database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-08-28 18:48:04 +03:00
Code Activity

Restructure parsetree representation of DECLARE CURSOR: now it's a

Browse Source 
utility statement (DeclareCursorStmt) with a SELECT query dangling from
it, rather than a SELECT query with a few unusual fields in it.  Add
code to determine whether a planned query can safely be run backwards.
If DECLARE CURSOR specifies SCROLL, ensure that the plan can be run
backwards by adding a Materialize plan node if it can't.  Without SCROLL,
you get an error if you try to fetch backwards from a cursor that can't
handle it.  (There is still some discussion about what the exact
behavior should be, but this is necessary infrastructure in any case.)
Along the way, make EXPLAIN DECLARE CURSOR work.
This commit is contained in:
Tom Lane
2003-03-10 03:53:52 +00:00
parent b9e8ffcd5d
commit aa83bc04e0
40 changed files with 664 additions and 574 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
doc/src/sgml/ref/fetch.sgml
View File

@@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/fetch.sgml,v 1.25 2003/02/04 11:23:58 momjian Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/fetch.sgml,v 1.26 2003/03/10 03:53:49 tgl Exp $
PostgreSQL documentation
-->
@@ -13,7 +13,7 @@ PostgreSQL documentation
FETCH
</refname>
<refpurpose>
retrieve rows from a table using a cursor
retrieve rows from a query using a cursor
</refpurpose>
</refnamediv>
<refsynopsisdiv>
@@ -66,7 +66,7 @@ FETCH [ FORWARD | BACKWARD | RELATIVE ] [ <replaceable class="PARAMETER">#</repl
<term>RELATIVE</term>
<listitem>
<para>
Noise word for SQL92 compatibility.
Same as FORWARD; provided for SQL92 compatibility.
</para>
</listitem>
</varlistentry>
@@ -247,13 +247,20 @@ WARNING: FETCH/ABSOLUTE not supported, using RELATIVE
</title>
<para>
Note that the FORWARD, BACKWARD, and ALL keywords are
A cursor to be used in backwards fetching should be declared with the
SCROLL option. In simple cases, <productname>PostgreSQL</productname>
will allow backwards fetch from cursors not declared with SCROLL, but
this behavior is best not relied on.
</para>
<para>
The FORWARD, BACKWARD, and ALL keywords are
<productname>PostgreSQL</productname> extensions.
See below for details on compatibility issues.
</para>
<para>
Updating data in a cursor is not supported by
Updating data via a cursor is not supported by
<productname>PostgreSQL</productname>,
because mapping cursor updates back to base tables is
not generally possible, as is also the case with VIEW updates.
@@ -262,8 +269,7 @@ WARNING: FETCH/ABSOLUTE not supported, using RELATIVE
</para>
<para>
Cursors may only be used inside of transactions because
the data that they store spans multiple user queries.
Cursors may only be used inside transaction blocks.
</para>
<para>
@@ -288,7 +294,7 @@ WARNING: FETCH/ABSOLUTE not supported, using RELATIVE
</title>
<para>
The following examples traverses a table using a cursor.
The following example traverses a table using a cursor.
<programlisting>
-- Set up and use a cursor: