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Put back a backwards-compatible version of sampling support functions.

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Commit 83e176ec18 removed the longstanding
support functions for block sampling without any consideration of the
impact this would have on third-party FDWs.  The new API is not notably
more functional for FDWs than the old, so forcing them to change doesn't
seem like a good thing.  We can provide the old API as a wrapper (more
or less) around the new one for a minimal amount of extra code.
This commit is contained in:
Tom Lane
2015-05-18 18:34:37 -04:00
parent f5916bb7b5
commit 4db485e75b
3 changed files with 63 additions and 4 deletions
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16
src/include/utils/sampling.h
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@@ -3,7 +3,7 @@
* sampling.h
* definitions for sampling functions
*
* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/utils/sampling.h
@@ -13,7 +13,8 @@
#ifndef SAMPLING_H
#define SAMPLING_H
#include "storage/bufmgr.h"
#include "storage/block.h" /* for typedef BlockNumber */
/* Random generator for sampling code */
typedef unsigned short SamplerRandomState[3];
@@ -23,6 +24,7 @@ extern void sampler_random_init_state(long seed,
extern double sampler_random_fract(SamplerRandomState randstate);
/* Block sampling methods */
/* Data structure for Algorithm S from Knuth 3.4.2 */
typedef struct
{
@@ -40,7 +42,8 @@ extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
extern bool BlockSampler_HasMore(BlockSampler bs);
extern BlockNumber BlockSampler_Next(BlockSampler bs);
/* Reservoid sampling methods */
/* Reservoir sampling methods */
typedef struct
{
double W;
@@ -52,4 +55,11 @@ typedef ReservoirStateData *ReservoirState;
extern void reservoir_init_selection_state(ReservoirState rs, int n);
extern double reservoir_get_next_S(ReservoirState rs, double t, int n);
/* Old API, still in use by assorted FDWs */
/* For backwards compatibility, these declarations are duplicated in vacuum.h */
extern double anl_random_fract(void);
extern double anl_init_selection_state(int n);
extern double anl_get_next_S(double t, int n, double *stateptr);
#endif /* SAMPLING_H */