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Code review for auto-tuned effective_cache_size.

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Fix integer overflow issue noted by Magnus Hagander, as well as a bunch
of other infelicities in commit ee1e5662d8
and its unreasonably large number of followups.
This commit is contained in:
Tom Lane
2014-01-27 00:05:49 -05:00
parent dd515d4082
commit 2850896961
7 changed files with 78 additions and 68 deletions
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106
src/backend/optimizer/path/costsize.c
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@ -71,6 +71,7 @@
#ifdef _MSC_VER
#include <float.h> /* for _isnan */
#endif
#include <limits.h>
#include <math.h>
#include "access/htup_details.h"
@ -96,13 +97,14 @@
#define LOG2(x) (log(x) / 0.693147180559945)
double seq_page_cost = DEFAULT_SEQ_PAGE_COST;
double random_page_cost = DEFAULT_RANDOM_PAGE_COST;
double cpu_tuple_cost = DEFAULT_CPU_TUPLE_COST;
double cpu_index_tuple_cost = DEFAULT_CPU_INDEX_TUPLE_COST;
double cpu_operator_cost = DEFAULT_CPU_OPERATOR_COST;
int effective_cache_size = -1;
int effective_cache_size = -1; /* will get replaced */
Cost disable_cost = 1.0e10;
@ -456,52 +458,6 @@ cost_index(IndexPath *path, PlannerInfo *root, double loop_count)
path->path.total_cost = startup_cost + run_cost;
}
void
set_default_effective_cache_size(void)
{
/*
* If the value of effective_cache_size is -1, use the preferred
* auto-tune value.
*/
if (effective_cache_size == -1)
{
char buf[32];
snprintf(buf, sizeof(buf), "%d", NBuffers * DEFAULT_EFFECTIVE_CACHE_SIZE_MULTI);
SetConfigOption("effective_cache_size", buf, PGC_POSTMASTER, PGC_S_OVERRIDE);
}
Assert(effective_cache_size > 0);
}
/*
* GUC check_hook for effective_cache_size
*/
bool
check_effective_cache_size(int *newval, void **extra, GucSource source)
{
/*
* -1 indicates a request for auto-tune.
*/
if (*newval == -1)
{
/*
* If we haven't yet changed the boot_val default of -1, just let it
* be. We'll fix it later.
*/
if (effective_cache_size == -1)
return true;
/* Otherwise, substitute the auto-tune value */
*newval = NBuffers * DEFAULT_EFFECTIVE_CACHE_SIZE_MULTI;
}
/* set minimum? */
if (*newval < 1)
*newval = 1;
return true;
}
/*
* index_pages_fetched
* Estimate the number of pages actually fetched after accounting for
@ -4137,3 +4093,59 @@ page_size(double tuples, int width)
{
return ceil(relation_byte_size(tuples, width) / BLCKSZ);
}
/*
* GUC check_hook for effective_cache_size
*/
bool
check_effective_cache_size(int *newval, void **extra, GucSource source)
{
/*
* -1 is the documented way of requesting auto-tune, but we also treat
* zero as meaning that, since we don't consider zero a valid setting.
*/
if (*newval <= 0)
{
/*
* If we haven't yet changed the initial default of -1, just let it
* be. We'll fix it later on during GUC initialization, when
* set_default_effective_cache_size is called. (If we try to do it
* immediately, we may not be looking at the final value of NBuffers.)
*/
if (effective_cache_size == -1)
return true;
/*
* Otherwise, substitute the auto-tune value, being wary of overflow.
*/
if (NBuffers < INT_MAX / 4)
*newval = NBuffers * 4;
else
*newval = INT_MAX;
}
Assert(*newval > 0);
return true;
}
/*
* initialize effective_cache_size at the end of GUC startup
*/
void
set_default_effective_cache_size(void)
{
/*
* If the value of effective_cache_size is still -1 (or zero), replace it
* with the auto-tune value.
*/
if (effective_cache_size <= 0)
{
/* disable the short-circuit in check_effective_cache_size */
effective_cache_size = 0;
/* and let check_effective_cache_size() compute the setting */
SetConfigOption("effective_cache_size", "-1",
PGC_POSTMASTER, PGC_S_OVERRIDE);
}
Assert(effective_cache_size > 0);
}