Attached patch makes trace_sort control abbreviation debug output for
the text opclass, which makes it consistent with the numeric opclass.
This seems better than relying on someone going to the trouble of
building Postgres themselves to debug cases where abbreviation is the
wrong thing, which we're not 100% sure will not occur. It also allows
wider analysis of where abbreviation helps the most and the least in
production, which is surely a good thing.
I have added this to the next commitfest, but I suggest that it be
quickly committed to the master branch as a maintenance commit.
--
Peter Geoghegan
diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index d874a1a..18cbdd0 100644
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -34,9 +34,6 @@
#include "utils/pg_locale.h"
#include "utils/sortsupport.h"
-#ifdef DEBUG_ABBREV_KEYS
-#define DEBUG_elog_output DEBUG1
-#endif
/* GUC variable */
int bytea_output = BYTEA_OUTPUT_HEX;
@@ -2149,11 +2146,13 @@ bttext_abbrev_abort(int memtupcount, SortSupport ssup)
* time there are differences within full key strings not captured in
* abbreviations.
*/
-#ifdef DEBUG_ABBREV_KEYS
+#ifdef TRACE_SORT
+ if (trace_sort)
{
double norm_abbrev_card = abbrev_distinct / (double) memtupcount;
- elog(DEBUG_elog_output, "abbrev_distinct after %d: %f (key_distinct: %f, norm_abbrev_card: %f, prop_card: %f)",
+ elog(LOG, "bttext_abbrev: abbrev_distinct after %d: %f "
+ "(key_distinct: %f, norm_abbrev_card: %f, prop_card: %f)",
memtupcount, abbrev_distinct, key_distinct, norm_abbrev_card,
tss->prop_card);
}
@@ -2219,11 +2218,11 @@ bttext_abbrev_abort(int memtupcount, SortSupport ssup)
* of moderately high to high abbreviated cardinality. There is little to
* lose but much to gain, which our strategy reflects.
*/
-#ifdef DEBUG_ABBREV_KEYS
- elog(DEBUG_elog_output, "would have aborted abbreviation due to worst-case at %d. abbrev_distinct: %f, key_distinct: %f, prop_card: %f",
- memtupcount, abbrev_distinct, key_distinct, tss->prop_card);
- /* Actually abort only when debugging is disabled */
- return false;
+#ifdef TRACE_SORT
+ if (trace_sort)
+ elog(LOG, "bttext_abbrev: aborted abbreviation at %d "
+ "(abbrev_distinct: %f, key_distinct: %f, prop_card: %f)",
+ memtupcount, abbrev_distinct, key_distinct, tss->prop_card);
#endif
return true;
--
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