On Fri, Aug 9, 2013 at 12:23:59PM -0400, Bruce Momjian wrote:
> Yes, I have thought about this some more and another problem is that
> rtrim/btrim/ltrim() use the source string first, so having trim() have
> the source string second when using a comma is very confusing, e.g.:
>
> -- with patch
> SELECT trim('x', 'xabcx');
> btrim
> -------
> abc
>
> -- btrim
> SELECT btrim('xabcx', 'x');
> btrim
> -------
> abc
>
> I think we can either document what we have, or remove the ability to
> use comma with trim(). If we go with documentation, it is going to look
> confusing as the optional modifier is going to be on the source string,
> e.g.:
>
> SELECT trim(both 'xabcx', 'x');
> btrim
> -------
> abc
>
> We could modify the grammar to force the modifier on the second
> argument, but that is more parser states for limited value.
[ moved to hackers ]
Based on my research, I am now proposing a new, attached patch which
eliminates comma in all places in TRIM, e.g. this is no longer valid
either:
SELECT trim(BOTH FROM 'abc', 'a');
btrim
-------
bc
(1 row)
I believe the flexible TRIM syntax was introduced when TRIM was added in
1997:
commit 570620c5698b0c76b26a3ec71692df29375cad16
Author: Thomas G. Lockhart <[email protected]>
Date: Mon Sep 1 06:00:35 1997 +0000
Add SQL92 string handling features (SUBSTRING, TRIM, EXTRACT).
We would now only support the documented TRIM syntax.
--
Bruce Momjian <[email protected]> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
new file mode 100644
index 22e82ba..aa88cfb
*** a/src/backend/parser/gram.y
--- b/src/backend/parser/gram.y
*************** substr_from:
*** 11991,11999 ****
substr_for: FOR a_expr { $$ = $2; }
;
! trim_list: a_expr FROM expr_list { $$ = lappend($3, $1); }
! | FROM expr_list { $$ = $2; }
! | expr_list { $$ = $1; }
;
in_expr: select_with_parens
--- 11991,11999 ----
substr_for: FOR a_expr { $$ = $2; }
;
! trim_list: a_expr FROM a_expr { $$ = list_make2($3, $1); }
! | FROM a_expr { $$ = list_make1($2); }
! | a_expr { $$ = list_make1($1); }
;
in_expr: select_with_parens
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