Stabilize pg_stat_io writes test

Counting writes only for io_context = 'normal' is unreliable, as backends
using a buffer access strategy could flush all of the dirty buffers out from
under the other backends and checkpointer. Change the test to count writes in
any context. This achieves roughly the same coverage anyway.

Reported-by: Justin Pryzby <pryzby@telsasoft.com>
Author: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://www.postgresql.org/message-id/ZAnWU8WbXEDjrfUE%40telsasoft.com

diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index a668bd2e48151a41357c3a3575b23885d99a38b4..55b4c6df014346d00667f36395fd4c0c62ae10ea 100644 (file)
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -1137,6 +1137,9 @@ SELECT pg_stat_get_subscription_stats(NULL);
 -- extends.
 SELECT sum(extends) AS io_sum_shared_before_extends
   FROM pg_stat_io WHERE io_context = 'normal' AND io_object = 'relation' \gset
+SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
+  FROM pg_stat_io
+  WHERE io_object = 'relation' \gset io_sum_shared_before_
 CREATE TABLE test_io_shared(a int);
 INSERT INTO test_io_shared SELECT i FROM generate_series(1,100)i;
 SELECT pg_stat_force_next_flush();
@@ -1155,15 +1158,12 @@ SELECT :io_sum_shared_after_extends > :io_sum_shared_before_extends;
 
 -- After a checkpoint, there should be some additional IOCONTEXT_NORMAL writes
 -- and fsyncs.
-SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
-  FROM pg_stat_io
-  WHERE io_context = 'normal' AND io_object = 'relation' \gset io_sum_shared_before_
 -- See comment above for rationale for two explicit CHECKPOINTs.
 CHECKPOINT;
 CHECKPOINT;
 SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
   FROM pg_stat_io
-  WHERE io_context = 'normal' AND io_object = 'relation' \gset io_sum_shared_after_
+  WHERE io_object = 'relation' \gset io_sum_shared_after_
 SELECT :io_sum_shared_after_writes > :io_sum_shared_before_writes;
  ?column? 
 ----------

diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 8b946d05cc9f0bc5809a88f0c189ae3711a28662..d958e70a866cbd2b19388f763a69550cdb559fc6 100644 (file)
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -549,6 +549,9 @@ SELECT pg_stat_get_subscription_stats(NULL);
 -- extends.
 SELECT sum(extends) AS io_sum_shared_before_extends
   FROM pg_stat_io WHERE io_context = 'normal' AND io_object = 'relation' \gset
+SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
+  FROM pg_stat_io
+  WHERE io_object = 'relation' \gset io_sum_shared_before_
 CREATE TABLE test_io_shared(a int);
 INSERT INTO test_io_shared SELECT i FROM generate_series(1,100)i;
 SELECT pg_stat_force_next_flush();
@@ -558,16 +561,12 @@ SELECT :io_sum_shared_after_extends > :io_sum_shared_before_extends;
 
 -- After a checkpoint, there should be some additional IOCONTEXT_NORMAL writes
 -- and fsyncs.
-SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
-  FROM pg_stat_io
-  WHERE io_context = 'normal' AND io_object = 'relation' \gset io_sum_shared_before_
 -- See comment above for rationale for two explicit CHECKPOINTs.
 CHECKPOINT;
 CHECKPOINT;
 SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
   FROM pg_stat_io
-  WHERE io_context = 'normal' AND io_object = 'relation' \gset io_sum_shared_after_
-
+  WHERE io_object = 'relation' \gset io_sum_shared_after_
 SELECT :io_sum_shared_after_writes > :io_sum_shared_before_writes;
 SELECT current_setting('fsync') = 'off'
   OR :io_sum_shared_after_fsyncs > :io_sum_shared_before_fsyncs;