Re: BUG #18468: CREATE TABLE ... LIKE leaves orphaned column reference in extended statistics

I wrote:
> We don't know the column mapping there, either.  What we need to have
> our hands on is the "attmap" computed in expandTableLikeClause, and
> then we can pass the stats expressions through map_variable_attnos().

> I think this might not need to be a really large patch, but it
> definitely has to change where generateClonedExtStatsStmt is
> called from.  I can have a go at it if Tomas doesn't want to.

Yeah, this doesn't require a whole lot more than moving the
processing in transformTableLikeClause to expandTableLikeClause.

I chose to get rid of transformExtendedStatistics, because not
only is there nothing for it to do, there will never be any
statements for it to do nothing to.

I plan to sit on this till after the beta1 freeze.

            regards, tom lane

diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
index 639cfa443e..d5c2b2ff0b 100644
--- a/src/backend/parser/parse_utilcmd.c
+++ b/src/backend/parser/parse_utilcmd.c
@@ -87,7 +87,6 @@ typedef struct
     List       *fkconstraints;    /* FOREIGN KEY constraints */
     List       *ixconstraints;    /* index-creating constraints */
     List       *likeclauses;    /* LIKE clauses that need post-processing */
-    List       *extstats;        /* cloned extended statistics */
     List       *blist;            /* "before list" of things to do before
                                  * creating the table */
     List       *alist;            /* "after list" of things to do after creating
@@ -120,13 +119,14 @@ static void transformTableLikeClause(CreateStmtContext *cxt,
 static void transformOfType(CreateStmtContext *cxt,
                             TypeName *ofTypename);
 static CreateStatsStmt *generateClonedExtStatsStmt(RangeVar *heapRel,
-                                                   Oid heapRelid, Oid source_statsid);
+                                                   Oid heapRelid,
+                                                   Oid source_statsid,
+                                                   const AttrMap *attmap);
 static List *get_collation(Oid collation, Oid actual_datatype);
 static List *get_opclass(Oid opclass, Oid actual_datatype);
 static void transformIndexConstraints(CreateStmtContext *cxt);
 static IndexStmt *transformIndexConstraint(Constraint *constraint,
                                            CreateStmtContext *cxt);
-static void transformExtendedStatistics(CreateStmtContext *cxt);
 static void transformFKConstraints(CreateStmtContext *cxt,
                                    bool skipValidation,
                                    bool isAddConstraint);
@@ -246,7 +246,6 @@ transformCreateStmt(CreateStmt *stmt, const char *queryString)
     cxt.fkconstraints = NIL;
     cxt.ixconstraints = NIL;
     cxt.likeclauses = NIL;
-    cxt.extstats = NIL;
     cxt.blist = NIL;
     cxt.alist = NIL;
     cxt.pkey = NULL;
@@ -339,11 +338,6 @@ transformCreateStmt(CreateStmt *stmt, const char *queryString)
      */
     transformCheckConstraints(&cxt, !cxt.isforeign);

-    /*
-     * Postprocess extended statistics.
-     */
-    transformExtendedStatistics(&cxt);
-
     /*
      * Output results.
      */
@@ -1111,61 +1105,25 @@ transformTableLikeClause(CreateStmtContext *cxt, TableLikeClause *table_like_cla
     }

     /*
-     * We cannot yet deal with defaults, CHECK constraints, or indexes, since
-     * we don't yet know what column numbers the copied columns will have in
-     * the finished table.  If any of those options are specified, add the
-     * LIKE clause to cxt->likeclauses so that expandTableLikeClause will be
-     * called after we do know that.  Also, remember the relation OID so that
-     * expandTableLikeClause is certain to open the same table.
+     * We cannot yet deal with defaults, CHECK constraints, indexes, or
+     * statistics, since we don't yet know what column numbers the copied
+     * columns will have in the finished table.  If any of those options are
+     * specified, add the LIKE clause to cxt->likeclauses so that
+     * expandTableLikeClause will be called after we do know that.  Also,
+     * remember the relation OID so that expandTableLikeClause is certain to
+     * open the same table.
      */
     if (table_like_clause->options &
         (CREATE_TABLE_LIKE_DEFAULTS |
          CREATE_TABLE_LIKE_GENERATED |
          CREATE_TABLE_LIKE_CONSTRAINTS |
-         CREATE_TABLE_LIKE_INDEXES))
+         CREATE_TABLE_LIKE_INDEXES |
+         CREATE_TABLE_LIKE_STATISTICS))
     {
         table_like_clause->relationOid = RelationGetRelid(relation);
         cxt->likeclauses = lappend(cxt->likeclauses, table_like_clause);
     }

-    /*
-     * We may copy extended statistics if requested, since the representation
-     * of CreateStatsStmt doesn't depend on column numbers.
-     */
-    if (table_like_clause->options & CREATE_TABLE_LIKE_STATISTICS)
-    {
-        List       *parent_extstats;
-        ListCell   *l;
-
-        parent_extstats = RelationGetStatExtList(relation);
-
-        foreach(l, parent_extstats)
-        {
-            Oid            parent_stat_oid = lfirst_oid(l);
-            CreateStatsStmt *stats_stmt;
-
-            stats_stmt = generateClonedExtStatsStmt(cxt->relation,
-                                                    RelationGetRelid(relation),
-                                                    parent_stat_oid);
-
-            /* Copy comment on statistics object, if requested */
-            if (table_like_clause->options & CREATE_TABLE_LIKE_COMMENTS)
-            {
-                comment = GetComment(parent_stat_oid, StatisticExtRelationId, 0);
-
-                /*
-                 * We make use of CreateStatsStmt's stxcomment option, so as
-                 * not to need to know now what name the statistics will have.
-                 */
-                stats_stmt->stxcomment = comment;
-            }
-
-            cxt->extstats = lappend(cxt->extstats, stats_stmt);
-        }
-
-        list_free(parent_extstats);
-    }
-
     /*
      * Close the parent rel, but keep our AccessShareLock on it until xact
      * commit.  That will prevent someone else from deleting or ALTERing the
@@ -1423,6 +1381,44 @@ expandTableLikeClause(RangeVar *heapRel, TableLikeClause *table_like_clause)
         }
     }

+    /*
+     * Process extended statistics if required.
+     */
+    if (table_like_clause->options & CREATE_TABLE_LIKE_STATISTICS)
+    {
+        List       *parent_extstats;
+        ListCell   *l;
+
+        parent_extstats = RelationGetStatExtList(relation);
+
+        foreach(l, parent_extstats)
+        {
+            Oid            parent_stat_oid = lfirst_oid(l);
+            CreateStatsStmt *stats_stmt;
+
+            stats_stmt = generateClonedExtStatsStmt(heapRel,
+                                                    RelationGetRelid(childrel),
+                                                    parent_stat_oid,
+                                                    attmap);
+
+            /* Copy comment on statistics object, if requested */
+            if (table_like_clause->options & CREATE_TABLE_LIKE_COMMENTS)
+            {
+                comment = GetComment(parent_stat_oid, StatisticExtRelationId, 0);
+
+                /*
+                 * We make use of CreateStatsStmt's stxcomment option, so as
+                 * not to need to know now what name the statistics will have.
+                 */
+                stats_stmt->stxcomment = comment;
+            }
+
+            result = lappend(result, stats_stmt);
+        }
+
+        list_free(parent_extstats);
+    }
+
     /* Done with child rel */
     table_close(childrel, NoLock);

@@ -1837,10 +1833,12 @@ generateClonedIndexStmt(RangeVar *heapRel, Relation source_idx,
  * Generate a CreateStatsStmt node using information from an already existing
  * extended statistic "source_statsid", for the rel identified by heapRel and
  * heapRelid.
+ *
+ * Attribute numbers in expression Vars are adjusted according to attmap.
  */
 static CreateStatsStmt *
 generateClonedExtStatsStmt(RangeVar *heapRel, Oid heapRelid,
-                           Oid source_statsid)
+                           Oid source_statsid, const AttrMap *attmap)
 {
     HeapTuple    ht_stats;
     Form_pg_statistic_ext statsrec;
@@ -1923,10 +1921,19 @@ generateClonedExtStatsStmt(RangeVar *heapRel, Oid heapRelid,

         foreach(lc, exprs)
         {
+            Node       *expr = (Node *) lfirst(lc);
             StatsElem  *selem = makeNode(StatsElem);
+            bool        found_whole_row;
+
+            /* Adjust Vars to match new table's column numbering */
+            expr = map_variable_attnos(expr,
+                                       1, 0,
+                                       attmap,
+                                       InvalidOid,
+                                       &found_whole_row);

             selem->name = NULL;
-            selem->expr = (Node *) lfirst(lc);
+            selem->expr = expr;

             def_names = lappend(def_names, selem);
         }
@@ -2652,19 +2659,6 @@ transformIndexConstraint(Constraint *constraint, CreateStmtContext *cxt)
     return index;
 }

-/*
- * transformExtendedStatistics
- *     Handle extended statistic objects
- *
- * Right now, there's nothing to do here, so we just append the list to
- * the existing "after" list.
- */
-static void
-transformExtendedStatistics(CreateStmtContext *cxt)
-{
-    cxt->alist = list_concat(cxt->alist, cxt->extstats);
-}
-
 /*
  * transformCheckConstraints
  *        handle CHECK constraints
@@ -3457,7 +3451,6 @@ transformAlterTableStmt(Oid relid, AlterTableStmt *stmt,
     cxt.fkconstraints = NIL;
     cxt.ixconstraints = NIL;
     cxt.likeclauses = NIL;
-    cxt.extstats = NIL;
     cxt.blist = NIL;
     cxt.alist = NIL;
     cxt.pkey = NULL;
@@ -3763,9 +3756,6 @@ transformAlterTableStmt(Oid relid, AlterTableStmt *stmt,
         newcmds = lappend(newcmds, newcmd);
     }

-    /* Append extended statistics objects */
-    transformExtendedStatistics(&cxt);
-
     /* Close rel */
     relation_close(rel, NoLock);

diff --git a/src/test/regress/expected/create_table_like.out b/src/test/regress/expected/create_table_like.out
index 0ed94f1d2f..6bfc6d040f 100644
--- a/src/test/regress/expected/create_table_like.out
+++ b/src/test/regress/expected/create_table_like.out
@@ -261,8 +261,23 @@ Check constraints:
 Inherits: test_like_5,
           test_like_5x

+-- Test updating of column numbers in statistics expressions (bug #18468)
+CREATE TABLE test_like_6 (a int, c text, b text);
+CREATE STATISTICS ext_stat ON (a || b) FROM test_like_6;
+ALTER TABLE test_like_6 DROP COLUMN c;
+CREATE TABLE test_like_6c (LIKE test_like_6 INCLUDING ALL);
+\d+ test_like_6c
+                                Table "public.test_like_6c"
+ Column |  Type   | Collation | Nullable | Default | Storage  | Stats target | Description
+--------+---------+-----------+----------+---------+----------+--------------+-------------
+ a      | integer |           |          |         | plain    |              |
+ b      | text    |           |          |         | extended |              |
+Statistics objects:
+    "public.test_like_6c_expr_stat" ON (a || b) FROM test_like_6c
+
 DROP TABLE test_like_4, test_like_4a, test_like_4b, test_like_4c, test_like_4d;
 DROP TABLE test_like_5, test_like_5x, test_like_5c;
+DROP TABLE test_like_6, test_like_6c;
 CREATE TABLE inhg (x text, LIKE inhx INCLUDING INDEXES, y text); /* copies indexes */
 INSERT INTO inhg VALUES (5, 10);
 INSERT INTO inhg VALUES (20, 10); -- should fail
diff --git a/src/test/regress/sql/create_table_like.sql b/src/test/regress/sql/create_table_like.sql
index 4929d373a2..04008a027b 100644
--- a/src/test/regress/sql/create_table_like.sql
+++ b/src/test/regress/sql/create_table_like.sql
@@ -95,8 +95,16 @@ CREATE TABLE test_like_5c (LIKE test_like_4 INCLUDING ALL)
   INHERITS (test_like_5, test_like_5x);
 \d test_like_5c

+-- Test updating of column numbers in statistics expressions (bug #18468)
+CREATE TABLE test_like_6 (a int, c text, b text);
+CREATE STATISTICS ext_stat ON (a || b) FROM test_like_6;
+ALTER TABLE test_like_6 DROP COLUMN c;
+CREATE TABLE test_like_6c (LIKE test_like_6 INCLUDING ALL);
+\d+ test_like_6c
+
 DROP TABLE test_like_4, test_like_4a, test_like_4b, test_like_4c, test_like_4d;
 DROP TABLE test_like_5, test_like_5x, test_like_5c;
+DROP TABLE test_like_6, test_like_6c;

 CREATE TABLE inhg (x text, LIKE inhx INCLUDING INDEXES, y text); /* copies indexes */
 INSERT INTO inhg VALUES (5, 10);