Allow pg_stat_statements to track planning statistics.

This commit makes pg_stat_statements support new GUC
pg_stat_statements.track_planning. If this option is enabled,
pg_stat_statements tracks the planning statistics of the statements,
e.g., the number of times the statement was planned, the total time
spent planning the statement, etc. This feature is useful to check
the statements that it takes a long time to plan. Previously since
pg_stat_statements tracked only the execution statistics, we could
not use that for the purpose.

The planning and execution statistics are stored at the end of
each phase separately. So there are not always one-to-one relationship
between them. For example, if the statement is successfully planned
but fails in the execution phase, only its planning statistics are stored.
This may cause the users to be able to see different pg_stat_statements
results from the previous version. To avoid this,
pg_stat_statements.track_planning needs to be disabled.

This commit bumps the version of pg_stat_statements to 1.8
since it changes the definition of pg_stat_statements function.

Author: Julien Rouhaud, Pascal Legrand, Thomas Munro, Fujii Masao
Reviewed-by: Sergei Kornilov, Tomas Vondra, Yoshikazu Imai, Haribabu Kommi, Tom Lane
Discussion: https://postgr.es/m/CAHGQGwFx_=DO-Gu-MfPW3VQ4qC7TfVdH2zHmvZfrGv6fQ3D-Tw@mail.gmail.com
Discussion: https://postgr.es/m/CAEepm=0e59Y_6Q_YXYCTHZkqOc6H2pJ54C_Xe=VFu50Aqqp_sA@mail.gmail.com
Discussion: https://postgr.es/m/DB6PR0301MB21352F6210E3B11934B0DCC790B00@DB6PR0301MB2135.eurprd03.prod.outlook.com

1 files changed, 16 insertions, 0 deletions

diff --git a/contrib/pg_stat_statements/sql/pg_stat_statements.sql b/contrib/pg_stat_statements/sql/pg_stat_statements.sql
index 8b527070d46..435d51008f6 100644
--- a/contrib/pg_stat_statements/sql/pg_stat_statements.sql
+++ b/contrib/pg_stat_statements/sql/pg_stat_statements.sql
@@ -290,4 +290,20 @@ SELECT query, calls, rows FROM pg_stat_statements ORDER BY query COLLATE "C";
 DROP ROLE regress_stats_user1;
 DROP ROLE regress_stats_user2;
 
+--
+-- [re]plan counting
+--
+SELECT pg_stat_statements_reset();
+CREATE TABLE test ();
+PREPARE prep1 AS SELECT COUNT(*) FROM test;
+EXECUTE prep1;
+EXECUTE prep1;
+EXECUTE prep1;
+ALTER TABLE test ADD COLUMN x int;
+EXECUTE prep1;
+SELECT 42;
+SELECT 42;
+SELECT 42;
+SELECT query, plans, calls, rows FROM pg_stat_statements ORDER BY query COLLATE "C";
+
 DROP EXTENSION pg_stat_statements;