Improve the performance of relation deletes during recovery.

When multiple relations are deleted at the same transaction,
the files of those relations are deleted by one call to smgrdounlinkall(),
which leads to scan whole shared_buffers only one time. OTOH,
previously, during recovery, smgrdounlink() (not smgrdounlinkall()) was
called for each file to delete, which led to scan shared_buffers
multiple times. Obviously this could cause to increase the WAL replay
time very much especially when shared_buffers was huge.

To alleviate this situation, this commit changes the recovery so that
it also calls smgrdounlinkall() only one time to delete multiple
relation files.

This is just fix for oversight of commit 279628a0a7, not new feature.
So, per discussion on pgsql-hackers, we concluded to backpatch this
to all supported versions.

Author: Fujii Masao
Reviewed-by: Michael Paquier, Andres Freund, Thomas Munro, Kyotaro Horiguchi, Takayuki Tsunakawa
Discussion: https://postgr.es/m/CAHGQGwHVQkdfDqtvGVkty+19cQakAydXn1etGND3X0PHbZ3+6w@mail.gmail.com

diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index d78ed62ea773d80639356a8e5a85c052a74c7a19..c04baf34039f6c81d480e1d9291a8aae8303aba8 100644 (file)
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1362,7 +1362,6 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
        RelFileNode *delrels;
        int                     ndelrels;
        SharedInvalidationMessage *invalmsgs;
-       int                     i;
 
        /*
         * Validate the GID, and lock the GXACT to ensure that two backends do not
@@ -1452,13 +1451,9 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
                delrels = abortrels;
                ndelrels = hdr->nabortrels;
        }
-       for (i = 0; i < ndelrels; i++)
-       {
-               SMgrRelation srel = smgropen(delrels[i], InvalidBackendId);
 
-               smgrdounlink(srel, false);
-               smgrclose(srel);
-       }
+       /* Make sure files supposed to be dropped are dropped */
+       DropRelationFiles(delrels, ndelrels, false);
 
        /*
         * Handle cache invalidation messages.

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 59cb3aab9f787fb0f15789f389191b2063b90422..fc6000539e75ccaea3c05475eceafee959eacba2 100644 (file)
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -4710,7 +4710,6 @@ xact_redo_commit_internal(TransactionId xid, XLogRecPtr lsn,
                                                  uint32 xinfo)
 {
        TransactionId max_xid;
-       int                     i;
 
        max_xid = TransactionIdLatest(xid, nsubxacts, sub_xids);
 
@@ -4805,16 +4804,8 @@ xact_redo_commit_internal(TransactionId xid, XLogRecPtr lsn,
                 */
                XLogFlush(lsn);
 
-               for (i = 0; i < nrels; i++)
-               {
-                       SMgrRelation srel = smgropen(xnodes[i], InvalidBackendId);
-                       ForkNumber      fork;
-
-                       for (fork = 0; fork <= MAX_FORKNUM; fork++)
-                               XLogDropRelation(xnodes[i], fork);
-                       smgrdounlink(srel, true);
-                       smgrclose(srel);
-               }
+               /* Make sure files supposed to be dropped are dropped */
+               DropRelationFiles(xnodes, nrels, true);
        }
 
        /*
@@ -4886,7 +4877,6 @@ xact_redo_abort(xl_xact_abort *xlrec, TransactionId xid)
 {
        TransactionId *sub_xids;
        TransactionId max_xid;
-       int                     i;
 
        sub_xids = (TransactionId *) &(xlrec->xnodes[xlrec->nrels]);
        max_xid = TransactionIdLatest(xid, xlrec->nsubxacts, sub_xids);
@@ -4945,16 +4935,7 @@ xact_redo_abort(xl_xact_abort *xlrec, TransactionId xid)
        }
 
        /* Make sure files supposed to be dropped are dropped */
-       for (i = 0; i < xlrec->nrels; i++)
-       {
-               SMgrRelation srel = smgropen(xlrec->xnodes[i], InvalidBackendId);
-               ForkNumber      fork;
-
-               for (fork = 0; fork <= MAX_FORKNUM; fork++)
-                       XLogDropRelation(xlrec->xnodes[i], fork);
-               smgrdounlink(srel, true);
-               smgrclose(srel);
-       }
+       DropRelationFiles(xlrec->xnodes, xlrec->nrels, true);
 }
 
 void

diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index 6e7430bac4b8f11fa8755280d7fb6fc684461237..73e11e9a78a73b8dcaa7d4ea984d774045ee3434 100644 (file)
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -26,6 +26,7 @@
 #include <sys/file.h>
 
 #include "miscadmin.h"
+#include "access/xlogutils.h"
 #include "access/xlog.h"
 #include "catalog/catalog.h"
 #include "portability/instr_time.h"
@@ -1625,6 +1626,43 @@ ForgetDatabaseFsyncRequests(Oid dbid)
        }
 }
 
+/*
+ * DropRelationFiles -- drop files of all given relations
+ */
+void
+DropRelationFiles(RelFileNode *delrels, int ndelrels, bool isRedo)
+{
+       SMgrRelation *srels;
+       int                     i;
+
+       srels = palloc(sizeof(SMgrRelation) * ndelrels);
+       for (i = 0; i < ndelrels; i++)
+       {
+               SMgrRelation srel = smgropen(delrels[i], InvalidBackendId);
+
+               if (isRedo)
+               {
+                       ForkNumber      fork;
+
+                       for (fork = 0; fork <= MAX_FORKNUM; fork++)
+                               XLogDropRelation(delrels[i], fork);
+               }
+               srels[i] = srel;
+       }
+
+       smgrdounlinkall(srels, ndelrels, isRedo);
+
+       /*
+        * Call smgrclose() in reverse order as when smgropen() is called.
+        * This trick enables remove_from_unowned_list() in smgrclose()
+        * to search the SMgrRelation from the unowned list,
+        * with O(1) performance.
+        */
+       for (i = ndelrels - 1; i >= 0; i--)
+               smgrclose(srels[i]);
+       pfree(srels);
+}
+
 
 /*
  *     _fdvec_alloc() -- Make a MdfdVec object.

diff --git a/src/include/storage/smgr.h b/src/include/storage/smgr.h
index ba7c909451d9c1b46c6d3f97a7e7b536f758c721..7b27cf5331671f46330b066b0526f57ddf053386 100644 (file)
--- a/src/include/storage/smgr.h
+++ b/src/include/storage/smgr.h
@@ -135,6 +135,7 @@ extern void RememberFsyncRequest(RelFileNode rnode, ForkNumber forknum,
                                         BlockNumber segno);
 extern void ForgetRelationFsyncRequests(RelFileNode rnode, ForkNumber forknum);
 extern void ForgetDatabaseFsyncRequests(Oid dbid);
+extern void DropRelationFiles(RelFileNode *delrels, int ndelrels, bool isRedo);
 
 /* smgrtype.c */
 extern Datum smgrout(PG_FUNCTION_ARGS);