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Separate block sampling functions

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Refactoring ahead of tablesample patch

Requested and reviewed by Michael Paquier

Petr Jelinek
This commit is contained in:
Simon Riggs
2015-05-15 04:02:54 +02:00
parent 5a3022fde0
commit 83e176ec18
7 changed files with 287 additions and 232 deletions
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10
contrib/postgres_fdw/postgres_fdw.c
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@ -37,6 +37,7 @@
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/sampling.h"
PG_MODULE_MAGIC;
@ -202,7 +203,7 @@ typedef struct PgFdwAnalyzeState
/* for random sampling */
double samplerows; /* # of rows fetched */
double rowstoskip; /* # of rows to skip before next sample */
double rstate; /* random state */
ReservoirStateData rstate; /* state for reservoir sampling*/
/* working memory contexts */
MemoryContext anl_cxt; /* context for per-analyze lifespan data */
@ -2411,7 +2412,7 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel,
astate.numrows = 0;
astate.samplerows = 0;
astate.rowstoskip = -1; /* -1 means not set yet */
astate.rstate = anl_init_selection_state(targrows);
reservoir_init_selection_state(&astate.rstate, targrows);
/* Remember ANALYZE context, and create a per-tuple temp context */
astate.anl_cxt = CurrentMemoryContext;
@ -2551,13 +2552,12 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
* analyze.c; see Jeff Vitter's paper.
*/
if (astate->rowstoskip < 0)
astate->rowstoskip = anl_get_next_S(astate->samplerows, targrows,
&astate->rstate);
astate->rowstoskip = reservoir_get_next_S(&astate->rstate, astate->samplerows, targrows);
if (astate->rowstoskip <= 0)
{
/* Choose a random reservoir element to replace. */
pos = (int) (targrows * anl_random_fract());
pos = (int) (targrows * sampler_random_fract());
Assert(pos >= 0 && pos < targrows);
heap_freetuple(astate->rows[pos]);
}