Date: Thu, 24 Nov 2005 18:34:03 +1300
From: Mark Kirkwood <markir@paradise.net.nz>
Subject: Re: Hardware/OS recommendations for large databases (
In-reply-to: <BFAA659D.145E5%llonergan@greenplum.com>
To: Luke Lonergan <llonergan@greenplum.com>
Cc: pgsql-performance@postgresql.org,
	"eng@intranet.greenplum.com" <eng@intranet.greenplum.com>
Message-id: <438550CB.5020506@paradise.net.nz>
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References: <BFAA659D.145E5%llonergan@greenplum.com>

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Luke Lonergan wrote:
> Mark,
> 
> This is an excellent idea – unfortunately I’m in Maui right now 
> (Mahalo!) and I’m not getting to testing with this.  My first try was 
> with 8.0.3 and it’s an 8.1 function I presume.
> 
> Not to be lazy – but any hint as to how to do the same thing for 8.0?
> 

Yeah, it's 8.1 - I didn't think to check against 8.0. The attached 
variant works with 8.0.4 (textToQualifiedNameList needs 2 args)

cheers

Mark

P.s. Maui eh, sounds real nice.

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/*
 * fastcount.c
 *
 * Do a count that uses considerably less CPU time than an aggregate.
 *
 * (Variant for 8.0.x - textToQualifiedNameList needs 2 args)
 */

#include "postgres.h"

#include "funcapi.h"
#include "access/heapam.h"
#include "catalog/namespace.h"
#include "utils/builtins.h"


extern Datum fastcount(PG_FUNCTION_ARGS);


PG_FUNCTION_INFO_V1(fastcount);
Datum
fastcount(PG_FUNCTION_ARGS)
{
	text	   *relname = PG_GETARG_TEXT_P(0);
	RangeVar   *relrv;
	Relation	rel;
	HeapScanDesc scan;
	HeapTuple	tuple;
	int64		result = 0;

	/* Use the name to get a suitable range variable and open the relation. */
	relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname, ""));
	rel = heap_openrv(relrv, AccessShareLock);

	/* Start a heap scan on the relation. */
	scan = heap_beginscan(rel, SnapshotNow, 0, NULL);
	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
	{
		result++;
	}

	/* End the scan and close up the relation. */
	heap_endscan(scan);
	heap_close(rel, AccessShareLock);


	PG_RETURN_INT64(result);
}

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