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Add an optional missing_ok argument to SQL function current_setting().

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This allows convenient checking for existence of a GUC from SQL, which is
particularly useful when dealing with custom variables.

David Christensen, reviewed by Jeevan Chalke
This commit is contained in:
Tom Lane
2015-07-02 16:40:55 -04:00
parent 7261172430
commit 10fb48d66d
9 changed files with 101 additions and 17 deletions
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53
src/backend/utils/misc/guc.c
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@ -7131,7 +7131,7 @@ ExtractSetVariableArgs(VariableSetStmt *stmt)
case VAR_SET_VALUE:
return flatten_set_variable_args(stmt->name, stmt->args);
case VAR_SET_CURRENT:
return GetConfigOptionByName(stmt->name, NULL);
return GetConfigOptionByName(stmt->name, NULL, false);
default:
return NULL;
}
@ -7200,7 +7200,7 @@ set_config_by_name(PG_FUNCTION_ARGS)
true, 0, false);
/* get the new current value */
new_value = GetConfigOptionByName(name, NULL);
new_value = GetConfigOptionByName(name, NULL, false);
/* Convert return string to text */
PG_RETURN_TEXT_P(cstring_to_text(new_value));
@ -7627,7 +7627,7 @@ GetPGVariableResultDesc(const char *name)
const char *varname;
/* Get the canonical spelling of name */
(void) GetConfigOptionByName(name, &varname);
(void) GetConfigOptionByName(name, &varname, false);
/* need a tuple descriptor representing a single TEXT column */
tupdesc = CreateTemplateTupleDesc(1, false);
@ -7650,7 +7650,7 @@ ShowGUCConfigOption(const char *name, DestReceiver *dest)
char *value;
/* Get the value and canonical spelling of name */
value = GetConfigOptionByName(name, &varname);
value = GetConfigOptionByName(name, &varname, false);
/* need a tuple descriptor representing a single TEXT column */
tupdesc = CreateTemplateTupleDesc(1, false);
@ -7734,19 +7734,30 @@ ShowAllGUCConfig(DestReceiver *dest)
}
/*
* Return GUC variable value by name; optionally return canonical
* form of name. Return value is palloc'd.
* Return GUC variable value by name; optionally return canonical form of
* name. If the GUC is unset, then throw an error unless missing_ok is true,
* in which case return NULL. Return value is palloc'd (but *varname isn't).
*/
char *
GetConfigOptionByName(const char *name, const char **varname)
GetConfigOptionByName(const char *name, const char **varname, bool missing_ok)
{
struct config_generic *record;
record = find_option(name, false, ERROR);
if (record == NULL)
{
if (missing_ok)
{
if (varname)
*varname = NULL;
return NULL;
}
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("unrecognized configuration parameter \"%s\"", name)));
}
if ((record->flags & GUC_SUPERUSER_ONLY) && !superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
@ -8033,14 +8044,34 @@ GetNumConfigOptions(void)
Datum
show_config_by_name(PG_FUNCTION_ARGS)
{
char *varname;
char *varname = TextDatumGetCString(PG_GETARG_DATUM(0));
char *varval;
/* Get the GUC variable name */
varname = TextDatumGetCString(PG_GETARG_DATUM(0));
/* Get the value */
varval = GetConfigOptionByName(varname, NULL, false);
/* Convert to text */
PG_RETURN_TEXT_P(cstring_to_text(varval));
}
/*
* show_config_by_name_missing_ok - equiv to SHOW X command but implemented as
* a function. If X does not exist, suppress the error and just return NULL
* if missing_ok is TRUE.
*/
Datum
show_config_by_name_missing_ok(PG_FUNCTION_ARGS)
{
char *varname = TextDatumGetCString(PG_GETARG_DATUM(0));
bool missing_ok = PG_GETARG_BOOL(1);
char *varval;
/* Get the value */
varval = GetConfigOptionByName(varname, NULL);
varval = GetConfigOptionByName(varname, NULL, missing_ok);
/* return NULL if no such variable */
if (varval == NULL)
PG_RETURN_NULL();
/* Convert to text */
PG_RETURN_TEXT_P(cstring_to_text(varval));