From 361bfc35724aac207f7a013336e058704fbadf60 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter_e@gmx.net>
Date: Wed, 22 Oct 2008 11:00:34 +0000
Subject: [PATCH] SQL:2008 alternative syntax for LIMIT/OFFSET: OFFSET num
{ROW|ROWS} FETCH {FIRST|NEXT} [num] {ROW|ROWS} ONLY
---
doc/src/sgml/ref/select.sgml | 48 ++++++++++++++++++++++++----
doc/src/sgml/ref/select_into.sgml | 5 +--
doc/src/sgml/ref/values.sgml | 16 ++++++----
src/backend/catalog/sql_features.txt | 18 +++++------
src/backend/parser/gram.y | 44 +++++++++++++++++++++++--
src/backend/parser/keywords.c | 4 +--
6 files changed, 108 insertions(+), 27 deletions(-)
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index f73ca6ed64..91a756b3ae 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -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>
diff --git a/doc/src/sgml/ref/select_into.sgml b/doc/src/sgml/ref/select_into.sgml
index de9a86a878..cbe46cf763 100644
--- a/doc/src/sgml/ref/select_into.sgml
+++ b/doc/src/sgml/ref/select_into.sgml
@@ -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>
diff --git a/doc/src/sgml/ref/values.sgml b/doc/src/sgml/ref/values.sgml
index 23b84d7820..ef605f818f 100644
--- a/doc/src/sgml/ref/values.sgml
+++ b/doc/src/sgml/ref/values.sgml
@@ -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>
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index 4c50a22a0a..b90856fafb 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -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
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index aa5f33b411..3ab62b23cb 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -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
diff --git a/src/backend/parser/keywords.c b/src/backend/parser/keywords.c
index 7c6aa71572..608e80e0f5 100644
--- a/src/backend/parser/keywords.c
+++ b/src/backend/parser/keywords.c
@@ -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},