Give a better error for duplicate entries in VACUUM/ANALYZE column list.

Previously, the code didn't think about this case and would just try to
analyze such a column twice.  That would fail at the point of inserting
the second version of the pg_statistic row, with obscure error messsages
like "duplicate key value violates unique constraint" or "tuple already
updated by self", depending on context and PG version.  We could allow
the case by ignoring duplicate column specifications, but it seems better
to reject it explicitly.

The bogus error messages seem like arguably a bug, so back-patch to
all supported versions.

Nathan Bossart, per a report from Michael Paquier, and whacked
around a bit by me.

Discussion: https://postgr.es/m/E061A8E3-5E3D-494D-94F0-E8A9B312BBFC@amazon.com

diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 08fc18e96b431908ce3b76af2909dda2c3b6fb8b..1248b2ee5c0b76aab19ad05b7072e1345651bcf4 100644 (file)
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -370,10 +370,14 @@ do_analyze_rel(Relation onerel, int options, VacuumParams *params,
        /*
         * Determine which columns to analyze
         *
-        * Note that system attributes are never analyzed.
+        * Note that system attributes are never analyzed, so we just reject them
+        * at the lookup stage.  We also reject duplicate column mentions.  (We
+        * could alternatively ignore duplicates, but analyzing a column twice
+        * won't work; we'd end up making a conflicting update in pg_statistic.)
         */
        if (va_cols != NIL)
        {
+               Bitmapset  *unique_cols = NULL;
                ListCell   *le;
 
                vacattrstats = (VacAttrStats **) palloc(list_length(va_cols) *
@@ -389,6 +393,13 @@ do_analyze_rel(Relation onerel, int options, VacuumParams *params,
                                                (errcode(ERRCODE_UNDEFINED_COLUMN),
                                                 errmsg("column \"%s\" of relation \"%s\" does not exist",
                                                                col, RelationGetRelationName(onerel))));
+                       if (bms_is_member(i, unique_cols))
+                               ereport(ERROR,
+                                               (errcode(ERRCODE_DUPLICATE_COLUMN),
+                                                errmsg("column \"%s\" of relation \"%s\" is specified twice",
+                                                               col, RelationGetRelationName(onerel))));
+                       unique_cols = bms_add_member(unique_cols, i);
+
                        vacattrstats[tcnt] = examine_attribute(onerel, i, NULL);
                        if (vacattrstats[tcnt] != NULL)
                                tcnt++;
@@ -527,9 +538,9 @@ do_analyze_rel(Relation onerel, int options, VacuumParams *params,
                        stats->rows = rows;
                        stats->tupDesc = onerel->rd_att;
                        stats->compute_stats(stats,
-                                                                        std_fetch_func,
-                                                                        numrows,
-                                                                        totalrows);
+                                                                std_fetch_func,
+                                                                numrows,
+                                                                totalrows);
 
                        /*
                         * If the appropriate flavor of the n_distinct option is
@@ -831,9 +842,9 @@ compute_index_stats(Relation onerel, double totalrows,
                                stats->exprnulls = exprnulls + i;
                                stats->rowstride = attr_cnt;
                                stats->compute_stats(stats,
-                                                                                ind_fetch_func,
-                                                                                numindexrows,
-                                                                                totalindexrows);
+                                                                        ind_fetch_func,
+                                                                        numindexrows,
+                                                                        totalindexrows);
 
                                /*
                                 * If the n_distinct option is specified, it overrides the

diff --git a/src/test/regress/expected/vacuum.out b/src/test/regress/expected/vacuum.out
index 6f686630875bc687a0cc87fd6973d02c4f41b306..a16f26da7e7d4d1848fbd5cab075486da302d8ef 100644 (file)
--- a/src/test/regress/expected/vacuum.out
+++ b/src/test/regress/expected/vacuum.out
@@ -90,4 +90,9 @@ UPDATE vacparted SET b = 'b';
 VACUUM (ANALYZE) vacparted;
 VACUUM (FULL) vacparted;
 VACUUM (FREEZE) vacparted;
+-- check behavior with duplicate column mentions
+VACUUM ANALYZE vacparted(a,b,a);
+ERROR:  column "a" of relation "vacparted" is specified twice
+ANALYZE vacparted(a,b,b);
+ERROR:  column "b" of relation "vacparted" is specified twice
 DROP TABLE vacparted;

diff --git a/src/test/regress/sql/vacuum.sql b/src/test/regress/sql/vacuum.sql
index 7c5fb049176bbd12305099e36b96c1a25ed74dd4..96a848ca954b0a0a11f1b323ca75b6aed79e1a77 100644 (file)
--- a/src/test/regress/sql/vacuum.sql
+++ b/src/test/regress/sql/vacuum.sql
@@ -73,4 +73,9 @@ UPDATE vacparted SET b = 'b';
 VACUUM (ANALYZE) vacparted;
 VACUUM (FULL) vacparted;
 VACUUM (FREEZE) vacparted;
+
+-- check behavior with duplicate column mentions
+VACUUM ANALYZE vacparted(a,b,a);
+ANALYZE vacparted(a,b,b);
+
 DROP TABLE vacparted;