Merge prune, freeze and vacuum WAL record formats

The new combined WAL record is now used for pruning, freezing and 2nd
pass of vacuum. This is in preparation for changing VACUUM to write a
combined prune+freeze record per page, instead of separate two
records. The new WAL record format now supports that, but the code
still always writes separate records for pruning and freezing.

This reserves separate XLOG_HEAP2_* info codes for when the pruning
record is emitted for on-access pruning or VACUUM, per Peter
Geoghegan's suggestion. The record format is identical, but having
separate info codes makes it easier analyze pruning and vacuuming with
pg_waldump.

The function to emit the new WAL record, log_heap_prune_and_freeze(),
is in pruneheap.c. The existing heap_log_freeze_plan() and its
subroutines are moved to pruneheap.c without changes, to keep them
together with log_heap_prune_and_freeze().

Author: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://www.postgresql.org/message-id/CAAKRu_azf-zH%3DDgVbquZ3tFWjMY1w5pO8m-TXJaMdri8z3933g@mail.gmail.com
Discussion: https://www.postgresql.org/message-id/CAAKRu_b2oE4GL%3Dq4g9mcByS9yT7wTQvEH9OLpabj28e%2BWKFi2A@mail.gmail.com

1 files changed, 18 insertions, 1 deletions

diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 4b133f68593..368c570a0f4 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -211,6 +211,14 @@ typedef struct PruneResult
 	int8		htsv[MaxHeapTuplesPerPage + 1];
 } PruneResult;
 
+/* 'reason' codes for heap_page_prune() */
+typedef enum
+{
+	PRUNE_ON_ACCESS,			/* on-access pruning */
+	PRUNE_VACUUM_SCAN,			/* VACUUM 1st heap pass */
+	PRUNE_VACUUM_CLEANUP,		/* VACUUM 2nd heap pass */
+} PruneReason;
+
 /*
  * Pruning calculates tuple visibility once and saves the results in an array
  * of int8. See PruneResult.htsv for details. This helper function is meant to
@@ -322,12 +330,21 @@ extern void heap_page_prune(Relation relation, Buffer buffer,
 							struct GlobalVisState *vistest,
 							bool mark_unused_now,
 							PruneResult *presult,
+							PruneReason reason,
 							OffsetNumber *off_loc);
-extern void heap_page_prune_execute(Buffer buffer,
+extern void heap_page_prune_execute(Buffer buffer, bool lp_truncate_only,
 									OffsetNumber *redirected, int nredirected,
 									OffsetNumber *nowdead, int ndead,
 									OffsetNumber *nowunused, int nunused);
 extern void heap_get_root_tuples(Page page, OffsetNumber *root_offsets);
+extern void log_heap_prune_and_freeze(Relation relation, Buffer buffer,
+									  TransactionId conflict_xid,
+									  bool lp_truncate_only,
+									  PruneReason reason,
+									  HeapTupleFreeze *frozen, int nfrozen,
+									  OffsetNumber *redirected, int nredirected,
+									  OffsetNumber *dead, int ndead,
+									  OffsetNumber *unused, int nunused);
 
 /* in heap/vacuumlazy.c */
 struct VacuumParams;