Hi better to send it as attachment
Regards Pavel 2015-03-19 23:41 GMT+01:00 David Christensen <da...@endpoint.com>: > The two-arg form of the current_setting() function will allow a > fallback value to be returned instead of throwing an error when an > unknown GUC is provided. This would come in most useful when using > custom GUCs; e.g.: > > -- errors out if the 'foo.bar' setting is unset > SELECT current_setting('foo.bar'); > > -- returns current setting of foo.bar, or 'default' if not set > SELECT current_setting('foo.bar', 'default') > > This would save you having to wrap the use of the function in an > exception block just to catch and utilize a default setting value > within a function. > --- > src/backend/utils/misc/guc.c | 50 ++++++++++++++++++++++++++++++ > ++++++--- > src/include/catalog/pg_proc.h | 2 ++ > src/include/utils/builtins.h | 1 + > src/include/utils/guc.h | 1 + > src/test/regress/expected/guc.out | 19 +++++++++++++++ > src/test/regress/sql/guc.sql | 12 ++++++++++ > 6 files changed, 82 insertions(+), 3 deletions(-) > > diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c > index 26275bd..002a926 100644 > --- a/src/backend/utils/misc/guc.c > +++ b/src/backend/utils/misc/guc.c > @@ -7703,13 +7703,32 @@ ShowAllGUCConfig(DestReceiver *dest) > char * > GetConfigOptionByName(const char *name, const char **varname) > { > + return GetConfigOptionByNameFallback(name, NULL, varname); > +} > + > +/* > + * Return GUC variable value by name; optionally return canonical form of > + * name. If GUC is NULL then optionally return a fallback value instead > of an > + * error. Return value is palloc'd. > + */ > +char * > +GetConfigOptionByNameFallback(const char *name, const char > *default_value, const char **varname) > +{ > struct config_generic *record; > > record = find_option(name, false, ERROR); > if (record == NULL) > - ereport(ERROR, > - (errcode(ERRCODE_UNDEFINED_OBJECT), > - errmsg("unrecognized configuration parameter > \"%s\"", name))); > + { > + if (default_value) { > + return pstrdup(default_value); > + } > + else > + { > + 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), > @@ -8008,6 +8027,31 @@ show_config_by_name(PG_FUNCTION_ARGS) > } > > /* > + * show_config_by_name_fallback - equiv to SHOW X command but implemented > as > + * a function. If X does not exist, return a fallback datum instead of > erroring > + */ > +Datum > +show_config_by_name_fallback(PG_FUNCTION_ARGS) > +{ > + char *varname; > + char *varfallback; > + char *varval; > + > + /* Get the GUC variable name */ > + varname = TextDatumGetCString(PG_GETARG_DATUM(0)); > + > + /* Get the fallback value */ > + varfallback = TextDatumGetCString(PG_GETARG_DATUM(1)); > + > + /* Get the value */ > + varval = GetConfigOptionByNameFallback(varname, varfallback, > NULL); > + > + /* Convert to text */ > + PG_RETURN_TEXT_P(cstring_to_text(varval)); > +} > + > + > +/* > * show_all_settings - equiv to SHOW ALL command but implemented as > * a Table Function. > */ > diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h > index 6a757f3..71efed2 100644 > --- a/src/include/catalog/pg_proc.h > +++ b/src/include/catalog/pg_proc.h > @@ -3025,6 +3025,8 @@ DESCR("convert bitstring to int8"); > > DATA(insert OID = 2077 ( current_setting PGNSP PGUID 12 1 0 0 0 f f > f f t f s 1 0 25 "25" _null_ _null_ _null_ _null_ show_config_by_name > _null_ _null_ _null_ )); > DESCR("SHOW X as a function"); > +DATA(insert OID = 3280 ( current_setting PGNSP PGUID 12 1 0 0 0 f f > f f t f s 2 0 25 "25 25" _null_ _null_ _null_ _null_ > show_config_by_name_fallback _null_ _null_ _null_ )); > +DESCR("SHOW X as a function"); > DATA(insert OID = 2078 ( set_config PGNSP PGUID 12 1 0 0 0 f f > f f f f v 3 0 25 "25 25 16" _null_ _null_ _null_ _null_ set_config_by_name > _null_ _null_ _null_ )); > DESCR("SET X as a function"); > DATA(insert OID = 2084 ( pg_show_all_settings PGNSP PGUID 12 1 1000 0 0 > f f f f t t s 0 0 2249 "" > "{25,25,25,25,25,25,25,25,25,25,25,1009,25,25,25,23}" > "{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}" "{name,setting,unit,category, > short_desc,extra_desc,context,vartype,source,min_val,max_ > val,enumvals,boot_val,reset_val,sourcefile,sourceline}" _null_ > show_all_settings _null_ _null_ _null_ )); > diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h > index bc4517d..e3d9fbb 100644 > --- a/src/include/utils/builtins.h > +++ b/src/include/utils/builtins.h > @@ -1088,6 +1088,7 @@ extern Datum quote_nullable(PG_FUNCTION_ARGS); > > /* guc.c */ > extern Datum show_config_by_name(PG_FUNCTION_ARGS); > +extern Datum show_config_by_name_fallback(PG_FUNCTION_ARGS); > extern Datum set_config_by_name(PG_FUNCTION_ARGS); > extern Datum show_all_settings(PG_FUNCTION_ARGS); > > diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h > index d3100d1..145ad5d 100644 > --- a/src/include/utils/guc.h > +++ b/src/include/utils/guc.h > @@ -352,6 +352,7 @@ extern int set_config_option(const char *name, const > char *value, > bool is_reload); > extern void AlterSystemSetConfigFile(AlterSystemStmt *setstmt); > extern char *GetConfigOptionByName(const char *name, const char > **varname); > +extern char *GetConfigOptionByNameFallback(const char *name, const char > *fallback, const char **varname); > extern void GetConfigOptionByNum(int varnum, const char **values, bool > *noshow); > extern int GetNumConfigOptions(void); > > diff --git a/src/test/regress/expected/guc.out > b/src/test/regress/expected/guc.out > index 4f0065c..905969b 100644 > --- a/src/test/regress/expected/guc.out > +++ b/src/test/regress/expected/guc.out > @@ -736,3 +736,22 @@ NOTICE: text search configuration "no_such_config" > does not exist > select func_with_bad_set(); > ERROR: invalid value for parameter "default_text_search_config": > "no_such_config" > reset check_function_bodies; > +-- check multi-arg custom current_setting > +-- this should error: > +select current_setting('nosuch.setting'); > +ERROR: unrecognized configuration parameter "nosuch.setting" > +-- this should return 'fallback' > +select current_setting('nosuch.setting','fallback'); > + current_setting > +----------------- > + fallback > +(1 row) > + > +-- this should return 'nada', not 'fallback' > +set nosuch.setting = 'nada'; > +select current_setting('nosuch.setting','fallback'); > + current_setting > +----------------- > + nada > +(1 row) > + > diff --git a/src/test/regress/sql/guc.sql b/src/test/regress/sql/guc.sql > index 3de8a6b..48c0bed 100644 > --- a/src/test/regress/sql/guc.sql > +++ b/src/test/regress/sql/guc.sql > @@ -275,3 +275,15 @@ set default_text_search_config = no_such_config; > select func_with_bad_set(); > > reset check_function_bodies; > + > +-- check multi-arg custom current_setting > + > +-- this should error: > +select current_setting('nosuch.setting'); > + > +-- this should return 'fallback' > +select current_setting('nosuch.setting','fallback'); > + > +-- this should return 'nada', not 'fallback' > +set nosuch.setting = 'nada'; > +select current_setting('nosuch.setting','fallback'); > -- > 2.3.3 > > > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers >