Allow SET STATISTICS on expression indexes

Index columns are referenced by ordinal number rather than name, e.g.
CREATE INDEX coord_idx ON measured (x, y, (z + t));
ALTER INDEX coord_idx ALTER COLUMN 3 SET STATISTICS 1000;

Incompatibility note for release notes:
\d+ for indexes now also displays Stats Target

Authors: Alexander Korotkov, with contribution by Adrien NAYRAT
Review: Adrien NAYRAT, Simon Riggs
Wordsmith: Simon Riggs

3 files changed, 44 insertions, 4 deletions

diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index ed03cb9c630..0f364231635 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -94,6 +94,30 @@ SELECT * FROM tmp;
          | 4 | name | text | 4.1 | 4.1 | 2 | ((4.1,4.1),(3.1,3.1)) | Mon May 01 00:30:30 1995 PDT | c | {"Mon May 01 00:30:30 1995 PDT","Mon Aug 24 14:43:07 1992 PDT","Wed Dec 31 16:00:00 1969 PST"} | 314159 | (1,1) | 512 | 1 2 3 4 5 6 7 8 | magnetic disk | (1.1,1.1) | [(4.1,4.1),(3.1,3.1)] | ((0,2),(4.1,4.1),(3.1,3.1)) | (4.1,4.1),(3.1,3.1) | ["Wed Dec 31 16:00:00 1969 PST" "infinity"] | Thu Jan 01 00:00:00 1970 | @ 1 hour 10 secs | {1,2,3,4} | {1,2,3,4} | {1,2,3,4}
 (1 row)
 
+CREATE INDEX tmp_idx ON tmp (a, (d + e), b);
+ALTER INDEX tmp_idx ALTER COLUMN 0 SET STATISTICS 1000;
+ERROR:  column number must be in range from 1 to 32767
+LINE 1: ALTER INDEX tmp_idx ALTER COLUMN 0 SET STATISTICS 1000;
+                                         ^
+ALTER INDEX tmp_idx ALTER COLUMN 1 SET STATISTICS 1000;
+ERROR:  cannot alter statistics on non-expression column "a" of index "tmp_idx"
+HINT:  Alter statistics on table column instead.
+ALTER INDEX tmp_idx ALTER COLUMN 2 SET STATISTICS 1000;
+\d+ tmp_idx
+                     Index "public.tmp_idx"
+ Column |       Type       | Definition | Storage | Stats target 
+--------+------------------+------------+---------+--------------
+ a      | integer          | a          | plain   | 
+ expr   | double precision | (d + e)    | plain   | 1000
+ b      | cstring          | b          | plain   | 
+btree, for table "public.tmp"
+
+ALTER INDEX tmp_idx ALTER COLUMN 3 SET STATISTICS 1000;
+ERROR:  cannot alter statistics on non-expression column "b" of index "tmp_idx"
+HINT:  Alter statistics on table column instead.
+ALTER INDEX tmp_idx ALTER COLUMN 4 SET STATISTICS 1000;
+ERROR:  column number 4 of relation "tmp_idx" does not exist
+ALTER INDEX tmp_idx ALTER COLUMN 2 SET STATISTICS -1;
 DROP TABLE tmp;
 --
 -- rename - check on both non-temp and temp tables
diff --git a/src/test/regress/expected/create_index.out b/src/test/regress/expected/create_index.out
index 064adb4640b..8450f2463e8 100644
--- a/src/test/regress/expected/create_index.out
+++ b/src/test/regress/expected/create_index.out
@@ -2324,10 +2324,10 @@ DROP TABLE array_gin_test;
 CREATE INDEX gin_relopts_test ON array_index_op_test USING gin (i)
   WITH (FASTUPDATE=on, GIN_PENDING_LIST_LIMIT=128);
 \d+ gin_relopts_test
-     Index "public.gin_relopts_test"
- Column |  Type   | Definition | Storage 
---------+---------+------------+---------
- i      | integer | i          | plain
+            Index "public.gin_relopts_test"
+ Column |  Type   | Definition | Storage | Stats target 
+--------+---------+------------+---------+--------------
+ i      | integer | i          | plain   | 
 gin, for table "public.array_index_op_test"
 Options: fastupdate=on, gin_pending_list_limit=128
 
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 9a20dd141a2..e6f6669880b 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -142,6 +142,22 @@ INSERT INTO tmp (a, b, c, d, e, f, g, h, i, j, k, l, m, n, p, q, r, s, t, u,
 
 SELECT * FROM tmp;
 
+CREATE INDEX tmp_idx ON tmp (a, (d + e), b);
+
+ALTER INDEX tmp_idx ALTER COLUMN 0 SET STATISTICS 1000;
+
+ALTER INDEX tmp_idx ALTER COLUMN 1 SET STATISTICS 1000;
+
+ALTER INDEX tmp_idx ALTER COLUMN 2 SET STATISTICS 1000;
+
+\d+ tmp_idx
+
+ALTER INDEX tmp_idx ALTER COLUMN 3 SET STATISTICS 1000;
+
+ALTER INDEX tmp_idx ALTER COLUMN 4 SET STATISTICS 1000;
+
+ALTER INDEX tmp_idx ALTER COLUMN 2 SET STATISTICS -1;
+
 DROP TABLE tmp;