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Fix premature cache release call

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The cache entry for a hypertable is created by calling
ts_hypertable_from_tupleinfo. This sets up the ht->space
structure, which in turn sets up the dimension information.
These structures are allocated in the cache's memory context.
The dimension information is accessed after the cache is
released in ts_subtract_integer_from_now. This PR fixes this
by releasing the cache before returning from the function.

Fixes #4014
This commit is contained in:
gayyappan 2022-01-25 14:23:12 -05:00 committed by gayyappan
parent 64ed2db869
commit 44be03b5c6
3 changed files with 30 additions and 1 deletions
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1
CHANGELOG.md
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@ -19,6 +19,7 @@ accidentally triggering the load of a previous DB version.**
* #3979 Fix deparsing of index predicates
* #4015 Eliminate float rounding instabilities in interpolate
* #4020 Fix ALTER TABLE EventTrigger initialization
* #4024 Fix premature cache release call
**Thanks**
* @erikhh for reporting an issue with time_bucket_gapfill

28
src/hypertable_cache.h
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@ -13,6 +13,34 @@
#include "hypertable.h"
#include "export.h"
/* When a hypertable entry ht is fetched using the cache
* i.e. ts_hypertable_cache_get_entry and variants, all related information such as
* hyperspaces, dimensions etc are also fetched into the cache. These are allocated in
* the cache's memory context.
* If the cache pin is released by calling ts_cache_release or variants, the memory
* associated with hypertable, its space dimensions etc. have also been released.
* As a best practice, call ts_cache_release right before returning from the function
* where the cache entry was acquired. This prevents inadvertent errors if someone
* modifies this function later and uses an indirectly linked object from the cache.
* Example:
* void my_func(...)
* {
*
* Hypertable * ht = ts_hypertable_cache_get_xxx(...)
* ......
*
* if ( error )
* {
* elog(ERROR, ... ); <----- ts_cache_release not needed here.
* }
*
* .....
* ts_cache_release();
* return ..;
* }
* Note that any exceptions/errors i.e. elog/ereport etc. will trigger an automatic
* cache release. So there is no need for additional ts_cache_release() calls.
*/
extern TSDLLEXPORT Hypertable *ts_hypertable_cache_get_entry(Cache *const cache, const Oid relid,
const unsigned int flags);
extern TSDLLEXPORT Hypertable *ts_hypertable_cache_get_cache_and_entry(const Oid relid,

2
src/utils.c
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@ -886,7 +886,6 @@ ts_subtract_integer_from_now(PG_FUNCTION_ARGS)
Cache *hcache;
Hypertable *ht = ts_hypertable_cache_get_cache_and_entry(ht_relid, CACHE_FLAG_NONE, &hcache);
const Dimension *dim = hyperspace_get_open_dimension(ht->space, 0);
ts_cache_release(hcache);
if (!dim)
elog(ERROR, "hypertable has no open partitioning dimension");
@ -901,5 +900,6 @@ ts_subtract_integer_from_now(PG_FUNCTION_ARGS)
elog(ERROR, "could not find valid integer_now function for hypertable");
int64 res = ts_sub_integer_from_now(lag, partitioning_type, now_func);
ts_cache_release(hcache);
return Int64GetDatum(res);
}