Re: Tupple statistics function

> Tatsuo Ishii <t-ishii@sra.co.jp> writes:
> > I have written a small function that show how many tuples are dead
> > etc. in a specified table.
> 
> Dead according to whose viewpoint?  Under MVCC this seems to be
> in the eye of the beholder...
> 
> > Shall I add this function into contrib directory?
> 
> No real objection, but you should carefully document exactly what
> the results mean.
> 
> BTW, I'd suggest accounting for free, reusable space separately from
> "overhead".
> 
>             regards, tom lane

Ok, here are the source code...

/** $Header: /home/t-ishii/repository/pgstattuple/pgstattuple.c,v 1.2 2001/08/30 06:21:48 t-ishii Exp $** Copyright (c)
2001 Tatsuo Ishii** Permission to use, copy, modify, and distribute this software and* its documentation for any
purpose,without fee, and without a* written agreement is hereby granted, provided that the above* copyright notice and
thisparagraph and the following two* paragraphs appear in all copies.*/
 

#include "postgres.h"
#include "fmgr.h"
#include "access/heapam.h"
#include "access/transam.h"

PG_FUNCTION_INFO_V1(pgstattuple);

extern Datum pgstattuple(PG_FUNCTION_ARGS);

/* ----------* pgstattuple:* returns the percentage of dead tuples** C FUNCTION definition* pgstattuple(NAME) returns
FLOAT8*----------*/
 
Datum
pgstattuple(PG_FUNCTION_ARGS)
{   Name    p = PG_GETARG_NAME(0);
   Relation    rel;   HeapScanDesc    scan;   HeapTuple    tuple;   BlockNumber nblocks;   double    table_len;
uint64   tuple_len = 0;   uint64    dead_tuple_len = 0;   uint32    tuple_count = 0;   uint32    dead_tuple_count = 0;
double    tuple_percent;   double    dead_tuple_percent;
 
   rel = heap_openr(NameStr(*p), NoLock);   nblocks = RelationGetNumberOfBlocks(rel);   scan = heap_beginscan(rel,
false,SnapshotAny, 0, NULL);
 
   while ((tuple = heap_getnext(scan,0)))   {if (HeapTupleSatisfiesNow(tuple->t_data)){    tuple_len += tuple->t_len;
tuple_count++;}else{    dead_tuple_len += tuple->t_len;    dead_tuple_count++;}   }   heap_endscan(scan);
heap_close(rel,NoLock);
 
   table_len = (double)nblocks*BLCKSZ;
   if (nblocks == 0)   {tuple_percent = 0.0;dead_tuple_percent = 0.0;   }   else   {tuple_percent =
(double)tuple_len*100.0/table_len;dead_tuple_percent= (double)dead_tuple_len*100.0/table_len;   }
 
   elog(NOTICE,"physical length: %.2fMB live tuples: %u (%.2fMB, %.2f%%) dead tuples: %u (%.2fMB, %.2f%%) overhead:
%.2f%%",
 table_len/1024/1024,
 tuple_count, (double)tuple_len/1024/1024, tuple_percent,
 dead_tuple_count, (double)dead_tuple_len/1024/1024, dead_tuple_percent,
 (nblocks == 0)?0.0: 100.0 - tuple_percent - dead_tuple_percent);
   PG_RETURN_FLOAT8(dead_tuple_percent);
}