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Clean up grammar a bit

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Simplify the grammar specification of substring() and overlay() a bit,
simplify and update some comments.

Reviewed-by: Pavel Stehule <pavel.stehule@gmail.com>
Reviewed-by: Vik Fearing <vik@postgresfriends.org>
Reviewed-by: Fabien COELHO <coelho@cri.ensmp.fr>
Discussion: https://www.postgresql.org/message-id/flat/a15db31c-d0f8-8ce0-9039-578a31758adb%402ndquadrant.com
This commit is contained in:
Peter Eisentraut 2020-06-29 10:36:52 +02:00
parent 68de1440c7
commit aafefb4dcb
1 changed files with 23 additions and 50 deletions
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73
src/backend/parser/gram.y
View File

@ -452,7 +452,6 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
%type <list> extract_list overlay_list position_list
%type <list> substr_list trim_list
%type <list> opt_interval interval_second
%type <node> overlay_placing substr_from substr_for
%type <str> unicode_normal_form
%type <boolean> opt_instead
@ -13797,11 +13796,6 @@ func_expr_common_subexpr:
}
| OVERLAY '(' overlay_list ')'
{
/* overlay(A PLACING B FROM C FOR D) is converted to
* overlay(A, B, C, D)
* overlay(A PLACING B FROM C) is converted to
* overlay(A, B, C)
*/
$$ = (Node *) makeFuncCall(SystemFuncName("overlay"), $3, @1);
}
| POSITION '(' position_list ')'
@ -14437,63 +14431,45 @@ unicode_normal_form:
| NFKD { $$ = "nfkd"; }
;
/* OVERLAY() arguments
* SQL99 defines the OVERLAY() function:
* o overlay(text placing text from int for int)
* o overlay(text placing text from int)
* and similarly for binary strings
*/
/* OVERLAY() arguments */
overlay_list:
a_expr overlay_placing substr_from substr_for
a_expr PLACING a_expr FROM a_expr FOR a_expr
{
$$ = list_make4($1, $2, $3, $4);
/* overlay(A PLACING B FROM C FOR D) is converted to overlay(A, B, C, D) */
$$ = list_make4($1, $3, $5, $7);
}
| a_expr overlay_placing substr_from
| a_expr PLACING a_expr FROM a_expr
{
$$ = list_make3($1, $2, $3);
/* overlay(A PLACING B FROM C) is converted to overlay(A, B, C) */
$$ = list_make3($1, $3, $5);
}
;
overlay_placing:
PLACING a_expr
{ $$ = $2; }
;
/* position_list uses b_expr not a_expr to avoid conflict with general IN */
position_list:
b_expr IN_P b_expr { $$ = list_make2($3, $1); }
| /*EMPTY*/ { $$ = NIL; }
;
/* SUBSTRING() arguments
* SQL9x defines a specific syntax for arguments to SUBSTRING():
* o substring(text from int for int)
* o substring(text from int) get entire string from starting point "int"
* o substring(text for int) get first "int" characters of string
* o substring(text from pattern) get entire string matching pattern
* o substring(text from pattern for escape) same with specified escape char
* We also want to support generic substring functions which accept
* the usual generic list of arguments. So we will accept both styles
* here, and convert the SQL9x style to the generic list for further
* processing. - thomas 2000-11-28
*/
/* SUBSTRING() arguments */
substr_list:
a_expr substr_from substr_for
a_expr FROM a_expr FOR a_expr
{
$$ = list_make3($1, $2, $3);
$$ = list_make3($1, $3, $5);
}
| a_expr substr_for substr_from
| a_expr FOR a_expr FROM a_expr
{
/* not legal per SQL99, but might as well allow it */
$$ = list_make3($1, $3, $2);
/* not legal per SQL, but might as well allow it */
$$ = list_make3($1, $5, $3);
}
| a_expr substr_from
| a_expr FROM a_expr
{
$$ = list_make2($1, $2);
$$ = list_make2($1, $3);
}
| a_expr substr_for
| a_expr FOR a_expr
{
/* not legal per SQL */
/*
* Since there are no cases where this syntax allows
* a textual FOR value, we forcibly cast the argument
@ -14504,9 +14480,13 @@ substr_list:
* is unknown or doesn't have an implicit cast to int4.
*/
$$ = list_make3($1, makeIntConst(1, -1),
makeTypeCast($2,
makeTypeCast($3,
SystemTypeName("int4"), -1));
}
/*
* We also want to support generic substring functions that
* accept the usual generic list of arguments.
*/
| expr_list
{
$$ = $1;
@ -14515,13 +14495,6 @@ substr_list:
{ $$ = NIL; }
;
substr_from:
FROM a_expr { $$ = $2; }
;
substr_for: FOR a_expr { $$ = $2; }
;
trim_list: a_expr FROM expr_list { $$ = lappend($3, $1); }
| FROM expr_list { $$ = $2; }
| expr_list { $$ = $1; }