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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>43.8. Transaction Management</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="plpgsql-cursors.html" title="43.7. Cursors" /><link rel="next" href="plpgsql-errors-and-messages.html" title="43.9. Errors and Messages" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">43.8. Transaction Management</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="plpgsql-cursors.html" title="43.7. Cursors">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="plpgsql.html" title="Chapter 43. PL/pgSQL — SQL Procedural Language">Up</a></td><th width="60%" align="center">Chapter 43. <span class="application">PL/pgSQL</span> — <acronym class="acronym">SQL</acronym> Procedural Language</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="plpgsql-errors-and-messages.html" title="43.9. Errors and Messages">Next</a></td></tr></table><hr /></div><div class="sect1" id="PLPGSQL-TRANSACTIONS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">43.8. Transaction Management</h2></div></div></div><p>
In procedures invoked by the <code class="command">CALL</code> command
as well as in anonymous code blocks (<code class="command">DO</code> command),
it is possible to end transactions using the
commands <code class="command">COMMIT</code> and <code class="command">ROLLBACK</code>. A new
transaction is started automatically after a transaction is ended using
these commands, so there is no separate <code class="command">START
TRANSACTION</code> command. (Note that <code class="command">BEGIN</code> and
<code class="command">END</code> have different meanings in PL/pgSQL.)
</p><p>
Here is a simple example:
</p><pre class="programlisting">
CREATE PROCEDURE transaction_test1()
LANGUAGE plpgsql
AS $$
BEGIN
FOR i IN 0..9 LOOP
INSERT INTO test1 (a) VALUES (i);
IF i % 2 = 0 THEN
COMMIT;
ELSE
ROLLBACK;
END IF;
END LOOP;
END;
$$;
CALL transaction_test1();
</pre><p>
</p><a id="id-1.8.8.10.4" class="indexterm"></a><p id="PLPGSQL-TRANSACTION-CHAIN">
A new transaction starts out with default transaction characteristics such
as transaction isolation level. In cases where transactions are committed
in a loop, it might be desirable to start new transactions automatically
with the same characteristics as the previous one. The commands
<code class="command">COMMIT AND CHAIN</code> and <code class="command">ROLLBACK AND
CHAIN</code> accomplish this.
</p><p>
Transaction control is only possible in <code class="command">CALL</code> or
<code class="command">DO</code> invocations from the top level or nested
<code class="command">CALL</code> or <code class="command">DO</code> invocations without any
other intervening command. For example, if the call stack is
<code class="command">CALL proc1()</code> → <code class="command">CALL proc2()</code>
→ <code class="command">CALL proc3()</code>, then the second and third
procedures can perform transaction control actions. But if the call stack
is <code class="command">CALL proc1()</code> → <code class="command">SELECT
func2()</code> → <code class="command">CALL proc3()</code>, then the last
procedure cannot do transaction control, because of the
<code class="command">SELECT</code> in between.
</p><p>
Special considerations apply to cursor loops. Consider this example:
</p><pre class="programlisting">
CREATE PROCEDURE transaction_test2()
LANGUAGE plpgsql
AS $$
DECLARE
r RECORD;
BEGIN
FOR r IN SELECT * FROM test2 ORDER BY x LOOP
INSERT INTO test1 (a) VALUES (r.x);
COMMIT;
END LOOP;
END;
$$;
CALL transaction_test2();
</pre><p>
Normally, cursors are automatically closed at transaction commit.
However, a cursor created as part of a loop like this is automatically
converted to a holdable cursor by the first <code class="command">COMMIT</code> or
<code class="command">ROLLBACK</code>. That means that the cursor is fully
evaluated at the first <code class="command">COMMIT</code> or
<code class="command">ROLLBACK</code> rather than row by row. The cursor is still
removed automatically after the loop, so this is mostly invisible to the
user.
</p><p>
Transaction commands are not allowed in cursor loops driven by commands
that are not read-only (for example <code class="command">UPDATE
... RETURNING</code>).
</p><p>
A transaction cannot be ended inside a block with exception handlers.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="plpgsql-cursors.html" title="43.7. Cursors">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="plpgsql.html" title="Chapter 43. PL/pgSQL — SQL Procedural Language">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="plpgsql-errors-and-messages.html" title="43.9. Errors and Messages">Next</a></td></tr><tr><td width="40%" align="left" valign="top">43.7. Cursors </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 43.9. Errors and Messages</td></tr></table></div></body></html>
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