114 lines
2.3 KiB
C
114 lines
2.3 KiB
C
/*-------------------------------------------------------------------------
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*
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* misc.c
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*
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*
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* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.21 2001/01/24 19:43:14 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include <sys/types.h>
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#include <sys/file.h>
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#include <time.h>
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#include "postgres.h"
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#include "utils/builtins.h"
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/*
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* Check if data is Null
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*/
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Datum
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nullvalue(PG_FUNCTION_ARGS)
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{
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if (PG_ARGISNULL(0))
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PG_RETURN_BOOL(true);
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PG_RETURN_BOOL(false);
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}
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/*
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* Check if data is not Null
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*/
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Datum
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nonnullvalue(PG_FUNCTION_ARGS)
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{
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if (PG_ARGISNULL(0))
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PG_RETURN_BOOL(false);
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PG_RETURN_BOOL(true);
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}
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/*
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* oidrand (oid o, int4 X)-
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* Takes in an oid and a int4 X, and will return 'true' about 1/X of
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* the time. If X == 0, this will always return true.
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* Useful for doing random sampling or subsetting.
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*
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* Example use:
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* select * from TEMP where oidrand(TEMP.oid, 10)
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* will return about 1/10 of the tuples in TEMP
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*
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* NOTE: the OID input is not used at all. It is there just because of
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* an old optimizer bug: a qual expression containing no variables was
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* mistakenly assumed to be a constant. Pretending to access the row's OID
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* prevented the optimizer from treating the oidrand() result as constant.
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*/
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static bool random_initialized = false;
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Datum
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oidrand(PG_FUNCTION_ARGS)
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{
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#ifdef NOT_USED
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Oid o = PG_GETARG_OID(0);
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#endif
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int32 X = PG_GETARG_INT32(1);
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bool result;
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if (X == 0)
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PG_RETURN_BOOL(true);
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/*
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* We do this because the cancel key is actually a random, so we don't
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* want them to be able to request random numbers using our postmaster
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* seeded value.
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*/
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if (!random_initialized)
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{
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srandom((unsigned int) time(NULL));
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random_initialized = true;
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}
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result = (random() % X == 0);
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PG_RETURN_BOOL(result);
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}
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/*
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oidsrand(int32 X) -
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seeds the random number generator
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always returns true
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*/
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Datum
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oidsrand(PG_FUNCTION_ARGS)
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{
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int32 X = PG_GETARG_INT32(0);
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srandom((unsigned int) X);
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random_initialized = true;
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PG_RETURN_BOOL(true);
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}
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Datum
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userfntest(PG_FUNCTION_ARGS)
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{
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int32 i = PG_GETARG_INT32(0);
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PG_RETURN_INT32(i);
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}
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