assign fss without conditions in estimation of group number

Author: Andrey Kazarinov

cardinality_hooks.c

@@ -453,11 +453,11 @@ aqo_estimate_num_groups(PlannerInfo *root, List *groupExprs,
 	old_ctx_m = MemoryContextSwitchTo(AQOPredictMemCtx);
 
 	predicted = predict_num_groups(root, subpath, groupExprs, &fss);
+	grouped_rel->fss_hash = fss;
 	if (predicted > 0.)
 	{
 		grouped_rel->predicted_cardinality = predicted;
 		grouped_rel->rows = predicted;
-		grouped_rel->fss_hash = fss;
 		MemoryContextSwitchTo(old_ctx_m);
 		MemoryContextReset(AQOPredictMemCtx);
 		return predicted;

t/005_display_groupby_fss.pl

@@ -0,0 +1,79 @@
+use strict;
+use warnings;
+
+use Config;
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+
+use Test::More tests => 2;
+
+my $node = PostgreSQL::Test::Cluster->new('aqotest');
+$node->init;
+$node->append_conf('postgresql.conf', qq{
+						shared_preload_libraries = 'aqo'
+						log_statement = 'ddl'
+						aqo.join_threshold = 0
+						aqo.mode = 'learn'
+						aqo.show_details = 'on'
+						aqo.show_hash = 'on'
+						aqo.min_neighbors_for_predicting = 1
+						enable_nestloop = 'off'
+						enable_mergejoin = 'off'
+						enable_material = 'off'
+					});
+
+$node->start();
+$node->safe_psql('postgres', 'CREATE EXTENSION aqo');
+
+# Create tables with correlated datas in columns
+
+$node->safe_psql('postgres', 'CREATE TABLE a (x1 int, x2 int, x3 int);
+INSERT INTO a (x1, x2, x3) SELECT mod(ival,10), mod(ival,10), mod(ival,10) FROM generate_series(1,1000) As ival');
+
+$node->safe_psql('postgres', 'CREATE TABLE b (y1 int, y2 int, y3 int);
+INSERT INTO b (y1, y2, y3) SELECT mod(ival + 1,10), mod(ival + 1,10), mod(ival + 1,10) FROM generate_series(1,1000) As ival');
+
+my $result;
+
+my $plan = $node->safe_psql('postgres', 'EXPLAIN (analyze true, verbose true)
+SELECT a.x1, b.y1, COUNT(*) FROM a, b WHERE a.x2 = b.y2 GROUP BY a.x1, b.y1;');
+my @fss = $plan =~ /fss=(-?\d+)/g;
+
+$result = $node->safe_psql('postgres', 'SELECT count(*) FROM aqo_data;');
+is($result, 4);
+
+$result = $node->safe_psql('postgres', 'SELECT fss FROM aqo_data;');
+
+my @storage = split(/\n/, $result);
+
+# compare fss from plan and fss from storage
+my $test2 = 1;
+if (scalar @fss == scalar @storage) {
+	foreach my $numb1 (@fss) {
+		my $found = 0;
+
+		# check fss not zero
+		if ($numb1 == 0) {
+			$test2 = 0;
+			last;
+		}
+
+		foreach my $numb2 (@storage) {
+			if ($numb2 == $numb1) {
+				$found = 1;
+				last;
+			}
+		}
+
+		if (!$found) {
+			$test2 = 0;
+			last;
+		}
+	}
+} else {
+	$test2 = 0;
+}
+
+is($test2, 1);
+
+$node->stop();