pg_dump: prepare attribute stats query.

Follow precedent in pg_dump for preparing queries to improve
performance. Also, simplify the query by removing unnecessary joins.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reported-by: Andres Freund <andres@anarazel.de>
Co-authored-by: Corey Huinker <corey.huinker@gmail.com>
Co-authored-by: Jeff Davis <pgsql@j-davis.com>
Discussion: https://postgr.es/m/CADkLM=dRMC6t8gp9GVf6y6E_r5EChQjMAAh_vPyih_zMiq0zvA@mail.gmail.com

diff --git a/src/bin/pg_dump/pg_backup.h b/src/bin/pg_dump/pg_backup.h
index 350cf659c410e5242f40f74cf64cf9352a7e2a14..e783cc68d8924cbfcf066294af579eefe616ab51 100644 (file)
--- a/src/bin/pg_dump/pg_backup.h
+++ b/src/bin/pg_dump/pg_backup.h
@@ -72,6 +72,7 @@ enum _dumpPreparedQueries
        PREPQUERY_DUMPOPR,
        PREPQUERY_DUMPRANGETYPE,
        PREPQUERY_DUMPTABLEATTACH,
+       PREPQUERY_GETATTRIBUTESTATS,
        PREPQUERY_GETCOLUMNACLS,
        PREPQUERY_GETDOMAINCONSTRAINTS,
 };

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index a1823914656e2bcbf2d95a6e2b5e3a7e75827b3e..0de6c959bb0f6067ee7b877944a4f44228421104 100644 (file)
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -10415,10 +10415,8 @@ dumpComment(Archive *fout, const char *type,
  * param_name, param_type
  */
 static const char *att_stats_arginfo[][2] = {
-       {"relation", "regclass"},
        {"attname", "name"},
        {"inherited", "boolean"},
-       {"version", "integer"},
        {"null_frac", "float4"},
        {"avg_width", "integer"},
        {"n_distinct", "float4"},
@@ -10434,60 +10432,6 @@ static const char *att_stats_arginfo[][2] = {
        {"range_bounds_histogram", "text"},
 };
 
-/*
- * getAttStatsExportQuery --
- *
- * Generate a query that will fetch all attribute (e.g. pg_statistic)
- * stats for a given relation.
- */
-static void
-getAttStatsExportQuery(PQExpBuffer query, Archive *fout,
-                                          const char *schemaname, const char *relname)
-{
-       resetPQExpBuffer(query);
-       appendPQExpBuffer(query,
-                                         "SELECT c.oid::regclass AS relation, "
-                                         "s.attname,"
-                                         "s.inherited,"
-                                         "'%u'::integer AS version, "
-                                         "s.null_frac,"
-                                         "s.avg_width,"
-                                         "s.n_distinct,"
-                                         "s.most_common_vals,"
-                                         "s.most_common_freqs,"
-                                         "s.histogram_bounds,"
-                                         "s.correlation,"
-                                         "s.most_common_elems,"
-                                         "s.most_common_elem_freqs,"
-                                         "s.elem_count_histogram,",
-                                         fout->remoteVersion);
-
-       if (fout->remoteVersion >= 170000)
-               appendPQExpBufferStr(query,
-                                                        "s.range_length_histogram,"
-                                                        "s.range_empty_frac,"
-                                                        "s.range_bounds_histogram ");
-       else
-               appendPQExpBufferStr(query,
-                                                        "NULL AS range_length_histogram,"
-                                                        "NULL AS range_empty_frac,"
-                                                        "NULL AS range_bounds_histogram ");
-
-       appendPQExpBufferStr(query,
-                                                "FROM pg_stats s "
-                                                "JOIN pg_namespace n "
-                                                "ON n.nspname = s.schemaname "
-                                                "JOIN pg_class c "
-                                                "ON c.relname = s.tablename "
-                                                "AND c.relnamespace = n.oid "
-                                                "WHERE s.schemaname = ");
-       appendStringLiteralAH(query, schemaname, fout);
-       appendPQExpBufferStr(query, " AND s.tablename = ");
-       appendStringLiteralAH(query, relname, fout);
-       appendPQExpBufferStr(query, " ORDER BY s.attname, s.inherited");
-}
-
-
 /*
  * appendNamedArgument --
  *
@@ -10513,17 +10457,17 @@ appendNamedArgument(PQExpBuffer out, Archive *fout, const char *argname,
  * Append a formatted pg_restore_relation_stats statement.
  */
 static void
-appendRelStatsImport(PQExpBuffer out, Archive *fout, const RelStatsInfo *rsinfo)
+appendRelStatsImport(PQExpBuffer out, Archive *fout, const RelStatsInfo *rsinfo,
+                                        const char *qualified_name)
 {
-       const char *qualname = fmtQualifiedId(rsinfo->dobj.namespace->dobj.name, rsinfo->dobj.name);
        char            reltuples_str[FLOAT_SHORTEST_DECIMAL_LEN];
 
        float_to_shortest_decimal_buf(rsinfo->reltuples, reltuples_str);
 
        appendPQExpBufferStr(out, "SELECT * FROM pg_catalog.pg_restore_relation_stats(\n");
-       appendPQExpBuffer(out, "\t'relation', '%s'::regclass,\n", qualname);
        appendPQExpBuffer(out, "\t'version', '%u'::integer,\n",
                                          fout->remoteVersion);
+       appendPQExpBuffer(out, "\t'relation', '%s'::regclass,\n", qualified_name);
        appendPQExpBuffer(out, "\t'relpages', '%d'::integer,\n", rsinfo->relpages);
        appendPQExpBuffer(out, "\t'reltuples', '%s'::real,\n", reltuples_str);
        appendPQExpBuffer(out, "\t'relallvisible', '%d'::integer\n);\n",
@@ -10536,13 +10480,18 @@ appendRelStatsImport(PQExpBuffer out, Archive *fout, const RelStatsInfo *rsinfo)
  * Append a series of formatted pg_restore_attribute_stats statements.
  */
 static void
-appendAttStatsImport(PQExpBuffer out, Archive *fout, PGresult *res)
+appendAttStatsImport(PQExpBuffer out, Archive *fout, PGresult *res,
+                                        const char *qualified_name)
 {
        for (int rownum = 0; rownum < PQntuples(res); rownum++)
        {
                const char *sep = "";
 
                appendPQExpBufferStr(out, "SELECT * FROM pg_catalog.pg_restore_attribute_stats(\n");
+               appendPQExpBuffer(out, "\t'version', '%u'::integer,\n",
+                                                 fout->remoteVersion);
+               appendPQExpBuffer(out, "\t'relation', '%s'::regclass,\n",
+                                                 qualified_name);
                for (int argno = 0; argno < lengthof(att_stats_arginfo); argno++)
                {
                        const char *argname = att_stats_arginfo[argno][0];
@@ -10607,6 +10556,7 @@ dumpRelationStats(Archive *fout, const RelStatsInfo *rsinfo)
        DumpableObject *dobj = (DumpableObject *) &rsinfo->dobj;
        DumpId     *deps = NULL;
        int                     ndeps = 0;
+       const char *qualified_name;
 
        /* nothing to do if we are not dumping statistics */
        if (!fout->dopt->dumpStatistics)
@@ -10622,15 +10572,56 @@ dumpRelationStats(Archive *fout, const RelStatsInfo *rsinfo)
        tag = createPQExpBuffer();
        appendPQExpBufferStr(tag, fmtId(dobj->name));
 
-       out = createPQExpBuffer();
+       query = createPQExpBuffer();
+       if (!fout->is_prepared[PREPQUERY_GETATTRIBUTESTATS])
+       {
+               appendPQExpBufferStr(query,
+                                                        "PREPARE getAttributeStats(pg_catalog.name, pg_catalog.name) AS\n"
+                                                        "SELECT s.attname, s.inherited, "
+                                                        "s.null_frac, s.avg_width, s.n_distinct, "
+                                                        "s.most_common_vals, s.most_common_freqs, "
+                                                        "s.histogram_bounds, s.correlation, "
+                                                        "s.most_common_elems, s.most_common_elem_freqs, "
+                                                        "s.elem_count_histogram, ");
+
+               if (fout->remoteVersion >= 170000)
+                       appendPQExpBufferStr(query,
+                                                                "s.range_length_histogram, s.range_empty_frac, "
+                                                                "s.range_bounds_histogram ");
+               else
+                       appendPQExpBufferStr(query,
+                                                                "NULL AS range_length_histogram,"
+                                                                "NULL AS range_empty_frac,"
+                                                                "NULL AS range_bounds_histogram ");
 
-       appendRelStatsImport(out, fout, rsinfo);
+               appendPQExpBufferStr(query,
+                                                        "FROM pg_stats s "
+                                                        "WHERE s.schemaname = $1 "
+                                                        "AND s.tablename = $2 "
+                                                        "ORDER BY s.attname, s.inherited");
+
+               ExecuteSqlStatement(fout, query->data);
+
+               fout->is_prepared[PREPQUERY_GETATTRIBUTESTATS] = true;
+               resetPQExpBuffer(query);
+       }
+
+       appendPQExpBufferStr(query, "EXECUTE getAttributeStats(");
+       appendStringLiteralAH(query, dobj->namespace->dobj.name, fout);
+       appendPQExpBufferStr(query, ", ");
+       appendStringLiteralAH(query, dobj->name, fout);
+       appendPQExpBufferStr(query, "); ");
 
-       query = createPQExpBuffer();
-       getAttStatsExportQuery(query, fout, dobj->namespace->dobj.name,
-                                                  dobj->name);
        res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
-       appendAttStatsImport(out, fout, res);
+
+       out = createPQExpBuffer();
+
+       qualified_name = fmtQualifiedId(rsinfo->dobj.namespace->dobj.name,
+                                                                       rsinfo->dobj.name);
+
+       appendRelStatsImport(out, fout, rsinfo, qualified_name);
+       appendAttStatsImport(out, fout, res, qualified_name);
+
        PQclear(res);
 
        ArchiveEntry(fout, nilCatalogId, createDumpId(),