void
ReorderBufferToastReplace(ReorderBuffer *rb, ReorderBufferTXN *txn,
Relation relation, ReorderBufferChange *change)
{
TupleDesc desc;
int natt;
Datum *attrs;
bool *isnull;
bool *free;
HeapTuple tmphtup;
Relation toast_rel;
TupleDesc toast_desc;
MemoryContext oldcontext;
ReorderBufferTupleBuf *newtup;
/* no toast tuples changed */
if (txn->toast_hash == NULL)
return;
oldcontext = MemoryContextSwitchTo(rb->context);
/* we should only have toast tuples in an INSERT or UPDATE */
Assert(change->data.tp.newtuple);
desc = RelationGetDescr(relation);
toast_rel = RelationIdGetRelation(relation->rd_rel->reltoastrelid);
toast_desc = RelationGetDescr(toast_rel);
/* should we allocate from stack instead? */
attrs = palloc0(sizeof(Datum) * desc->natts);
isnull = palloc0(sizeof(bool) * desc->natts);
free = palloc0(sizeof(bool) * desc->natts);
newtup = change->data.tp.newtuple;
heap_deform_tuple(&newtup->tuple, desc, attrs, isnull);
for (natt = 0; natt < desc->natts; natt++)
{
Form_pg_attribute attr = TupleDescAttr(desc, natt);
ReorderBufferToastEnt *ent;
struct varlena *varlena;
/* va_rawsize is the size of the original datum -- including header */
struct varatt_external toast_pointer;
struct varatt_indirect redirect_pointer;
struct varlena *new_datum = NULL;
struct varlena *reconstructed;
dlist_iter it;
Size data_done = 0;
/* system columns aren't toasted */
if (attr->attnum < 0)
continue;
if (attr->attisdropped)
continue;
/* not a varlena datatype */
if (attr->attlen != -1)
continue;
/* no data */
if (isnull[natt])
continue;
/* ok, we know we have a toast datum */
varlena = (struct varlena *) DatumGetPointer(attrs[natt]);
/* no need to do anything if the tuple isn't external */
if (!VARATT_IS_EXTERNAL(varlena))
continue;
VARATT_EXTERNAL_GET_POINTER(toast_pointer, varlena);
/*
* Check whether the toast tuple changed, replace if so.
*/
ent = (ReorderBufferToastEnt *)
hash_search(txn->toast_hash,
(void *) &toast_pointer.va_valueid,
HASH_FIND,
NULL);
if (ent == NULL)
continue;
new_datum =
(struct varlena *) palloc0(INDIRECT_POINTER_SIZE);
free[natt] = true;
reconstructed = palloc0(toast_pointer.va_rawsize);
ent->reconstructed = reconstructed;
/* stitch toast tuple back together from its parts */
dlist_foreach(it, &ent->chunks)
{
bool isnull;
ReorderBufferChange *cchange;
ReorderBufferTupleBuf *ctup;
Pointer chunk;
cchange = dlist_container(ReorderBufferChange, node, it.cur);
ctup = cchange->data.tp.newtuple;
chunk = DatumGetPointer(
fastgetattr(&ctup->tuple, 3, toast_desc, &isnull));
Assert(!isnull);
Assert(!VARATT_IS_EXTERNAL(chunk));
Assert(!VARATT_IS_SHORT(chunk));
memcpy(VARDATA(reconstructed) + data_done,
VARDATA(chunk),
VARSIZE(chunk) - VARHDRSZ);
data_done += VARSIZE(chunk) - VARHDRSZ;
}
Assert(data_done == toast_pointer.va_extsize);
/* make sure its marked as compressed or not */
if (VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer))
SET_VARSIZE_COMPRESSED(reconstructed, data_done + VARHDRSZ);
else
SET_VARSIZE(reconstructed, data_done + VARHDRSZ);
memset(&redirect_pointer, 0, sizeof(redirect_pointer));
redirect_pointer.pointer = reconstructed;
SET_VARTAG_EXTERNAL(new_datum, VARTAG_INDIRECT);
memcpy(VARDATA_EXTERNAL(new_datum), &redirect_pointer,
sizeof(redirect_pointer));
attrs[natt] = PointerGetDatum(new_datum);
}
/*
* Build tuple in separate memory & copy tuple back into the tuplebuf
* passed to the output plugin. We can't directly heap_fill_tuple() into
* the tuplebuf because attrs[] will point back into the current content.
*/
tmphtup = heap_form_tuple(desc, attrs, isnull);
Assert(newtup->tuple.t_len <= MaxHeapTupleSize);
Assert(ReorderBufferTupleBufData(newtup) == newtup->tuple.t_data);
memcpy(newtup->tuple.t_data, tmphtup->t_data, tmphtup->t_len);
newtup->tuple.t_len = tmphtup->t_len;
/*
* free resources we won't further need, more persistent stuff will be
* free'd in ReorderBufferToastReset().
*/
RelationClose(toast_rel);
pfree(tmphtup);
for (natt = 0; natt < desc->natts; natt++)
{
if (free[natt])
pfree(DatumGetPointer(attrs[natt]));
}
pfree(attrs);
pfree(free);
pfree(isnull);
MemoryContextSwitchTo(oldcontext);
}
/*
* Free all resources allocated for toast reconstruction.
*/
static void
ReorderBufferToastReset(ReorderBuffer *rb, ReorderBufferTXN *txn)
{
HASH_SEQ_STATUS hstat;
ReorderBufferToastEnt *ent;
if (txn->toast_hash == NULL)
return;
/* sequentially walk over the hash and free everything */
hash_seq_init(&hstat, txn->toast_hash);
while ((ent = (ReorderBufferToastEnt *) hash_seq_search(&hstat)) != NULL)
{
dlist_mutable_iter it;
if (ent->reconstructed != NULL)
pfree(ent->reconstructed);
dlist_foreach_modify(it, &ent->chunks)
{
ReorderBufferChange *change =
dlist_container(ReorderBufferChange, node, it.cur);
dlist_delete(&change->node);
ReorderBufferReturnChange(rb, change);
}
}
hash_destroy(txn->toast_hash);
txn->toast_hash = NULL;
}
/* ---------------------------------------
* Visibility support for logical decoding
*
*
* Lookup actual cmin/cmax values when using decoding snapshot. We can't
* always rely on stored cmin/cmax values because of two scenarios:
*
* * A tuple got changed multiple times during a single transaction and thus
* has got a combocid. Combocid's are only valid for the duration of a
* single transaction.
* * A tuple with a cmin but no cmax (and thus no combocid) got
* deleted/updated in another transaction than the one which created it
* which we are looking at right now. As only one of cmin, cmax or combocid
* is actually stored in the heap we don't have access to the value we
* need anymore.
*
* To resolve those problems we have a per-transaction hash of (cmin,
* cmax) tuples keyed by (relfilenode, ctid) which contains the actual
* (cmin, cmax) values. That also takes care of combocids by simply
* not caring about them at all. As we have the real cmin/cmax values
* combocids aren't interesting.
*
* As we only care about catalog tuples here the overhead of this
* hashtable should be acceptable.
*
* Heap rewrites complicate this a bit, check rewriteheap.c for
* details.
* -------------------------------------------------------------------------
*/
/* struct for sorting mapping files by LSN efficiently */
typedef struct RewriteMappingFile
{
XLogRecPtr lsn;
char fname[MAXPGPATH];
} RewriteMappingFile;
#if NOT_USED
static void
DisplayMapping(HTAB *tuplecid_data)
{
HASH_SEQ_STATUS hstat;
ReorderBufferTupleCidEnt *ent;
hash_seq_init(&hstat, tuplecid_data);
while ((ent = (ReorderBufferTupleCidEnt *) hash_seq_search(&hstat)) != NULL)
{
elog(DEBUG3, "mapping: node: %u/%u/%u tid: %u/%u cmin: %u, cmax: %u",
ent->key.relnode.dbNode,
ent->key.relnode.spcNode,
ent->key.relnode.relNode,
ItemPointerGetBlockNumber(&ent->key.tid),
ItemPointerGetOffsetNumber(&ent->key.tid),
ent->cmin,
ent->cmax
);
}
}
#endif
/*
* Apply a single mapping file to tuplecid_data.
*
* The mapping file has to have been verified to be a) committed b) for our
* transaction c) applied in LSN order.
*/
static void
ApplyLogicalMappingFile(HTAB *tuplecid_data, Oid relid, const char *fname)
{
char path[MAXPGPATH];
int fd;
int readBytes;
LogicalRewriteMappingData map;
sprintf(path, "pg_logical/mappings/%s", fname);
fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
if (fd < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open file \"%s\": %m", path)));
while (true)
{
ReorderBufferTupleCidKey key;
ReorderBufferTupleCidEnt *ent;
ReorderBufferTupleCidEnt *new_ent;
bool found;
/* be careful about padding */
memset(&key, 0, sizeof(ReorderBufferTupleCidKey));
/* read all mappings till the end of the file */
pgstat_report_wait_start(WAIT_EVENT_REORDER_LOGICAL_MAPPING_READ);
readBytes = read(fd, &map, sizeof(LogicalRewriteMappingData));
pgstat_report_wait_end();
if (readBytes < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read file \"%s\": %m",
path)));
else if (readBytes == 0) /* EOF */
break;
else if (readBytes != sizeof(LogicalRewriteMappingData))
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from file \"%s\": read %d instead of %d bytes",
path, readBytes,
(int32) sizeof(LogicalRewriteMappingData))));
key.relnode = map.old_node;
ItemPointerCopy(&map.old_tid,
&key.tid);
ent = (ReorderBufferTupleCidEnt *)
hash_search(tuplecid_data,
(void *) &key,
HASH_FIND,
NULL);
/* no existing mapping, no need to update */
if (!ent)
continue;
key.relnode = map.new_node;
ItemPointerCopy(&map.new_tid,
&key.tid);
new_ent = (ReorderBufferTupleCidEnt *)
hash_search(tuplecid_data,
(void *) &key,
HASH_ENTER,
&found);
if (found)
{
/*
* Make sure the existing mapping makes sense. We sometime update
* old records that did not yet have a cmax (e.g. pg_class' own
* entry while rewriting it) during rewrites, so allow that.
*/
Assert(ent->cmin == InvalidCommandId || ent->cmin == new_ent->cmin);
Assert(ent->cmax == InvalidCommandId || ent->cmax == new_ent->cmax);
}
else
{
/* update mapping */
new_ent->cmin = ent->cmin;
new_ent->cmax = ent->cmax;
new_ent->combocid = ent->combocid;
}
}
if (CloseTransientFile(fd) != 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not close file \"%s\": %m", path)));
}
/*
* Check whether the TransactionId 'xid' is in the pre-sorted array 'xip'.
*/
static bool
TransactionIdInArray(TransactionId xid, TransactionId *xip, Size num)
{
return bsearch(&xid, xip, num,
sizeof(TransactionId), xidComparator) != NULL;
}
/*
* list_sort() comparator for sorting RewriteMappingFiles in LSN order.
*/
static int
file_sort_by_lsn(const ListCell *a_p, const ListCell *b_p)
{
RewriteMappingFile *a = (RewriteMappingFile *) lfirst(a_p);
RewriteMappingFile *b = (RewriteMappingFile *) lfirst(b_p);
if (a->lsn < b->lsn)
return -1;
else if (a->lsn > b->lsn)
return 1;
return 0;
}
/*
* Apply any existing logical remapping files if there are any targeted at our
* transaction for relid.
*/
static void
UpdateLogicalMappings(HTAB *tuplecid_data, Oid relid, Snapshot snapshot)
{
DIR *mapping_dir;
struct dirent *mapping_de;
List *files = NIL;
ListCell *file;
Oid dboid = IsSharedRelation(relid) ? InvalidOid : MyDatabaseId;
mapping_dir = AllocateDir("pg_logical/mappings");
while ((mapping_de = ReadDir(mapping_dir, "pg_logical/mappings")) != NULL)
{
Oid f_dboid;
Oid f_relid;
TransactionId f_mapped_xid;
TransactionId f_create_xid;
XLogRecPtr f_lsn;
uint32 f_hi,
f_lo;
RewriteMappingFile *f;
if (strcmp(mapping_de->d_name, ".") == 0 ||
strcmp(mapping_de->d_name, "..") == 0)
continue;
/* Ignore files that aren't ours */
if (strncmp(mapping_de->d_name, "map-", 4) != 0)
continue;
if (sscanf(mapping_de->d_name, LOGICAL_REWRITE_FORMAT,
&f_dboid, &f_relid, &f_hi, &f_lo,
&f_mapped_xid, &f_create_xid) != 6)
elog(ERROR, "could not parse filename \"%s\"", mapping_de->d_name);
f_lsn = ((uint64) f_hi) << 32 | f_lo;
/* mapping for another database */
if (f_dboid != dboid)
continue;
/* mapping for another relation */
if (f_relid != relid)
continue;
/* did the creating transaction abort? */
if (!TransactionIdDidCommit(f_create_xid))
continue;
/* not for our transaction */
if (!TransactionIdInArray(f_mapped_xid, snapshot->subxip, snapshot->subxcnt))
continue;
/* ok, relevant, queue for apply */
f = palloc(sizeof(RewriteMappingFile));
f->lsn = f_lsn;
strcpy(f->fname, mapping_de->d_name);
files = lappend(files, f);
}
FreeDir(mapping_dir);
/* sort files so we apply them in LSN order */
list_sort(files, file_sort_by_lsn);
foreach(file, files)
{
RewriteMappingFile *f = (RewriteMappingFile *) lfirst(file);
elog(DEBUG1, "applying mapping: \"%s\" in %u", f->fname,
snapshot->subxip[0]);
ApplyLogicalMappingFile(tuplecid_data, relid, f->fname);
pfree(f);
}
}
/*
* Lookup cmin/cmax of a tuple, during logical decoding where we can't rely on
* combocids.
*/
bool
ResolveCminCmaxDuringDecoding(HTAB *tuplecid_data,
Snapshot snapshot,
HeapTuple htup, Buffer buffer,
CommandId *cmin, CommandId *cmax)
{
ReorderBufferTupleCidKey key;
ReorderBufferTupleCidEnt *ent;
ForkNumber forkno;
BlockNumber blockno;
bool updated_mapping = false;
/* be careful about padding */
memset(&key, 0, sizeof(key));
Assert(!BufferIsLocal(buffer));
/*
* get relfilenode from the buffer, no convenient way to access it other
* than that.
*/
BufferGetTag(buffer, &key.relnode, &forkno, &blockno);
/* tuples can only be in the main fork */
Assert(forkno == MAIN_FORKNUM);
Assert(blockno == ItemPointerGetBlockNumber(&htup->t_self));
ItemPointerCopy(&htup->t_self,
&key.tid);
restart:
ent = (ReorderBufferTupleCidEnt *)
hash_search(tuplecid_data,
(void *) &key,
HASH_FIND,
NULL);
/*
* failed to find a mapping, check whether the table was rewritten and
* apply mapping if so, but only do that once - there can be no new
* mappings while we are in here since we have to hold a lock on the
* relation.
*/
if (ent == NULL && !updated_mapping)
{
UpdateLogicalMappings(tuplecid_data, htup->t_tableOid, snapshot);
/* now check but don't update for a mapping again */
updated_mapping = true;
goto restart;
}
else if (ent == NULL)
return false;
if (cmin)
*cmin = ent->cmin;
if (cmax)
*cmax = ent->cmax;
return true;
}