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Cache opaque handle for GUC option to avoid repeasted lookups.

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When setting GUCs from proconfig, performance is important, and hash
lookups in the GUC table are significant.

Per suggestion from Robert Haas.

Discussion: https://postgr.es/m/CA+TgmoYpKxhR3HOD9syK2XwcAUVPa0+ba0XPnwWBcYxtKLkyxA@mail.gmail.com
Reviewed-by: John Naylor
This commit is contained in:
Jeff Davis
2023-12-08 11:16:01 -08:00
parent c9c0589fda
commit 867dd2dc87
4 changed files with 84 additions and 14 deletions
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57
src/backend/utils/misc/guc.c
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@ -3329,10 +3329,10 @@ set_config_option(const char *name, const char *value,
else
srole = BOOTSTRAP_SUPERUSERID;
return set_config_option_ext(name, value,
context, source, srole,
action, changeVal, elevel,
is_reload);
return set_config_with_handle(name, NULL, value,
context, source, srole,
action, changeVal, elevel,
is_reload);
}
/*
@ -3355,6 +3355,27 @@ set_config_option_ext(const char *name, const char *value,
GucContext context, GucSource source, Oid srole,
GucAction action, bool changeVal, int elevel,
bool is_reload)
{
return set_config_with_handle(name, NULL, value,
context, source, srole,
action, changeVal, elevel,
is_reload);
}
/*
* set_config_with_handle: takes an optional 'handle' argument, which can be
* obtained by the caller from get_config_handle().
*
* This should be used by callers which repeatedly set the same config
* option(s), and want to avoid the overhead of a hash lookup each time.
*/
int
set_config_with_handle(const char *name, config_handle *handle,
const char *value,
GucContext context, GucSource source, Oid srole,
GucAction action, bool changeVal, int elevel,
bool is_reload)
{
struct config_generic *record;
union config_var_val newval_union;
@ -3395,9 +3416,15 @@ set_config_option_ext(const char *name, const char *value,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot set parameters during a parallel operation")));
record = find_option(name, true, false, elevel);
if (record == NULL)
return 0;
/* if handle is specified, no need to look up option */
if (!handle)
{
record = find_option(name, true, false, elevel);
if (record == NULL)
return 0;
}
else
record = handle;
/*
* Check if the option can be set at this time. See guc.h for the precise
@ -4166,6 +4193,22 @@ set_config_option_ext(const char *name, const char *value,
}
/*
* Retrieve a config_handle for the given name, suitable for calling
* set_config_with_handle(). Only return handle to permanent GUC.
*/
config_handle *
get_config_handle(const char *name)
{
struct config_generic *gen = find_option(name, false, false, 0);
if (gen && ((gen->flags & GUC_CUSTOM_PLACEHOLDER) == 0))
return gen;
return NULL;
}
/*
* Set the fields for source file and line number the setting came from.
*/