Fix briefly showing old progress stats for ANALYZE on inherited tables.

ANALYZE on a table with inheritance children analyzes all the child
tables in a loop. When stepping to next child table, it updated the
child rel ID value in the command progress stats, but did not reset
the 'sample_blks_total' and 'sample_blks_scanned' counters.
acquire_sample_rows() updates 'sample_blks_total' as soon as the scan
starts and 'sample_blks_scanned' after processing the first block, but
until then, pg_stat_progress_analyze would display a bogus combination
of the new child table relid with old counter values from the
previously processed child table. Fix by resetting 'sample_blks_total'
and 'sample_blks_scanned' to zero at the same time that
'current_child_table_relid' is updated.

Backpatch to v13, where pg_stat_progress_analyze view was introduced.

Reported-by: Justin Pryzby
Discussion: https://www.postgresql.org/message-id/20230122162345.GP13860%40telsasoft.com

diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index bfd981aa3f370fcd70c5eea3ed144caf52154175..206d1689ef98e7196c11ac2fa5e512577f8aecc7 100644 (file)
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -1531,8 +1531,25 @@ acquire_inherited_sample_rows(Relation onerel, int elevel,
        AcquireSampleRowsFunc acquirefunc = acquirefuncs[i];
        double      childblocks = relblocks[i];
 
-       pgstat_progress_update_param(PROGRESS_ANALYZE_CURRENT_CHILD_TABLE_RELID,
-                                    RelationGetRelid(childrel));
+       /*
+        * Report progress.  The sampling function will normally report blocks
+        * done/total, but we need to reset them to 0 here, so that they don't
+        * show an old value until that.
+        */
+       {
+           const int   progress_index[] = {
+               PROGRESS_ANALYZE_CURRENT_CHILD_TABLE_RELID,
+               PROGRESS_ANALYZE_BLOCKS_DONE,
+               PROGRESS_ANALYZE_BLOCKS_TOTAL
+           };
+           const int64 progress_vals[] = {
+               RelationGetRelid(childrel),
+               0,
+               0,
+           };
+
+           pgstat_progress_update_multi_param(3, progress_index, progress_vals);
+       }
 
        if (childblocks > 0)
        {