database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-09-08 00:47:37 +03:00
Code Activity

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

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

46
src/backend/utils/misc/sampling.c
View File

@@ -3,7 +3,7 @@
* sampling.c
* Relation block sampling routines.
*
* Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
@@ -239,3 +239,47 @@ sampler_random_fract(SamplerRandomState randstate)
{
return pg_erand48(randstate);
}
/*
* Backwards-compatible API for block sampling
*
* This code is now deprecated, but since it's still in use by many FDWs,
* we should keep it for awhile at least. The functionality is the same as
* sampler_random_fract/reservoir_init_selection_state/reservoir_get_next_S,
* except that a common random state is used across all callers.
*/
static ReservoirStateData oldrs;
double
anl_random_fract(void)
{
/* initialize if first time through */
if (oldrs.randstate[0] == 0)
sampler_random_init_state(random(), oldrs.randstate);
/* and compute a random fraction */
return sampler_random_fract(oldrs.randstate);
}
double
anl_init_selection_state(int n)
{
/* initialize if first time through */
if (oldrs.randstate[0] == 0)
sampler_random_init_state(random(), oldrs.randstate);
/* Initial value of W (for use when Algorithm Z is first applied) */
return exp(-log(sampler_random_fract(oldrs.randstate)) / n);
}
double
anl_get_next_S(double t, int n, double *stateptr)
{
double result;
oldrs.W = *stateptr;
result = reservoir_get_next_S(&oldrs, t, n);
*stateptr = oldrs.W;
return result;
}