Replace ALTER TABLE ... SET STATISTICS DISTINCT with a more general mechanism.

Attributes can now have options, just as relations and tablespaces do, and
the reloptions code is used to parse, validate, and store them.  For
simplicity and because these options are not performance critical, we store
them in a separate cache rather than the main relcache.

Thanks to Alex Hunsaker for the review.

1 files changed, 27 insertions, 7 deletions

diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 7d4087c915b..f27a6dad2e6 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.147 2010/01/02 16:57:36 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.148 2010/01/22 16:40:18 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -39,6 +39,7 @@
 #include "storage/proc.h"
 #include "storage/procarray.h"
 #include "utils/acl.h"
+#include "utils/attoptcache.h"
 #include "utils/datum.h"
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
@@ -493,6 +494,8 @@ do_analyze_rel(Relation onerel, VacuumStmt *vacstmt,
 		for (i = 0; i < attr_cnt; i++)
 		{
 			VacAttrStats *stats = vacattrstats[i];
+			AttributeOpts *aopt =
+				get_attribute_options(onerel->rd_id, stats->attr->attnum);
 
 			stats->rows = rows;
 			stats->tupDesc = onerel->rd_att;
@@ -501,9 +504,17 @@ do_analyze_rel(Relation onerel, VacuumStmt *vacstmt,
 									 numrows,
 									 totalrows);
 
-			/* If attdistinct is set, override with that value */
-			if (stats->attr->attdistinct != 0)
-				stats->stadistinct = stats->attr->attdistinct;
+			/*
+			 * If the appropriate flavor of the n_distinct option is
+			 * specified, override with the corresponding value.
+			 */
+			if (aopt != NULL)
+			{
+				float8	n_distinct =
+					inh ? aopt->n_distinct_inherited : aopt->n_distinct;
+				if (n_distinct != 0.0)
+					stats->stadistinct = n_distinct;
+			}
 
 			MemoryContextResetAndDeleteChildren(col_context);
 		}
@@ -751,6 +762,9 @@ compute_index_stats(Relation onerel, double totalrows,
 			for (i = 0; i < attr_cnt; i++)
 			{
 				VacAttrStats *stats = thisdata->vacattrstats[i];
+				AttributeOpts *aopt =
+					get_attribute_options(stats->attr->attrelid,
+						stats->attr->attnum);
 
 				stats->exprvals = exprvals + i;
 				stats->exprnulls = exprnulls + i;
@@ -759,9 +773,15 @@ compute_index_stats(Relation onerel, double totalrows,
 										 ind_fetch_func,
 										 numindexrows,
 										 totalindexrows);
-				/* If attdistinct is set, override with that value */
-				if (stats->attr->attdistinct != 0)
-					stats->stadistinct = stats->attr->attdistinct;
+
+				/*
+				 * If the n_distinct option is specified, it overrides the
+				 * above computation.  For indices, we always use just
+				 * n_distinct, not n_distinct_inherited.
+				 */
+				if (aopt != NULL && aopt->n_distinct != 0.0)
+					stats->stadistinct = aopt->n_distinct;
+
 				MemoryContextResetAndDeleteChildren(col_context);
 			}
 		}