Re: [PATCH] pg_dump: Do not dump statistics for excluded tables

Rian McGuire <rian.mcguire@buildkite.com> writes:
> I've attached a patch against master that addresses a small bug in pg_dump.
> Previously, pg_dump would include CREATE STATISTICS statements for
> tables that were excluded from the dump, causing reload to fail if any
> excluded tables had extended statistics.

I agree that's a bug ...

> The patch skips the creation of the StatsExtInfo if the associated
> table does not have the DUMP_COMPONENT_DEFINITION flag set. This is
> similar to how getPublicationTables behaves if a table is excluded.

... but I don't like the details of this patch (and I'm not too
thrilled with the implementation of getPublicationTables, either).
The style in pg_dump is to put such decisions into separate
policy-setting subroutines.  Also, skipping creation of the
DumpableObject altogether is the wrong thing because it'd prevent
pg_dump from tracing or reasoning about dependencies involving the
stats object, which can be relevant even if the object itself isn't
dumped --- this is why all the other data-collection subroutines
operate as they do.  getPublicationTables can probably get away
with its low-rent approach given that publication membership isn't
represented by pg_depend entries, but it's far from clear that it'll
never be an issue for stats.

So I think it needs to be more like the attached.
(I did use your test case verbatim.)

            regards, tom lane

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 8c0b5486b9..050a831226 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -2046,6 +2046,26 @@ selectDumpablePublicationObject(DumpableObject *dobj, Archive *fout)
         DUMP_COMPONENT_ALL : DUMP_COMPONENT_NONE;
 }

+/*
+ * selectDumpableStatisticsObject: policy-setting subroutine
+ *        Mark an extended statistics object as to be dumped or not
+ *
+ * We dump an extended statistics object if the schema it's in and the table
+ * it's for are being dumped.  (This'll need more thought if statistics
+ * objects ever support cross-table stats.)
+ */
+static void
+selectDumpableStatisticsObject(StatsExtInfo *sobj, Archive *fout)
+{
+    if (checkExtensionMembership(&sobj->dobj, fout))
+        return;                    /* extension membership overrides all else */
+
+    sobj->dobj.dump = sobj->dobj.namespace->dobj.dump_contains;
+    if (sobj->stattable == NULL ||
+        !(sobj->stattable->dobj.dump & DUMP_COMPONENT_DEFINITION))
+        sobj->dobj.dump = DUMP_COMPONENT_NONE;
+}
+
 /*
  * selectDumpableObject: policy-setting subroutine
  *        Mark a generic dumpable object as to be dumped or not
@@ -7291,6 +7311,7 @@ getExtendedStatistics(Archive *fout)
     int            i_stxname;
     int            i_stxnamespace;
     int            i_stxowner;
+    int            i_stxrelid;
     int            i_stattarget;
     int            i;

@@ -7302,11 +7323,11 @@ getExtendedStatistics(Archive *fout)

     if (fout->remoteVersion < 130000)
         appendPQExpBufferStr(query, "SELECT tableoid, oid, stxname, "
-                             "stxnamespace, stxowner, (-1) AS stxstattarget "
+                             "stxnamespace, stxowner, stxrelid, (-1) AS stxstattarget "
                              "FROM pg_catalog.pg_statistic_ext");
     else
         appendPQExpBufferStr(query, "SELECT tableoid, oid, stxname, "
-                             "stxnamespace, stxowner, stxstattarget "
+                             "stxnamespace, stxowner, stxrelid, stxstattarget "
                              "FROM pg_catalog.pg_statistic_ext");

     res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
@@ -7318,6 +7339,7 @@ getExtendedStatistics(Archive *fout)
     i_stxname = PQfnumber(res, "stxname");
     i_stxnamespace = PQfnumber(res, "stxnamespace");
     i_stxowner = PQfnumber(res, "stxowner");
+    i_stxrelid = PQfnumber(res, "stxrelid");
     i_stattarget = PQfnumber(res, "stxstattarget");

     statsextinfo = (StatsExtInfo *) pg_malloc(ntups * sizeof(StatsExtInfo));
@@ -7332,10 +7354,12 @@ getExtendedStatistics(Archive *fout)
         statsextinfo[i].dobj.namespace =
             findNamespace(atooid(PQgetvalue(res, i, i_stxnamespace)));
         statsextinfo[i].rolname = getRoleName(PQgetvalue(res, i, i_stxowner));
+        statsextinfo[i].stattable =
+            findTableByOid(atooid(PQgetvalue(res, i, i_stxrelid)));
         statsextinfo[i].stattarget = atoi(PQgetvalue(res, i, i_stattarget));

         /* Decide whether we want to dump it */
-        selectDumpableObject(&(statsextinfo[i].dobj), fout);
+        selectDumpableStatisticsObject(&(statsextinfo[i]), fout);
     }

     PQclear(res);
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 2fe3cbed9a..673ca5c92d 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -423,7 +423,8 @@ typedef struct _indexAttachInfo
 typedef struct _statsExtInfo
 {
     DumpableObject dobj;
-    const char *rolname;
+    const char *rolname;        /* owner */
+    TableInfo  *stattable;        /* link to table the stats are for */
     int            stattarget;        /* statistics target */
 } StatsExtInfo;

diff --git a/src/bin/pg_dump/t/002_pg_dump.pl b/src/bin/pg_dump/t/002_pg_dump.pl
index eb3ec534b4..a671603cd2 100644
--- a/src/bin/pg_dump/t/002_pg_dump.pl
+++ b/src/bin/pg_dump/t/002_pg_dump.pl
@@ -3742,14 +3742,15 @@ my %tests = (
     'CREATE STATISTICS extended_stats_no_options' => {
         create_order => 97,
         create_sql => 'CREATE STATISTICS dump_test.test_ext_stats_no_options
-                            ON col1, col2 FROM dump_test.test_fifth_table',
+                            ON col1, col2 FROM dump_test.test_table',
         regexp => qr/^
-            \QCREATE STATISTICS dump_test.test_ext_stats_no_options ON col1, col2 FROM dump_test.test_fifth_table;\E
+            \QCREATE STATISTICS dump_test.test_ext_stats_no_options ON col1, col2 FROM dump_test.test_table;\E
             /xms,
         like =>
           { %full_runs, %dump_test_schema_runs, section_post_data => 1, },
         unlike => {
             exclude_dump_test_schema => 1,
+            exclude_test_table => 1,
             only_dump_measurement => 1,
         },
     },