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Commit4db485e

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Put back a backwards-compatible version of sampling support functions.
Commit83e176e removed the longstandingsupport functions for block sampling without any consideration of theimpact this would have on third-party FDWs. The new API is not notablymore functional for FDWs than the old, so forcing them to change doesn'tseem like a good thing. We can provide the old API as a wrapper (moreor less) around the new one for a minimal amount of extra code.
1 parentf5916bb commit4db485e

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3 files changed

+63
-4
lines changed

3 files changed

+63
-4
lines changed

‎src/backend/utils/misc/sampling.c

Lines changed: 45 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
* sampling.c
44
* Relation block sampling routines.
55
*
6-
* Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
6+
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
77
* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
@@ -239,3 +239,47 @@ sampler_random_fract(SamplerRandomState randstate)
239239
{
240240
returnpg_erand48(randstate);
241241
}
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/*
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* Backwards-compatible API for block sampling
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*
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* This code is now deprecated, but since it's still in use by many FDWs,
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* we should keep it for awhile at least. The functionality is the same as
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* sampler_random_fract/reservoir_init_selection_state/reservoir_get_next_S,
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* except that a common random state is used across all callers.
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*/
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staticReservoirStateDataoldrs;
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double
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anl_random_fract(void)
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{
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/* initialize if first time through */
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if (oldrs.randstate[0]==0)
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sampler_random_init_state(random(),oldrs.randstate);
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/* and compute a random fraction */
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returnsampler_random_fract(oldrs.randstate);
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}
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double
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anl_init_selection_state(intn)
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{
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/* initialize if first time through */
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if (oldrs.randstate[0]==0)
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sampler_random_init_state(random(),oldrs.randstate);
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/* Initial value of W (for use when Algorithm Z is first applied) */
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returnexp(-log(sampler_random_fract(oldrs.randstate)) /n);
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}
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double
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anl_get_next_S(doublet,intn,double*stateptr)
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{
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doubleresult;
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oldrs.W=*stateptr;
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result=reservoir_get_next_S(&oldrs,t,n);
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*stateptr=oldrs.W;
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returnresult;
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}

‎src/include/commands/vacuum.h

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -198,4 +198,9 @@ extern void analyze_rel(Oid relid, RangeVar *relation, int options,
198198
BufferAccessStrategybstrategy);
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externboolstd_typanalyze(VacAttrStats*stats);
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/* in utils/misc/sampling.c --- duplicate of declarations in utils/sampling.h */
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externdoubleanl_random_fract(void);
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externdoubleanl_init_selection_state(intn);
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externdoubleanl_get_next_S(doublet,intn,double*stateptr);
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201206
#endif/* VACUUM_H */

‎src/include/utils/sampling.h

Lines changed: 13 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
* sampling.h
44
* definitions for sampling functions
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*
6-
* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
6+
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
77
* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/utils/sampling.h
@@ -13,7 +13,8 @@
1313
#ifndefSAMPLING_H
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#defineSAMPLING_H
1515

16-
#include"storage/bufmgr.h"
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#include"storage/block.h"/* for typedef BlockNumber */
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1718

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/* Random generator for sampling code */
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typedefunsigned shortSamplerRandomState[3];
@@ -23,6 +24,7 @@ extern void sampler_random_init_state(long seed,
2324
externdoublesampler_random_fract(SamplerRandomStaterandstate);
2425

2526
/* Block sampling methods */
27+
2628
/* Data structure for Algorithm S from Knuth 3.4.2 */
2729
typedefstruct
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{
@@ -40,7 +42,8 @@ extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
4042
externboolBlockSampler_HasMore(BlockSamplerbs);
4143
externBlockNumberBlockSampler_Next(BlockSamplerbs);
4244

43-
/* Reservoid sampling methods */
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/* Reservoir sampling methods */
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4447
typedefstruct
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{
4649
doubleW;
@@ -52,4 +55,11 @@ typedef ReservoirStateData *ReservoirState;
5255
externvoidreservoir_init_selection_state(ReservoirStaters,intn);
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externdoublereservoir_get_next_S(ReservoirStaters,doublet,intn);
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58+
/* Old API, still in use by assorted FDWs */
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/* For backwards compatibility, these declarations are duplicated in vacuum.h */
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externdoubleanl_random_fract(void);
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externdoubleanl_init_selection_state(intn);
63+
externdoubleanl_get_next_S(doublet,intn,double*stateptr);
64+
5565
#endif/* SAMPLING_H */

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