diff options
Diffstat (limited to 'src/backend/commands/vacuum.c')
| -rw-r--r-- | src/backend/commands/vacuum.c | 121 |
1 files changed, 48 insertions, 73 deletions
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c index 7f13bae8099..4381369bc03 100644 --- a/src/backend/commands/vacuum.c +++ b/src/backend/commands/vacuum.c @@ -13,7 +13,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.329 2006/05/03 22:45:26 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.330 2006/05/10 23:18:39 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -673,9 +673,10 @@ vacuum_set_xid_limits(VacuumStmt *vacstmt, bool sharedRel, * doing ANALYZE, but we always update these stats. This routine works * for both index and heap relation entries in pg_class. * - * We violate no-overwrite semantics here by storing new values for the - * statistics columns directly into the pg_class tuple that's already on - * the page. The reason for this is that if we updated these tuples in + * We violate transaction semantics here by overwriting the rel's + * existing pg_class tuple with the new values. This is reasonably + * safe since the new values are correct whether or not this transaction + * commits. The reason for this is that if we updated these tuples in * the usual way, vacuuming pg_class itself wouldn't work very well --- * by the time we got done with a vacuum cycle, most of the tuples in * pg_class would've been obsoleted. Of course, this only works for @@ -689,59 +690,57 @@ vac_update_relstats(Oid relid, BlockNumber num_pages, double num_tuples, bool hasindex) { Relation rd; - HeapTupleData rtup; HeapTuple ctup; Form_pg_class pgcform; - Buffer buffer; + bool dirty; - /* - * update number of tuples and number of pages in pg_class - */ rd = heap_open(RelationRelationId, RowExclusiveLock); - ctup = SearchSysCache(RELOID, - ObjectIdGetDatum(relid), - 0, 0, 0); + /* Fetch a copy of the tuple to scribble on */ + ctup = SearchSysCacheCopy(RELOID, + ObjectIdGetDatum(relid), + 0, 0, 0); if (!HeapTupleIsValid(ctup)) elog(ERROR, "pg_class entry for relid %u vanished during vacuuming", relid); + pgcform = (Form_pg_class) GETSTRUCT(ctup); - /* get the buffer cache tuple */ - rtup.t_self = ctup->t_self; - ReleaseSysCache(ctup); - if (!heap_fetch(rd, SnapshotNow, &rtup, &buffer, false, NULL)) - elog(ERROR, "pg_class entry for relid %u vanished during vacuuming", - relid); - - /* ensure no one else does this at the same time */ - LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); - - /* overwrite the existing statistics in the tuple */ - pgcform = (Form_pg_class) GETSTRUCT(&rtup); - pgcform->relpages = (int32) num_pages; - pgcform->reltuples = (float4) num_tuples; - pgcform->relhasindex = hasindex; + /* Apply required updates, if any, to copied tuple */ + dirty = false; + if (pgcform->relpages != (int32) num_pages) + { + pgcform->relpages = (int32) num_pages; + dirty = true; + } + if (pgcform->reltuples != (float4) num_tuples) + { + pgcform->reltuples = (float4) num_tuples; + dirty = true; + } + if (pgcform->relhasindex != hasindex) + { + pgcform->relhasindex = hasindex; + dirty = true; + } /* * If we have discovered that there are no indexes, then there's no * primary key either. This could be done more thoroughly... */ if (!hasindex) - pgcform->relhaspkey = false; - - MarkBufferDirty(buffer); - - LockBuffer(buffer, BUFFER_LOCK_UNLOCK); + { + if (pgcform->relhaspkey) + { + pgcform->relhaspkey = false; + dirty = true; + } + } /* - * Invalidate the tuple in the catcaches; this also arranges to flush the - * relation's relcache entry. (If we fail to commit for some reason, no - * flush will occur, but no great harm is done since there are no - * noncritical state updates here.) + * If anything changed, write out the tuple */ - CacheInvalidateHeapTuple(rd, &rtup); - - ReleaseBuffer(buffer); + if (dirty) + heap_inplace_update(rd, ctup); heap_close(rd, RowExclusiveLock); } @@ -753,10 +752,11 @@ vac_update_relstats(Oid relid, BlockNumber num_pages, double num_tuples, * Update the whole-database statistics that are kept in its pg_database * row, and the flat-file copy of pg_database. * - * We violate no-overwrite semantics here by storing new values for the - * statistics columns directly into the tuple that's already on the page. - * As with vac_update_relstats, this avoids leaving dead tuples behind - * after a VACUUM. + * We violate transaction semantics here by overwriting the database's + * existing pg_database tuple with the new values. This is reasonably + * safe since the new values are correct whether or not this transaction + * commits. As with vac_update_relstats, this avoids leaving dead tuples + * behind after a VACUUM. * * This routine is shared by full and lazy VACUUM. Note that it is only * applied after a database-wide VACUUM operation. @@ -767,49 +767,24 @@ vac_update_dbstats(Oid dbid, TransactionId frozenXID) { Relation relation; - ScanKeyData entry[1]; - SysScanDesc scan; HeapTuple tuple; - Buffer buf; Form_pg_database dbform; relation = heap_open(DatabaseRelationId, RowExclusiveLock); - ScanKeyInit(&entry[0], - ObjectIdAttributeNumber, - BTEqualStrategyNumber, F_OIDEQ, - ObjectIdGetDatum(dbid)); - - scan = systable_beginscan(relation, DatabaseOidIndexId, true, - SnapshotNow, 1, entry); - - tuple = systable_getnext(scan); - + /* Fetch a copy of the tuple to scribble on */ + tuple = SearchSysCacheCopy(DATABASEOID, + ObjectIdGetDatum(dbid), + 0, 0, 0); if (!HeapTupleIsValid(tuple)) elog(ERROR, "could not find tuple for database %u", dbid); - - if (scan->irel) - buf = scan->iscan->xs_cbuf; - else - buf = scan->scan->rs_cbuf; - - /* ensure no one else does this at the same time */ - LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE); - dbform = (Form_pg_database) GETSTRUCT(tuple); /* overwrite the existing statistics in the tuple */ dbform->datvacuumxid = vacuumXID; dbform->datfrozenxid = frozenXID; - MarkBufferDirty(buf); - - LockBuffer(buf, BUFFER_LOCK_UNLOCK); - - /* invalidate the tuple in the cache so we'll see the change in cache */ - CacheInvalidateHeapTuple(relation, tuple); - - systable_endscan(scan); + heap_inplace_update(relation, tuple); heap_close(relation, RowExclusiveLock); |