Fix O(N^2) behavior in pg_dump for large numbers of owned sequences.

The loop that matched owned sequences to their owning tables required time
proportional to number of owned sequences times number of tables; although
this work was only expended in selective-dump situations, which is probably
why the issue wasn't recognized long since.  Refactor slightly so that we
can perform this work after the index array for findTableByOid has been
set up, reducing the time to O(M log N).

Per gripe from Mike Roest.  Since this is a longstanding performance bug,
backpatch to all supported versions.

diff --git a/src/bin/pg_dump/common.c b/src/bin/pg_dump/common.c
index 7f9860f6b7bbe2eb3f7778434e7123a5d8fddad3..fb2889e9c082772489efd6453ad5597a25406bad 100644 (file)
--- a/src/bin/pg_dump/common.c
+++ b/src/bin/pg_dump/common.c
@@ -122,6 +122,9 @@ getSchemaData(int *numTablesPtr)
        tblinfo = getTables(&numTables);
        tblinfoindex = buildIndexArray(tblinfo, numTables, sizeof(TableInfo));
 
+       /* Do this after we've built tblinfoindex */
+       getOwnedSeqs(tblinfo, numTables);
+
        if (g_verbose)
                write_msg(NULL, "reading user-defined functions\n");
        funinfo = getFuncs(&numFuncs);

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index afd4b184cdf28620e1563ddbf86f680d39c646c3..d4c82bea8be99cc9f446f732a0bfe1a7527287c6 100644 (file)
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -3201,40 +3201,45 @@ getTables(int *numTables)
 
        PQclear(res);
 
+       destroyPQExpBuffer(query);
+       destroyPQExpBuffer(delqry);
+       destroyPQExpBuffer(lockquery);
+
+       return tblinfo;
+}
+
+/*
+ * getOwnedSeqs
+ *       identify owned sequences and mark them as dumpable if owning table is
+ *
+ * We used to do this in getTables(), but it's better to do it after the
+ * index used by findTableByOid() has been set up.
+ */
+void
+getOwnedSeqs(TableInfo tblinfo[], int numTables)
+{
+       int                     i;
+
        /*
         * Force sequences that are "owned" by table columns to be dumped whenever
         * their owning table is being dumped.
         */
-       for (i = 0; i < ntups; i++)
+       for (i = 0; i < numTables; i++)
        {
                TableInfo  *seqinfo = &tblinfo[i];
-               int                     j;
+               TableInfo  *owning_tab;
 
                if (!OidIsValid(seqinfo->owning_tab))
                        continue;                       /* not an owned sequence */
                if (seqinfo->dobj.dump)
                        continue;                       /* no need to search */
-
-               /* can't use findTableByOid yet, unfortunately */
-               for (j = 0; j < ntups; j++)
+               owning_tab = findTableByOid(seqinfo->owning_tab);
+               if (owning_tab && owning_tab->dobj.dump)
                {
-                       if (tblinfo[j].dobj.catId.oid == seqinfo->owning_tab)
-                       {
-                               if (tblinfo[j].dobj.dump)
-                               {
-                                       seqinfo->interesting = true;
-                                       seqinfo->dobj.dump = true;
-                               }
-                               break;
-                       }
+                       seqinfo->interesting = true;
+                       seqinfo->dobj.dump = true;
                }
        }
-
-       destroyPQExpBuffer(query);
-       destroyPQExpBuffer(delqry);
-       destroyPQExpBuffer(lockquery);
-
-       return tblinfo;
 }
 
 /*

diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 2351f30618f1a04e6ed844cd164abde11834c61c..3d213db0744c989cdc3793c159db19b6a1e998dc 100644 (file)
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -477,6 +477,7 @@ extern OpclassInfo *getOpclasses(int *numOpclasses);
 extern OpfamilyInfo *getOpfamilies(int *numOpfamilies);
 extern ConvInfo *getConversions(int *numConversions);
 extern TableInfo *getTables(int *numTables);
+extern void getOwnedSeqs(TableInfo tblinfo[], int numTables);
 extern InhInfo *getInherits(int *numInherits);
 extern void getIndexes(TableInfo tblinfo[], int numTables);
 extern void getConstraints(TableInfo tblinfo[], int numTables);