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After further thought about support for gathering stats on functional

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indexes, it seems like we ought to put another layer of indirection
between the compute_stats functions and the actual data storage.  This
would allow us to compute the values on-the-fly, for example.
This commit is contained in:
Tom Lane
2004-02-13 06:39:49 +00:00
parent 1a4652333b
commit 8787bc8ef3
2 changed files with 81 additions and 52 deletions
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32
src/include/commands/vacuum.h
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@@ -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 1.49 2004/02/12 23:41:04 tgl Exp $
* $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.50 2004/02/13 06:39:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -40,18 +40,18 @@
* 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.
* minrows is its request for the minimum number of sample rows to be gathered
* (but note this request might not be honored, eg if there are fewer rows
* than that in the table).
*
* 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
* fetchfunc: a function for accessing the column values from the
* sample rows
* samplerows: the number of sample 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).
* The fetchfunc may be called with rownum running from 0 to samplerows-1.
* It returns a Datum and an isNull flag.
*
* 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
@@ -60,6 +60,11 @@
* be CurrentMemoryContext when compute_stats is called.
*----------
*/
typedef struct VacAttrStats *VacAttrStatsP;
typedef Datum (*AnalyzeAttrFetchFunc) (VacAttrStatsP stats, int rownum,
bool *isNull);
typedef struct VacAttrStats
{
/*
@@ -74,9 +79,10 @@ typedef struct VacAttrStats
* 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);
void (*compute_stats) (VacAttrStatsP stats,
AnalyzeAttrFetchFunc fetchfunc,
int samplerows,
double totalrows);
int minrows; /* Minimum # of rows wanted for stats */
void *extra_data; /* for extra type-specific data */
@@ -100,6 +106,8 @@ typedef struct VacAttrStats
* be looked at by type-specific functions.
*/
int tupattnum; /* attribute number within tuples */
HeapTuple *rows; /* access info for fetch function */
TupleDesc tupDesc;
} VacAttrStats;