diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/utils/cache/lsyscache.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c index 90969744c9d..688740e32da 100644 --- a/src/backend/utils/cache/lsyscache.c +++ b/src/backend/utils/cache/lsyscache.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v 1.39 2000/01/26 05:57:17 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v 1.40 2000/02/16 01:00:23 tgl Exp $ * * NOTES * Eventually, the index information should go through here, too. @@ -183,6 +183,7 @@ double get_attdisbursion(Oid relid, AttrNumber attnum, double min_estimate) { HeapTuple atp; + Form_pg_attribute att_tup; double disbursion; int32 ntuples; @@ -197,10 +198,21 @@ get_attdisbursion(Oid relid, AttrNumber attnum, double min_estimate) relid, attnum); return min_estimate; } + att_tup = (Form_pg_attribute) GETSTRUCT(atp); - disbursion = ((Form_pg_attribute) GETSTRUCT(atp))->attdisbursion; + disbursion = att_tup->attdisbursion; if (disbursion > 0.0) - return disbursion; /* we have a specific estimate */ + return disbursion; /* we have a specific estimate from VACUUM */ + + /* + * Special-case boolean columns: the disbursion of a boolean is highly + * unlikely to be anywhere near 1/numtuples, instead it's probably more + * like 0.5. + * + * Are there any other cases we should wire in special estimates for? + */ + if (att_tup->atttypid == BOOLOID) + return 0.5; /* * Disbursion is either 0 (no data available) or -1 (disbursion |