From e6d8069522c8bde8239dd1fedfb4984efa4b3a1a Mon Sep 17 00:00:00 2001 From: Fujii Masao Date: Thu, 21 Nov 2019 21:10:37 +0900 Subject: [PATCH] Make DROP DATABASE command generate less WAL records. Previously DROP DATABASE generated as many XLOG_DBASE_DROP WAL records as the number of tablespaces that the database to drop uses. This caused the scans of shared_buffers as many times as the number of the tablespaces during recovery because WAL replay of one XLOG_DBASE_DROP record needs that full scan. This could make the recovery time longer especially when shared_buffers is large. This commit changes DROP DATABASE so that it generates only one XLOG_DBASE_DROP record, and registers the information of all the tablespaces into it. Then, WAL replay of XLOG_DBASE_DROP record needs full scan of shared_buffers only once, and which may improve the recovery performance. Author: Fujii Masao Reviewed-by: Kirk Jamison, Simon Riggs Discussion: https://postgr.es/m/CAHGQGwF8YwNH0ZaL+2wjZPkj+ji9UhC+Z4ScnG97WKtVY5L9iw@mail.gmail.com --- src/backend/access/rmgrdesc/dbasedesc.c | 7 ++- src/backend/commands/dbcommands.c | 73 +++++++++++++++++-------- src/include/commands/dbcommands_xlog.h | 5 +- 3 files changed, 59 insertions(+), 26 deletions(-) diff --git a/src/backend/access/rmgrdesc/dbasedesc.c b/src/backend/access/rmgrdesc/dbasedesc.c index c7d60ce10d6..d08c5758729 100644 --- a/src/backend/access/rmgrdesc/dbasedesc.c +++ b/src/backend/access/rmgrdesc/dbasedesc.c @@ -35,9 +35,12 @@ dbase_desc(StringInfo buf, XLogReaderState *record) else if (info == XLOG_DBASE_DROP) { xl_dbase_drop_rec *xlrec = (xl_dbase_drop_rec *) rec; + int i; - appendStringInfo(buf, "dir %u/%u", - xlrec->tablespace_id, xlrec->db_id); + appendStringInfo(buf, "dir"); + for (i = 0; i < xlrec->ntablespaces; i++) + appendStringInfo(buf, " %u/%u", + xlrec->tablespace_ids[i], xlrec->db_id); } } diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c index 446813f0f0b..a70e75a219e 100644 --- a/src/backend/commands/dbcommands.c +++ b/src/backend/commands/dbcommands.c @@ -1411,10 +1411,11 @@ movedb(const char *dbname, const char *tblspcname) xl_dbase_drop_rec xlrec; xlrec.db_id = db_id; - xlrec.tablespace_id = src_tblspcoid; + xlrec.ntablespaces = 1; XLogBeginInsert(); XLogRegisterData((char *) &xlrec, sizeof(xl_dbase_drop_rec)); + XLogRegisterData((char *) &src_tblspcoid, sizeof(Oid)); (void) XLogInsert(RM_DBASE_ID, XLOG_DBASE_DROP | XLR_SPECIAL_REL_UPDATE); @@ -1946,6 +1947,11 @@ remove_dbtablespaces(Oid db_id) Relation rel; TableScanDesc scan; HeapTuple tuple; + List *ltblspc = NIL; + ListCell *cell; + int ntblspc; + int i; + Oid *tablespace_ids; rel = table_open(TableSpaceRelationId, AccessShareLock); scan = table_beginscan_catalog(rel, 0, NULL); @@ -1974,23 +1980,41 @@ remove_dbtablespaces(Oid db_id) (errmsg("some useless files may be left behind in old database directory \"%s\"", dstpath))); - /* Record the filesystem change in XLOG */ - { - xl_dbase_drop_rec xlrec; - - xlrec.db_id = db_id; - xlrec.tablespace_id = dsttablespace; - - XLogBeginInsert(); - XLogRegisterData((char *) &xlrec, sizeof(xl_dbase_drop_rec)); - - (void) XLogInsert(RM_DBASE_ID, - XLOG_DBASE_DROP | XLR_SPECIAL_REL_UPDATE); - } - + ltblspc = lappend_oid(ltblspc, dsttablespace); pfree(dstpath); } + ntblspc = list_length(ltblspc); + if (ntblspc == 0) + { + table_endscan(scan); + table_close(rel, AccessShareLock); + return; + } + + tablespace_ids = (Oid *) palloc(ntblspc * sizeof(Oid)); + i = 0; + foreach(cell, ltblspc) + tablespace_ids[i++] = lfirst_oid(cell); + + /* Record the filesystem change in XLOG */ + { + xl_dbase_drop_rec xlrec; + + xlrec.db_id = db_id; + xlrec.ntablespaces = ntblspc; + + XLogBeginInsert(); + XLogRegisterData((char *) &xlrec, MinSizeOfDbaseDropRec); + XLogRegisterData((char *) tablespace_ids, ntblspc * sizeof(Oid)); + + (void) XLogInsert(RM_DBASE_ID, + XLOG_DBASE_DROP | XLR_SPECIAL_REL_UPDATE); + } + + list_free(ltblspc); + pfree(tablespace_ids); + table_endscan(scan); table_close(rel, AccessShareLock); } @@ -2197,8 +2221,7 @@ dbase_redo(XLogReaderState *record) { xl_dbase_drop_rec *xlrec = (xl_dbase_drop_rec *) XLogRecGetData(record); char *dst_path; - - dst_path = GetDatabasePath(xlrec->db_id, xlrec->tablespace_id); + int i; if (InHotStandby) { @@ -2228,11 +2251,17 @@ dbase_redo(XLogReaderState *record) /* Clean out the xlog relcache too */ XLogDropDatabase(xlrec->db_id); - /* And remove the physical files */ - if (!rmtree(dst_path, true)) - ereport(WARNING, - (errmsg("some useless files may be left behind in old database directory \"%s\"", - dst_path))); + for (i = 0; i < xlrec->ntablespaces; i++) + { + dst_path = GetDatabasePath(xlrec->db_id, xlrec->tablespace_ids[i]); + + /* And remove the physical files */ + if (!rmtree(dst_path, true)) + ereport(WARNING, + (errmsg("some useless files may be left behind in old database directory \"%s\"", + dst_path))); + pfree(dst_path); + } if (InHotStandby) { diff --git a/src/include/commands/dbcommands_xlog.h b/src/include/commands/dbcommands_xlog.h index 46be8a615ac..4e8a442c89f 100644 --- a/src/include/commands/dbcommands_xlog.h +++ b/src/include/commands/dbcommands_xlog.h @@ -32,10 +32,11 @@ typedef struct xl_dbase_create_rec typedef struct xl_dbase_drop_rec { - /* Records dropping of a single subdirectory incl. contents */ Oid db_id; - Oid tablespace_id; + int ntablespaces; /* number of tablespace IDs */ + Oid tablespace_ids[FLEXIBLE_ARRAY_MEMBER]; } xl_dbase_drop_rec; +#define MinSizeOfDbaseDropRec offsetof(xl_dbase_drop_rec, tablespace_ids) extern void dbase_redo(XLogReaderState *rptr); extern void dbase_desc(StringInfo buf, XLogReaderState *rptr);