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Skip WAL for new relfilenodes, under wal_level=minimal.

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Until now, only selected bulk operations (e.g. COPY) did this.  If a
given relfilenode received both a WAL-skipping COPY and a WAL-logged
operation (e.g. INSERT), recovery could lose tuples from the COPY.  See
src/backend/access/transam/README section "Skipping WAL for New
RelFileNode" for the new coding rules.  Maintainers of table access
methods should examine that section.

To maintain data durability, just before commit, we choose between an
fsync of the relfilenode and copying its contents to WAL.  A new GUC,
wal_skip_threshold, guides that choice.  If this change slows a workload
that creates small, permanent relfilenodes under wal_level=minimal, try
adjusting wal_skip_threshold.  Users setting a timeout on COMMIT may
need to adjust that timeout, and log_min_duration_statement analysis
will reflect time consumption moving to COMMIT from commands like COPY.

Internally, this requires a reliable determination of whether
RollbackAndReleaseCurrentSubTransaction() would unlink a relation's
current relfilenode.  Introduce rd_firstRelfilenodeSubid.  Amend the
specification of rd_createSubid such that the field is zero when a new
rel has an old rd_node.  Make relcache.c retain entries for certain
dropped relations until end of transaction.

Bump XLOG_PAGE_MAGIC, since this introduces XLOG_GIST_ASSIGN_LSN.
Future servers accept older WAL, so this bump is discretionary.

Kyotaro Horiguchi, reviewed (in earlier, similar versions) by Robert
Haas.  Heikki Linnakangas and Michael Paquier implemented earlier
designs that materially clarified the problem.  Reviewed, in earlier
designs, by Andrew Dunstan, Andres Freund, Alvaro Herrera, Tom Lane,
Fujii Masao, and Simon Riggs.  Reported by Martijn van Oosterhout.

Discussion: https://postgr.es/m/20150702220524.GA9392@svana.org
This commit is contained in:
Noah Misch
2020-04-04 12:25:34 -07:00
parent 552fcebff0
commit c6b92041d3
53 changed files with 1566 additions and 372 deletions
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26
src/backend/commands/tablecmds.c
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@ -5041,19 +5041,14 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode)
newrel = NULL;
/*
* Prepare a BulkInsertState and options for table_tuple_insert. Because
* we're building a new heap, we can skip WAL-logging and fsync it to disk
* at the end instead (unless WAL-logging is required for archiving or
* streaming replication). The FSM is empty too, so don't bother using it.
* Prepare a BulkInsertState and options for table_tuple_insert. The FSM
* is empty, so don't bother using it.
*/
if (newrel)
{
mycid = GetCurrentCommandId(true);
bistate = GetBulkInsertState();
ti_options = TABLE_INSERT_SKIP_FSM;
if (!XLogIsNeeded())
ti_options |= TABLE_INSERT_SKIP_WAL;
}
else
{
@ -7721,14 +7716,19 @@ ATExecAddIndex(AlteredTableInfo *tab, Relation rel,
/*
* If TryReuseIndex() stashed a relfilenode for us, we used it for the new
* index instead of building from scratch. The DROP of the old edition of
* this index will have scheduled the storage for deletion at commit, so
* cancel that pending deletion.
* index instead of building from scratch. Restore associated fields.
* This may store InvalidSubTransactionId in both fields, in which case
* relcache.c will assume it can rebuild the relcache entry. Hence, do
* this after the CCI that made catalog rows visible to any rebuild. The
* DROP of the old edition of this index will have scheduled the storage
* for deletion at commit, so cancel that pending deletion.
*/
if (OidIsValid(stmt->oldNode))
{
Relation irel = index_open(address.objectId, NoLock);
irel->rd_createSubid = stmt->oldCreateSubid;
irel->rd_firstRelfilenodeSubid = stmt->oldFirstRelfilenodeSubid;
RelationPreserveStorage(irel->rd_node, true);
index_close(irel, NoLock);
}
@ -12054,7 +12054,11 @@ TryReuseIndex(Oid oldId, IndexStmt *stmt)
/* If it's a partitioned index, there is no storage to share. */
if (irel->rd_rel->relkind != RELKIND_PARTITIONED_INDEX)
{
stmt->oldNode = irel->rd_node.relNode;
stmt->oldCreateSubid = irel->rd_createSubid;
stmt->oldFirstRelfilenodeSubid = irel->rd_firstRelfilenodeSubid;
}
index_close(irel, NoLock);
}
}
@ -12990,6 +12994,8 @@ ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode)
table_close(pg_class, RowExclusiveLock);
RelationAssumeNewRelfilenode(rel);
relation_close(rel, NoLock);
/* Make sure the reltablespace change is visible */