2015-05-14 22:02:54 -04:00
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/*-------------------------------------------------------------------------
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*
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* sampling.h
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* definitions for sampling functions
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*
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2020-01-01 12:21:45 -05:00
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* Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
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2015-05-14 22:02:54 -04:00
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/utils/sampling.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef SAMPLING_H
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#define SAMPLING_H
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2015-05-18 18:34:37 -04:00
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#include "storage/block.h" /* for typedef BlockNumber */
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2015-05-14 22:02:54 -04:00
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2015-05-15 14:37:10 -04:00
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/* Random generator for sampling code */
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typedef unsigned short SamplerRandomState[3];
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extern void sampler_random_init_state(long seed,
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2019-05-22 13:04:48 -04:00
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SamplerRandomState randstate);
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2015-05-15 14:37:10 -04:00
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extern double sampler_random_fract(SamplerRandomState randstate);
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2015-05-14 22:02:54 -04:00
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/* Block sampling methods */
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2015-05-18 18:34:37 -04:00
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2015-05-14 22:02:54 -04:00
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/* Data structure for Algorithm S from Knuth 3.4.2 */
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typedef struct
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{
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BlockNumber N; /* number of blocks, known in advance */
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int n; /* desired sample size */
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BlockNumber t; /* current block number */
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int m; /* blocks selected so far */
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Phase 2 of pgindent updates.
Change pg_bsd_indent to follow upstream rules for placement of comments
to the right of code, and remove pgindent hack that caused comments
following #endif to not obey the general rule.
Commit e3860ffa4dd0dad0dd9eea4be9cc1412373a8c89 wasn't actually using
the published version of pg_bsd_indent, but a hacked-up version that
tried to minimize the amount of movement of comments to the right of
code. The situation of interest is where such a comment has to be
moved to the right of its default placement at column 33 because there's
code there. BSD indent has always moved right in units of tab stops
in such cases --- but in the previous incarnation, indent was working
in 8-space tab stops, while now it knows we use 4-space tabs. So the
net result is that in about half the cases, such comments are placed
one tab stop left of before. This is better all around: it leaves
more room on the line for comment text, and it means that in such
cases the comment uniformly starts at the next 4-space tab stop after
the code, rather than sometimes one and sometimes two tabs after.
Also, ensure that comments following #endif are indented the same
as comments following other preprocessor commands such as #else.
That inconsistency turns out to have been self-inflicted damage
from a poorly-thought-through post-indent "fixup" in pgindent.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
2017-06-21 15:18:54 -04:00
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SamplerRandomState randstate; /* random generator state */
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2015-05-14 22:02:54 -04:00
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} BlockSamplerData;
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typedef BlockSamplerData *BlockSampler;
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extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
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2019-05-22 13:04:48 -04:00
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int samplesize, long randseed);
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2015-05-14 22:02:54 -04:00
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extern bool BlockSampler_HasMore(BlockSampler bs);
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extern BlockNumber BlockSampler_Next(BlockSampler bs);
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2015-05-18 18:34:37 -04:00
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/* Reservoir sampling methods */
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2015-05-15 14:37:10 -04:00
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typedef struct
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{
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2015-05-23 21:35:49 -04:00
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double W;
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Phase 2 of pgindent updates.
Change pg_bsd_indent to follow upstream rules for placement of comments
to the right of code, and remove pgindent hack that caused comments
following #endif to not obey the general rule.
Commit e3860ffa4dd0dad0dd9eea4be9cc1412373a8c89 wasn't actually using
the published version of pg_bsd_indent, but a hacked-up version that
tried to minimize the amount of movement of comments to the right of
code. The situation of interest is where such a comment has to be
moved to the right of its default placement at column 33 because there's
code there. BSD indent has always moved right in units of tab stops
in such cases --- but in the previous incarnation, indent was working
in 8-space tab stops, while now it knows we use 4-space tabs. So the
net result is that in about half the cases, such comments are placed
one tab stop left of before. This is better all around: it leaves
more room on the line for comment text, and it means that in such
cases the comment uniformly starts at the next 4-space tab stop after
the code, rather than sometimes one and sometimes two tabs after.
Also, ensure that comments following #endif are indented the same
as comments following other preprocessor commands such as #else.
That inconsistency turns out to have been self-inflicted damage
from a poorly-thought-through post-indent "fixup" in pgindent.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
2017-06-21 15:18:54 -04:00
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SamplerRandomState randstate; /* random generator state */
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2015-05-15 14:37:10 -04:00
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} ReservoirStateData;
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2015-05-14 22:02:54 -04:00
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typedef ReservoirStateData *ReservoirState;
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extern void reservoir_init_selection_state(ReservoirState rs, int n);
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extern double reservoir_get_next_S(ReservoirState rs, double t, int n);
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2015-05-18 18:34:37 -04:00
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/* 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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extern double anl_random_fract(void);
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extern double anl_init_selection_state(int n);
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extern double anl_get_next_S(double t, int n, double *stateptr);
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Phase 2 of pgindent updates.
Change pg_bsd_indent to follow upstream rules for placement of comments
to the right of code, and remove pgindent hack that caused comments
following #endif to not obey the general rule.
Commit e3860ffa4dd0dad0dd9eea4be9cc1412373a8c89 wasn't actually using
the published version of pg_bsd_indent, but a hacked-up version that
tried to minimize the amount of movement of comments to the right of
code. The situation of interest is where such a comment has to be
moved to the right of its default placement at column 33 because there's
code there. BSD indent has always moved right in units of tab stops
in such cases --- but in the previous incarnation, indent was working
in 8-space tab stops, while now it knows we use 4-space tabs. So the
net result is that in about half the cases, such comments are placed
one tab stop left of before. This is better all around: it leaves
more room on the line for comment text, and it means that in such
cases the comment uniformly starts at the next 4-space tab stop after
the code, rather than sometimes one and sometimes two tabs after.
Also, ensure that comments following #endif are indented the same
as comments following other preprocessor commands such as #else.
That inconsistency turns out to have been self-inflicted damage
from a poorly-thought-through post-indent "fixup" in pgindent.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
2017-06-21 15:18:54 -04:00
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#endif /* SAMPLING_H */
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