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Optimize check_search_path() by using SearchPathCache.

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A hash lookup is faster than re-validating the string, particularly
because we use SplitIdentifierString() for validation.

Important when search_path changes frequently.

Discussion: https://postgr.es/m/04c8592dbd694e4114a3ed87139a7a04e4363030.camel%40j-davis.com
This commit is contained in:
Jeff Davis 2023-11-20 15:53:42 -08:00
parent 8efa301532
commit ad57c2a7c5
1 changed files with 54 additions and 2 deletions
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56
src/backend/catalog/namespace.c
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@ -235,6 +235,10 @@ static bool MatchNamedCall(HeapTuple proctup, int nargs, List *argnames,
* when a function has search_path set in proconfig. Add a search path cache
* that can be used by recomputeNamespacePath().
*
* The cache is also used to remember already-validated strings in
* check_search_path() to avoid the need to call SplitIdentifierString()
* repeatedly.
*
* The search path cache is based on a wrapper around a simplehash hash table
* (nsphash, defined below). The spcache wrapper deals with OOM while trying
* to initialize a key, and also offers a more convenient API.
@ -296,6 +300,21 @@ spcache_init(void)
searchPathCacheValid = true;
}
/*
* Look up entry in search path cache without inserting. Returns NULL if not
* present.
*/
static SearchPathCacheEntry *
spcache_lookup(const char *searchPath, Oid roleid)
{
SearchPathCacheKey cachekey = {
.searchPath = searchPath,
.roleid = roleid
};
return nsphash_lookup(SearchPathCache, cachekey);
}
/*
* Look up or insert entry in search path cache.
*
@ -4578,11 +4597,40 @@ ResetTempTableNamespace(void)
bool
check_search_path(char **newval, void **extra, GucSource source)
{
Oid roleid = InvalidOid;
const char *searchPath = *newval;
char *rawname;
List *namelist;
bool use_cache = (SearchPathCacheContext != NULL);
/* Need a modifiable copy of string */
rawname = pstrdup(*newval);
/*
* We used to try to check that the named schemas exist, but there are
* many valid use-cases for having search_path settings that include
* schemas that don't exist; and often, we are not inside a transaction
* here and so can't consult the system catalogs anyway. So now, the only
* requirement is syntactic validity of the identifier list.
*/
/*
* Checking only the syntactic validity also allows us to use the search
* path cache (if available) to avoid calling SplitIdentifierString() on
* the same string repeatedly.
*/
if (use_cache)
{
spcache_init();
roleid = GetUserId();
if (spcache_lookup(searchPath, roleid) != NULL)
return true;
}
/*
* Ensure validity check succeeds before creating cache entry.
*/
rawname = pstrdup(searchPath); /* need a modifiable copy */
/* Parse string into list of identifiers */
if (!SplitIdentifierString(rawname, ',', &namelist))
@ -4605,6 +4653,10 @@ check_search_path(char **newval, void **extra, GucSource source)
pfree(rawname);
list_free(namelist);
/* create empty cache entry */
if (use_cache)
(void) spcache_insert(searchPath, roleid);
return true;
}