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SQL:2008 alternative syntax for LIMIT/OFFSET:

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OFFSET num {ROW|ROWS} FETCH {FIRST|NEXT} [num] {ROW|ROWS} ONLY
REL8_5_ALPHA1_BRANCH
Peter Eisentraut 17 years ago
parent e6ae3b5dbf
commit 361bfc3572
6 changed files with 108 additions and 27 deletions
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  1. 48
      doc/src/sgml/ref/select.sgml
  2. 5
      doc/src/sgml/ref/select_into.sgml
  3. 16
      doc/src/sgml/ref/values.sgml
  4. 18
      src/backend/catalog/sql_features.txt
  5. 44
      src/backend/parser/gram.y
  6. 4
      src/backend/parser/keywords.c

48
doc/src/sgml/ref/select.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.106 2008/10/07 19:27:04 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.107 2008/10/22 11:00:33 petere Exp $
PostgreSQL documentation
-->
@ -30,7 +30,8 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
[ { UNION | INTERSECT | EXCEPT } [ ALL ] <replaceable class="parameter">select</replaceable> ]
[ ORDER BY <replaceable class="parameter">expression</replaceable> [ ASC | DESC | USING <replaceable class="parameter">operator</replaceable> ] [ NULLS { FIRST | LAST } ] [, ...] ]
[ LIMIT { <replaceable class="parameter">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="parameter">start</replaceable> ]
[ OFFSET <replaceable class="parameter">start</replaceable> [ ROW | ROWS ] ]
[ FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY ]
[ FOR { UPDATE | SHARE } [ OF <replaceable class="parameter">table_name</replaceable> [, ...] ] [ NOWAIT ] [...] ]
where <replaceable class="parameter">from_item</replaceable> can be one of:
@ -150,7 +151,7 @@ and <replaceable class="parameter">with_query</replaceable> is:
<listitem>
<para>
If the <literal>LIMIT</literal> or <literal>OFFSET</literal>
If the <literal>LIMIT</literal> (or <literal>FETCH FIRST</literal>) or <literal>OFFSET</literal>
clause is specified, the <command>SELECT</command> statement
only returns a subset of the result rows. (See <xref
linkend="sql-limit" endterm="sql-limit-title"> below.)
@ -891,6 +892,24 @@ OFFSET <replaceable class="parameter">start</replaceable>
class="parameter">count</replaceable> rows to be returned.
</para>
<para>
SQL:2008 introduced a different syntax to achieve the same thing,
which PostgreSQL also supports. It is:
<synopsis>
OFFSET <replaceable class="parameter">start</replaceable> { ROW | ROWS }
FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY
</synopsis>
Both clauses are optional, but if present
the <literal>OFFSET</literal> clause must come before
the <literal>FETCH</literal> clause. <literal>ROW</literal>
and <literal>ROWS</literal> as well as <literal>FIRST</literal>
and <literal>NEXT</literal> are noise words that don't influence
the effects of these clauses. When using expressions other than
constants for the offset or fetch count, parentheses will be
necessary in most cases. If the fetch count is omitted, it
defaults to 1.
</para>
<para>
When using <literal>LIMIT</>, it is a good idea to use an
<literal>ORDER BY</> clause that constrains the result rows into a
@ -1337,13 +1356,30 @@ SELECT distributors.* WHERE distributors.name = 'Westward';
</para>
</refsect2>
<refsect2>
<title><literal>LIMIT</literal> and <literal>OFFSET</literal></title>
<para>
The clauses <literal>LIMIT</literal> and <literal>OFFSET</literal>
are <productname>PostgreSQL</productname>-specific syntax, also
used by <productname>MySQL</productname>. The SQL:2008 standard
has introduced the clauses <literal>OFFSET ... FETCH {FIRST|NEXT}
...</literal> for the same functionality, as shown above
in <xref linkend="sql-limit" endterm="sql-limit-title">, and this
syntax is also used by <productname>IBM DB2</productname>.
(Applications written for <productname>Oracle</productname>
frequently use a workaround involving the automatically
generated <literal>rownum</literal> column, not available in
PostgreSQL, to implement the effects of these clauses.)
</para>
</refsect2>
<refsect2>
<title>Nonstandard Clauses</title>
<para>
The clauses <literal>DISTINCT ON</literal>,
<literal>LIMIT</literal>, and <literal>OFFSET</literal> are not
defined in the SQL standard.
The clause <literal>DISTINCT ON</literal> is not defined in the
SQL standard.
</para>
</refsect2>
</refsect1>

5
doc/src/sgml/ref/select_into.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/select_into.sgml,v 1.41 2008/10/04 21:56:52 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/select_into.sgml,v 1.42 2008/10/22 11:00:34 petere Exp $
PostgreSQL documentation
-->
@ -31,7 +31,8 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
[ { UNION | INTERSECT | EXCEPT } [ ALL ] <replaceable class="parameter">select</replaceable> ]
[ ORDER BY <replaceable class="parameter">expression</replaceable> [ ASC | DESC | USING <replaceable class="parameter">operator</replaceable> ] [ NULLS { FIRST | LAST } ] [, ...] ]
[ LIMIT { <replaceable class="parameter">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="parameter">start</replaceable> ]
[ OFFSET <replaceable class="parameter">start</replaceable> [ ROW | ROWS ] ]
[ FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY ]
[ FOR { UPDATE | SHARE } [ OF <replaceable class="parameter">table_name</replaceable> [, ...] ] [ NOWAIT ] [...] ]
</synopsis>
</refsynopsisdiv>

16
doc/src/sgml/ref/values.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/values.sgml,v 1.4 2007/02/01 00:28:19 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/values.sgml,v 1.5 2008/10/22 11:00:34 petere Exp $
PostgreSQL documentation
-->
@ -23,7 +23,8 @@ PostgreSQL documentation
VALUES ( <replaceable class="PARAMETER">expression</replaceable> [, ...] ) [, ...]
[ ORDER BY <replaceable class="parameter">sort_expression</replaceable> [ ASC | DESC | USING <replaceable class="parameter">operator</replaceable> ] [, ...] ]
[ LIMIT { <replaceable class="parameter">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="parameter">start</replaceable> ]
[ OFFSET <replaceable class="parameter">start</replaceable> [ ROW | ROWS ] ]
[ FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY ]
</synopsis>
</refsynopsisdiv>
@ -48,8 +49,10 @@ VALUES ( <replaceable class="PARAMETER">expression</replaceable> [, ...] ) [, ..
<para>
Within larger commands, <command>VALUES</> is syntactically allowed
anywhere that <command>SELECT</> is. Because it is treated like a
<command>SELECT</> by the grammar, it is possible to use the <literal>ORDER
BY</>, <literal>LIMIT</>, and <literal>OFFSET</> clauses with a
<command>SELECT</> by the grammar, it is possible to use
the <literal>ORDER BY</>, <literal>LIMIT</> (or
equivalently <literal>FETCH FIRST</literal>),
and <literal>OFFSET</> clauses with a
<command>VALUES</> command.
</para>
</refsect1>
@ -227,9 +230,10 @@ WHERE ip_address IN (VALUES('192.168.0.1'::inet), ('192.168.0.10'), ('192.168.1.
<title>Compatibility</title>
<para>
<command>VALUES</command> conforms to the SQL standard, except that
<command>VALUES</command> conforms to the SQL standard.
<literal>LIMIT</literal> and <literal>OFFSET</literal> are
<productname>PostgreSQL</productname> extensions.
<productname>PostgreSQL</productname> extensions; see also
under <xref linkend="sql-select" endterm="sql-select-title">.
</para>
</refsect1>

18
src/backend/catalog/sql_features.txt
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@ -319,15 +319,15 @@ F851 <order by clause> in subqueries YES
F852 Top-level <order by clause> in views YES
F855 Nested <order by clause> in <query expression> YES
F856 Nested <fetch first clause> in <query expression> YES
F857 Top-level <fetch first clause> in <query expression> NO same as LIMIT
F858 <fetch first clause> in subqueries NO same as LIMIT
F859 Top-level <fetch first clause> in views NO same as LIMIT
F860 <fetch first row count> in <fetch first clause> NO same as LIMIT
F861 Top-level <result offset clause> in <query expression> NO same as OFFSET
F862 <result offset clause> in subqueries NO same as OFFSET
F863 Nested <result offset clause> in <query expression> NO same as OFFSET
F864 Top-level <result offset clause> in views NO same as OFFSET
F865 <offset row count> in <result offset clause> NO same as OFFSET
F857 Top-level <fetch first clause> in <query expression> YES
F858 <fetch first clause> in subqueries YES
F859 Top-level <fetch first clause> in views YES
F860 <fetch first row count> in <fetch first clause> YES
F861 Top-level <result offset clause> in <query expression> YES
F862 <result offset clause> in subqueries YES
F863 Nested <result offset clause> in <query expression> YES
F864 Top-level <result offset clause> in views YES
F865 <offset row count> in <result offset clause> YES
S011 Distinct data types NO
S011 Distinct data types 01 USER_DEFINED_TYPES view NO
S023 Basic structured types NO

44
src/backend/parser/gram.y
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@ -11,7 +11,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.627 2008/10/21 08:38:15 petere Exp $
* $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.628 2008/10/22 11:00:34 petere Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
@ -308,6 +308,8 @@ static TypeName *TableFuncTypeName(List *columns);
%type <objtype> reindex_type drop_type comment_type
%type <node> fetch_direction select_limit_value select_offset_value
select_offset_value2 opt_select_fetch_first_value
%type <ival> row_or_rows first_or_next
%type <list> OptSeqOptList SeqOptList
%type <defelt> SeqOptElem
@ -6579,6 +6581,13 @@ select_limit:
errhint("Use separate LIMIT and OFFSET clauses."),
scanner_errposition(@1)));
}
/* SQL:2008 syntax variants */
| OFFSET select_offset_value2 row_or_rows
{ $$ = list_make2($2, NULL); }
| FETCH first_or_next opt_select_fetch_first_value row_or_rows ONLY
{ $$ = list_make2(NULL, $3); }
| OFFSET select_offset_value2 row_or_rows FETCH first_or_next opt_select_fetch_first_value row_or_rows ONLY
{ $$ = list_make2($2, $6); }
;
opt_select_limit:
@ -6596,10 +6605,40 @@ select_limit_value:
}
;
/*
* Allowing full expressions without parentheses causes various parsing
* problems with the trailing ROW/ROWS key words. SQL only calls for
* constants, so we allow the rest only with parentheses.
*/
opt_select_fetch_first_value:
SignedIconst { $$ = makeIntConst($1, @1); }
| '(' a_expr ')' { $$ = $2; }
| /*EMPTY*/ { $$ = makeIntConst(1, -1); }
;
select_offset_value:
a_expr { $$ = $1; }
;
/*
* Again, the trailing ROW/ROWS in this case prevent the full expression
* syntax. c_expr is the best we can do.
*/
select_offset_value2:
c_expr { $$ = $1; }
;
/* noise words */
row_or_rows:
ROW { $$ = 0; }
| ROWS { $$ = 0; }
/* noise words */
first_or_next:
FIRST_P { $$ = 0; }
| NEXT { $$ = 0; }
group_clause:
GROUP_P BY expr_list { $$ = $3; }
| /*EMPTY*/ { $$ = NIL; }
@ -9218,6 +9257,7 @@ Sconst: SCONST { $$ = $1; };
RoleId: ColId { $$ = $1; };
SignedIconst: ICONST { $$ = $1; }
| '+' ICONST { $$ = + $2; }
| '-' ICONST { $$ = - $2; }
;
@ -9351,7 +9391,6 @@ unreserved_keyword:
| EXPLAIN
| EXTERNAL
| FAMILY
| FETCH
| FIRST_P
| FORCE
| FORWARD
@ -9641,6 +9680,7 @@ reserved_keyword:
| END_P
| EXCEPT
| FALSE_P
| FETCH
| FOR
| FOREIGN
| FROM

4
src/backend/parser/keywords.c
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@ -11,7 +11,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/parser/keywords.c,v 1.203 2008/10/21 08:38:15 petere Exp $
* $PostgreSQL: pgsql/src/backend/parser/keywords.c,v 1.204 2008/10/22 11:00:34 petere Exp $
*
*-------------------------------------------------------------------------
*/
@ -166,7 +166,7 @@ const ScanKeyword ScanKeywords[] = {
{"extract", EXTRACT, COL_NAME_KEYWORD},
{"false", FALSE_P, RESERVED_KEYWORD},
{"family", FAMILY, UNRESERVED_KEYWORD},
{"fetch", FETCH, UNRESERVED_KEYWORD},
{"fetch", FETCH, RESERVED_KEYWORD},
{"first", FIRST_P, UNRESERVED_KEYWORD},
{"float", FLOAT_P, COL_NAME_KEYWORD},
{"for", FOR, RESERVED_KEYWORD},

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