Add hooks for type-specific calculation of ANALYZE statistics. Idea and

coding by Mark Cave-Ayland, some kibitzing by Tom Lane.  initdb forced
due to new column in pg_type.

src/include/commands/vacuum.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.48 2004/02/10 03:42:45 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.49 2004/02/12 23:41:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -23,10 +23,86 @@
 #include "rusagestub.h"
 #endif
 
+#include "access/htup.h"
+#include "catalog/pg_attribute.h"
+#include "catalog/pg_statistic.h"
+#include "catalog/pg_type.h"
 #include "nodes/parsenodes.h"
 #include "utils/rel.h"
 
 
+/*----------
+ * ANALYZE builds one of these structs for each attribute (column) that is
+ * to be analyzed.  The struct and subsidiary data are in anl_context,
+ * so they live until the end of the ANALYZE operation.
+ *
+ * The type-specific typanalyze function is passed a pointer to this struct
+ * and must return TRUE to continue analysis, FALSE to skip analysis of this
+ * column.  In the TRUE case it must set the compute_stats and minrows fields,
+ * and can optionally set extra_data to pass additional info to compute_stats.
+ *
+ * The compute_stats routine will be called after sample rows have been
+ * gathered.  Aside from this struct, it is passed:
+ *		attnum: attribute number within the supplied tuples
+ *		tupDesc: tuple descriptor for the supplied tuples
+ *		totalrows: estimated total number of rows in relation
+ *		rows: an array of the sample tuples
+ *		numrows: the number of sample tuples
+ * Note that the passed attnum and tupDesc could possibly be different from
+ * what one would expect by looking at the pg_attribute row.  It is important
+ * to use these values for extracting attribute values from the given rows
+ * (and not for any other purpose).
+ *
+ * compute_stats should set stats_valid TRUE if it is able to compute
+ * any useful statistics.  If it does, the remainder of the struct holds
+ * the information to be stored in a pg_statistic row for the column.  Be
+ * careful to allocate any pointed-to data in anl_context, which will NOT
+ * be CurrentMemoryContext when compute_stats is called.
+ *----------
+ */
+typedef struct VacAttrStats
+{
+	/*
+	 * These fields are set up by the main ANALYZE code before invoking
+	 * the type-specific typanalyze function.
+	 */
+	Form_pg_attribute attr;		/* copy of pg_attribute row for column */
+	Form_pg_type attrtype;		/* copy of pg_type row for column */
+	MemoryContext anl_context;	/* where to save long-lived data */
+
+	/*
+	 * These fields must be filled in by the typanalyze routine,
+	 * unless it returns FALSE.
+	 */
+	void (*compute_stats) (struct VacAttrStats *stats, int attnum,
+						   TupleDesc tupDesc, double totalrows,
+						   HeapTuple *rows, int numrows);
+	int			minrows;		/* Minimum # of rows wanted for stats */
+	void	   *extra_data;		/* for extra type-specific data */
+
+	/*
+	 * These fields are to be filled in by the compute_stats routine.
+	 * (They are initialized to zero when the struct is created.)
+	 */
+	bool		stats_valid;
+	float4		stanullfrac;	/* fraction of entries that are NULL */
+	int4		stawidth;		/* average width of column values */
+	float4		stadistinct;	/* # distinct values */
+	int2		stakind[STATISTIC_NUM_SLOTS];
+	Oid			staop[STATISTIC_NUM_SLOTS];
+	int			numnumbers[STATISTIC_NUM_SLOTS];
+	float4	   *stanumbers[STATISTIC_NUM_SLOTS];
+	int			numvalues[STATISTIC_NUM_SLOTS];
+	Datum	   *stavalues[STATISTIC_NUM_SLOTS];
+
+	/*
+	 * These fields are private to the main ANALYZE code and should not
+	 * be looked at by type-specific functions.
+	 */
+	int			tupattnum;		/* attribute number within tuples */
+} VacAttrStats;
+
+
 /* State structure for vac_init_rusage/vac_show_rusage */
 typedef struct VacRUsage
 {