subject:"\[HACKERS\] \[PATCH\] Add two\-arg for of current

Re: [HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

2017-11-02 Thread Peter Eisentraut

On 11/1/17 14:02, Nico Williams wrote:
> There already _is_ a two-argument form of current_setting() that yours
> somewhat conflicts with:
> 
>current_setting(setting_name [, missing_ok ])
> 
> https://www.postgresql.org/docs/current/static/functions-admin.html
> 
> I often use
> 
>   coalesce(current_setting(setting_name, true), default_value_here)
> 
> as an implementation of current_setting() with a default value.

That appears to address this use case then.  Do we need the new proposed
variant still?

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Peter Eisentraut  http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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Re: [HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

2017-11-01 Thread David Christensen


> On Nov 1, 2017, at 1:02 PM, Nico Williams  wrote:
> 
> On Thu, Mar 19, 2015 at 05:41:02PM -0500, David Christensen wrote:
>> 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.:
> 
> There already _is_ a two-argument form of current_setting() that yours
> somewhat conflicts with:
> 
>   current_setting(setting_name [, missing_ok ])
> 
> https://www.postgresql.org/docs/current/static/functions-admin.html


Apologies; I have no idea how this email got re-sent, but it is quite old and a 
mistake.

David
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David Christensen
End Point Corporation
da...@endpoint.com
785-727-1171





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Re: [HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

2017-11-01 Thread Nico Williams

On Thu, Mar 19, 2015 at 05:41:02PM -0500, David Christensen wrote:
> 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.:

There already _is_ a two-argument form of current_setting() that yours
somewhat conflicts with:

   current_setting(setting_name [, missing_ok ])

https://www.postgresql.org/docs/current/static/functions-admin.html

I often use

  coalesce(current_setting(setting_name, true), default_value_here)

as an implementation of current_setting() with a default value.

You could treat booleans as the second argument as a missing_ok argument
instead of a default value, since _currently_ current_setting() only
returns TEXT.

But if ever GUCs are allowed to have values of other types, then your
two-argument current_setting() will conflict with boolean GUCs.

There are several ways to prevent such a future conflict.  Here are
some:

 - make a two-argument current_setting() for boolean GUCs treat the
   second argument as a default value (since there are no such GUCs
   today, this won't break anything)

 - use a new function name

 - use a three-argument current_setting()

The third option seems very lame to me.  So I'd argue for either of the
other two.

Nico
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Re: [HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

2017-11-01 Thread David G. Johnston

On Thu, Mar 19, 2015 at 3:41 PM, David Christensen 
wrote:

> 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.:
>
>   -- returns current setting of foo.bar, or 'default' if not set
>   SELECT current_setting('foo.bar', 'default')
>

This doesn't actually change the GUC in the system, right?  Do we want a
side-effect version of this?

There is already a two-arg form where the second argument is a boolean -
there needs to be tests that ensure proper behavior and function lookup
resolution.

No docs.

David J.

Re: [HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

2017-11-01 Thread Pavel Stehule

Hi

better to send it as attachment

Regards

Pavel

2015-03-19 23:41 GMT+01:00 David Christensen :

> 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_

[HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

2017-11-01 Thread David Christensen

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

[HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

2017-03-29 Thread David Christensen

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

Re: [HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

Re: [HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

Re: [HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

Re: [HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

Re: [HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

[HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

[HACKERS] [PATCH] Add two-arg for of current_setting(NAME, FALLBACK)

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