Convert pre-existing stats_ext tests to new style

The regression tests added in commit 7300a699 test cardinality
estimates using a function that extracts the interesting pieces
from the EXPLAIN output, instead of testing the whole plan. That
seems both easier to understand and less fragile, so this applies
the same approach to pre-existing tests of ndistinct coefficients
and functional dependencies.

Discussion: https://postgr.es/m/dfdac334-9cf2-2597-fb27-f0fb3753f435@2ndquadrant.com

src/test/regress/sql/stats_ext.sql

@@ -3,9 +3,27 @@
 -- We will be checking execution plans without/with statistics, so
 -- let's make sure we get simple non-parallel plans. Also set the
 -- work_mem low so that we can use small amounts of data.
-SET max_parallel_workers = 0;
-SET max_parallel_workers_per_gather = 0;
-SET work_mem = '128kB';
+
+-- check the number of estimated/actual rows in the top node
+create function check_estimated_rows(text) returns table (estimated int, actual int)
+language plpgsql as
+$$
+declare
+    ln text;
+    tmp text[];
+    first_row bool := true;
+begin
+    for ln in
+        execute format('explain analyze %s', $1)
+    loop
+        if first_row then
+            first_row := false;
+            tmp := regexp_match(ln, 'rows=(\d*) .* rows=(\d*)');
+            return query select tmp[1]::int, tmp[2]::int;
+        end if;
+    end loop;
+end;
+$$;
 
 -- Verify failures
 CREATE STATISTICS tst;
@@ -106,25 +124,20 @@ CREATE TABLE ndistinct (
 -- over-estimates when using only per-column statistics
 INSERT INTO ndistinct (a, b, c, filler1)
      SELECT i/100, i/100, i/100, cash_words((i/100)::money)
-       FROM generate_series(1,30000) s(i);
+       FROM generate_series(1,1000) s(i);
 
 ANALYZE ndistinct;
 
 -- Group Aggregate, due to over-estimate of the number of groups
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, b;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY b, c;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY b, c');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c, d;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c, d');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY b, c, d;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY b, c, d');
 
 -- correct command
 CREATE STATISTICS s10 ON a, b, c FROM ndistinct;
@@ -135,22 +148,17 @@ SELECT stxkind, stxndistinct
   FROM pg_statistic_ext WHERE stxrelid = 'ndistinct'::regclass;
 
 -- Hash Aggregate, thanks to estimates improved by the statistic
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, b;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY b, c;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY b, c');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c');
 
 -- last two plans keep using Group Aggregate, because 'd' is not covered
 -- by the statistic and while it's NULL-only we assume 200 values for it
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c, d;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c, d');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY b, c, d;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY b, c, d');
 
 TRUNCATE TABLE ndistinct;
 
@@ -158,50 +166,39 @@ TRUNCATE TABLE ndistinct;
 INSERT INTO ndistinct (a, b, c, filler1)
      SELECT mod(i,50), mod(i,51), mod(i,32),
             cash_words(mod(i,33)::int::money)
-       FROM generate_series(1,10000) s(i);
+       FROM generate_series(1,5000) s(i);
 
 ANALYZE ndistinct;
 
 SELECT stxkind, stxndistinct
   FROM pg_statistic_ext WHERE stxrelid = 'ndistinct'::regclass;
 
--- plans using Group Aggregate, thanks to using correct esimates
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, b;
+-- correct esimates
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c, d;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c, d');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY b, c, d;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY b, c, d');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, d;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, d');
 
 DROP STATISTICS s10;
 
 SELECT stxkind, stxndistinct
   FROM pg_statistic_ext WHERE stxrelid = 'ndistinct'::regclass;
 
--- dropping the statistics switches the plans to Hash Aggregate,
--- due to under-estimates
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, b;
+-- dropping the statistics results in under-estimates
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c, d;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c, d');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY b, c, d;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY b, c, d');
 
-EXPLAIN (COSTS off)
- SELECT COUNT(*) FROM ndistinct GROUP BY a, d;
+SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, d');
 
 -- functional dependencies tests
 CREATE TABLE functional_dependencies (
@@ -214,8 +211,6 @@ CREATE TABLE functional_dependencies (
     d TEXT
 );
 
-SET random_page_cost = 1.2;
-
 CREATE INDEX fdeps_ab_idx ON functional_dependencies (a, b);
 CREATE INDEX fdeps_abc_idx ON functional_dependencies (a, b, c);
 
@@ -225,22 +220,18 @@ INSERT INTO functional_dependencies (a, b, c, filler1)
 
 ANALYZE functional_dependencies;
 
-EXPLAIN (COSTS OFF)
- SELECT * FROM functional_dependencies WHERE a = 1 AND b = '1';
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE a = 1 AND b = ''1''');
 
-EXPLAIN (COSTS OFF)
- SELECT * FROM functional_dependencies WHERE a = 1 AND b = '1' AND c = 1;
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE a = 1 AND b = ''1'' AND c = 1');
 
 -- create statistics
 CREATE STATISTICS func_deps_stat (dependencies) ON a, b, c FROM functional_dependencies;
 
 ANALYZE functional_dependencies;
 
-EXPLAIN (COSTS OFF)
- SELECT * FROM functional_dependencies WHERE a = 1 AND b = '1';
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE a = 1 AND b = ''1''');
 
-EXPLAIN (COSTS OFF)
- SELECT * FROM functional_dependencies WHERE a = 1 AND b = '1' AND c = 1;
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE a = 1 AND b = ''1'' AND c = 1');
 
 -- a => b, a => c, b => c
 TRUNCATE functional_dependencies;
@@ -251,56 +242,27 @@ INSERT INTO functional_dependencies (a, b, c, filler1)
 
 ANALYZE functional_dependencies;
 
-EXPLAIN (COSTS OFF)
- SELECT * FROM functional_dependencies WHERE a = 1 AND b = '1';
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE a = 1 AND b = ''1''');
 
-EXPLAIN (COSTS OFF)
- SELECT * FROM functional_dependencies WHERE a = 1 AND b = '1' AND c = 1;
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE a = 1 AND b = ''1'' AND c = 1');
 
 -- create statistics
 CREATE STATISTICS func_deps_stat (dependencies) ON a, b, c FROM functional_dependencies;
 
 ANALYZE functional_dependencies;
 
-EXPLAIN (COSTS OFF)
- SELECT * FROM functional_dependencies WHERE a = 1 AND b = '1';
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE a = 1 AND b = ''1''');
 
-EXPLAIN (COSTS OFF)
- SELECT * FROM functional_dependencies WHERE a = 1 AND b = '1' AND c = 1;
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE a = 1 AND b = ''1'' AND c = 1');
 
 -- check change of column type doesn't break it
 ALTER TABLE functional_dependencies ALTER COLUMN c TYPE numeric;
 
-EXPLAIN (COSTS OFF)
- SELECT * FROM functional_dependencies WHERE a = 1 AND b = '1' AND c = 1;
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE a = 1 AND b = ''1'' AND c = 1');
 
 ANALYZE functional_dependencies;
 
-EXPLAIN (COSTS OFF)
- SELECT * FROM functional_dependencies WHERE a = 1 AND b = '1' AND c = 1;
-
-RESET random_page_cost;
-
--- check the number of estimated/actual rows in the top node
-create function check_estimated_rows(text) returns table (estimated int, actual int)
-language plpgsql as
-$$
-declare
-    ln text;
-    tmp text[];
-    first_row bool := true;
-begin
-    for ln in
-        execute format('explain analyze %s', $1)
-    loop
-        if first_row then
-            first_row := false;
-            tmp := regexp_match(ln, 'rows=(\d*) .* rows=(\d*)');
-            return query select tmp[1]::int, tmp[2]::int;
-        end if;
-    end loop;
-end;
-$$;
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE a = 1 AND b = ''1'' AND c = 1');
 
 -- MCV lists
 CREATE TABLE mcv_lists (
@@ -419,8 +381,6 @@ ANALYZE mcv_lists;
 SELECT m.* FROM pg_statistic_ext,
               pg_mcv_list_items(stxmcv) m WHERE stxname = 'mcv_lists_stats';
 
-RESET random_page_cost;
-
 -- mcv with arrays
 CREATE TABLE mcv_lists_arrays (
     a TEXT[],