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Commitbe4cd18

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Allow mixing of traditional and SQL:2008 LIMIT/OFFSET syntax. Being rigid
about it doesn't simplify the grammar at all, and it does invite confusionamong those who only read the SELECT syntax summary and not the full details.Per gripe from Jaime Casanova.
1 parent514c3f1 commitbe4cd18

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2 files changed

+47
-42
lines changed

2 files changed

+47
-42
lines changed

‎doc/src/sgml/ref/select.sgml

Lines changed: 6 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
2-
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.122 2009/05/03 20:45:43 tgl Exp $
2+
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.123 2009/08/18 23:40:20 tgl Exp $
33
PostgreSQL documentation
44
-->
55

@@ -1005,14 +1005,15 @@ OFFSET <replaceable class="parameter">start</replaceable>
10051005

10061006
<para>
10071007
SQL:2008 introduced a different syntax to achieve the same thing,
1008-
which PostgreSQL also supports. It is:
1008+
which<productname>PostgreSQL</> also supports. It is:
10091009
<synopsis>
10101010
OFFSET <replaceable class="parameter">start</replaceable> { ROW | ROWS }
10111011
FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY
10121012
</synopsis>
1013-
Both clauses are optional, but if present
1014-
the <literal>OFFSET</literal> clause must come before
1015-
the <literal>FETCH</literal> clause. <literal>ROW</literal>
1013+
According to the standard, the <literal>OFFSET</literal> clause must come
1014+
before the <literal>FETCH</literal> clause if both are present; but
1015+
<productname>PostgreSQL</> is laxer and allows either order.
1016+
<literal>ROW</literal>
10161017
and <literal>ROWS</literal> as well as <literal>FIRST</literal>
10171018
and <literal>NEXT</literal> are noise words that don't influence
10181019
the effects of these clauses. In this syntax, when using expressions

‎src/backend/parser/gram.y

Lines changed: 41 additions & 37 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@
1111
*
1212
*
1313
* IDENTIFICATION
14-
* $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.676 2009/08/02 22:14:52 tgl Exp $
14+
* $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.677 2009/08/18 23:40:20 tgl Exp $
1515
*
1616
* HISTORY
1717
* AUTHORDATEMAJOR EVENT
@@ -331,7 +331,8 @@ static TypeName *TableFuncTypeName(List *columns);
331331
%type<ival>opt_columneventcursor_optionsopt_holdopt_set_data
332332
%type<objtype>reindex_typedrop_typecomment_type
333333

334-
%type<node>fetch_directionselect_limit_valueselect_offset_value
334+
%type<node>fetch_directionlimit_clauseselect_limit_value
335+
offset_clauseselect_offset_value
335336
select_offset_value2opt_select_fetch_first_value
336337
%type<ival>row_or_rowsfirst_or_next
337338

@@ -7228,14 +7229,20 @@ sortby:a_expr USING qual_all_Op opt_nulls_order
72287229

72297230

72307231
select_limit:
7231-
LIMIT select_limit_value OFFSET select_offset_value
7232-
{$$ = list_make2($4,$2); }
7233-
| OFFSET select_offset_value LIMIT select_limit_value
7234-
{$$ = list_make2($2,$4); }
7235-
| LIMIT select_limit_value
7236-
{$$ = list_make2(NULL,$2); }
7237-
| OFFSET select_offset_value
7238-
{$$ = list_make2($2,NULL); }
7232+
limit_clause offset_clause{$$ = list_make2($2,$1); }
7233+
| offset_clause limit_clause{$$ = list_make2($1,$2); }
7234+
| limit_clause{$$ = list_make2(NULL,$1); }
7235+
| offset_clause{$$ = list_make2($1,NULL); }
7236+
;
7237+
7238+
opt_select_limit:
7239+
select_limit{$$ =$1; }
7240+
|/* EMPTY*/{$$ = list_make2(NULL,NULL); }
7241+
;
7242+
7243+
limit_clause:
7244+
LIMIT select_limit_value
7245+
{$$ =$2; }
72397246
| LIMIT select_limit_value',' select_offset_value
72407247
{
72417248
/* Disabled because it was too confusing, bjm 2002-02-18*/
@@ -7245,19 +7252,17 @@ select_limit:
72457252
errhint("Use separate LIMIT and OFFSET clauses."),
72467253
parser_errposition(@1)));
72477254
}
7248-
/* SQL:2008 syntax variants*/
7249-
| OFFSET select_offset_value2 row_or_rows
7250-
{$$ = list_make2($2,NULL); }
7255+
/* SQL:2008 syntax*/
72517256
| FETCH first_or_next opt_select_fetch_first_value row_or_rows ONLY
7252-
{$$ = list_make2(NULL,$3); }
7253-
| OFFSET select_offset_value2 row_or_rows FETCH first_or_next opt_select_fetch_first_value row_or_rows ONLY
7254-
{$$ = list_make2($2,$6); }
7257+
{$$ =$3; }
72557258
;
72567259

7257-
opt_select_limit:
7258-
select_limit{$$ =$1; }
7259-
|/* EMPTY*/
7260-
{$$ = list_make2(NULL,NULL); }
7260+
offset_clause:
7261+
OFFSET select_offset_value
7262+
{$$ =$2; }
7263+
/* SQL:2008 syntax*/
7264+
| OFFSET select_offset_value2 row_or_rows
7265+
{$$ =$2; }
72617266
;
72627267

72637268
select_limit_value:
@@ -7269,19 +7274,20 @@ select_limit_value:
72697274
}
72707275
;
72717276

7277+
select_offset_value:
7278+
a_expr{$$ =$1; }
7279+
;
7280+
72727281
/*
72737282
* Allowing full expressions without parentheses causes various parsing
72747283
* problems with the trailing ROW/ROWS key words. SQL only calls for
7275-
* constants, so we allow the rest only with parentheses.
7284+
* constants, so we allow the rest only with parentheses. If omitted,
7285+
* default to 1.
72767286
*/
72777287
opt_select_fetch_first_value:
7278-
SignedIconst{$$ = makeIntConst($1,@1); }
7279-
|'(' a_expr')'{$$ =$2; }
7280-
|/*EMPTY*/{$$ = makeIntConst(1, -1); }
7281-
;
7282-
7283-
select_offset_value:
7284-
a_expr{$$ =$1; }
7288+
SignedIconst{$$ = makeIntConst($1,@1); }
7289+
|'(' a_expr')'{$$ =$2; }
7290+
|/*EMPTY*/{$$ = makeIntConst(1, -1); }
72857291
;
72867292

72877293
/*
@@ -7293,16 +7299,14 @@ select_offset_value2:
72937299
;
72947300

72957301
/* noise words*/
7296-
row_or_rows:
7297-
ROW{$$ =0; }
7298-
| ROWS{$$ =0; }
7299-
;
7302+
row_or_rows: ROW{$$ =0; }
7303+
| ROWS{$$ =0; }
7304+
;
7305+
7306+
first_or_next: FIRST_P{$$ =0; }
7307+
| NEXT{$$ =0; }
7308+
;
73007309

7301-
/* noise words*/
7302-
first_or_next:
7303-
FIRST_P{$$ =0; }
7304-
| NEXT{$$ =0; }
7305-
;
73067310

73077311
group_clause:
73087312
GROUP_P BY expr_list{$$ =$3; }

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