diff options
Diffstat (limited to 'src/backend/commands/copy.c')
| -rw-r--r-- | src/backend/commands/copy.c | 58 |
1 files changed, 5 insertions, 53 deletions
diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c index fbde9f88e74..05f1fae6b03 100644 --- a/src/backend/commands/copy.c +++ b/src/backend/commands/copy.c @@ -2713,63 +2713,15 @@ CopyFrom(CopyState cstate) RelationGetRelationName(cstate->rel)))); } - /*---------- - * Check to see if we can avoid writing WAL - * - * If archive logging/streaming is not enabled *and* either - * - table was created in same transaction as this COPY - * - data is being written to relfilenode created in this transaction - * then we can skip writing WAL. It's safe because if the transaction - * doesn't commit, we'll discard the table (or the new relfilenode file). - * If it does commit, we'll have done the table_finish_bulk_insert() at - * the bottom of this routine first. - * - * As mentioned in comments in utils/rel.h, the in-same-transaction test - * is not always set correctly, since in rare cases rd_newRelfilenodeSubid - * can be cleared before the end of the transaction. The exact case is - * when a relation sets a new relfilenode twice in same transaction, yet - * the second one fails in an aborted subtransaction, e.g. - * - * BEGIN; - * TRUNCATE t; - * SAVEPOINT save; - * TRUNCATE t; - * ROLLBACK TO save; - * COPY ... - * - * Also, if the target file is new-in-transaction, we assume that checking - * FSM for free space is a waste of time, even if we must use WAL because - * of archiving. This could possibly be wrong, but it's unlikely. - * - * The comments for table_tuple_insert and RelationGetBufferForTuple - * specify that skipping WAL logging is only safe if we ensure that our - * tuples do not go into pages containing tuples from any other - * transactions --- but this must be the case if we have a new table or - * new relfilenode, so we need no additional work to enforce that. - * - * We currently don't support this optimization if the COPY target is a - * partitioned table as we currently only lazily initialize partition - * information when routing the first tuple to the partition. We cannot - * know at this stage if we can perform this optimization. It should be - * possible to improve on this, but it does mean maintaining heap insert - * option flags per partition and setting them when we first open the - * partition. - * - * This optimization is not supported for relation types which do not - * have any physical storage, with foreign tables and views using - * INSTEAD OF triggers entering in this category. Partitioned tables - * are not supported as per the description above. - *---------- + /* + * If the target file is new-in-transaction, we assume that checking FSM + * for free space is a waste of time. This could possibly be wrong, but + * it's unlikely. */ - /* createSubid is creation check, newRelfilenodeSubid is truncation check */ if (RELKIND_HAS_STORAGE(cstate->rel->rd_rel->relkind) && (cstate->rel->rd_createSubid != InvalidSubTransactionId || - cstate->rel->rd_newRelfilenodeSubid != InvalidSubTransactionId)) - { + cstate->rel->rd_firstRelfilenodeSubid != InvalidSubTransactionId)) ti_options |= TABLE_INSERT_SKIP_FSM; - if (!XLogIsNeeded()) - ti_options |= TABLE_INSERT_SKIP_WAL; - } /* * Optimize if new relfilenode was created in this subxact or one of its |