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1 | 1 | <!--
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2 |
| -$PostgreSQL: pgsql/doc/src/sgml/trigger.sgml,v 1.35 2004/03/03 22:22:24 neilc Exp $ |
| 2 | +$PostgreSQL: pgsql/doc/src/sgml/trigger.sgml,v 1.36 2004/08/13 16:17:19 tgl Exp $ |
3 | 3 | -->
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4 | 4 |
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5 | 5 | <chapter id="triggers">
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@@ -431,8 +431,10 @@ typedef struct Trigger
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431 | 431 | </para>
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432 | 432 |
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433 | 433 | <para>
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434 |
| - A trigger function must return either <symbol>NULL</> or a |
435 |
| - <structname>HeapTuple</> pointer. Be careful to return either |
| 434 | + A trigger function must return either a |
| 435 | + <structname>HeapTuple</> pointer or a <symbol>NULL</> pointer |
| 436 | + (<emphasis>not</> a SQL NULL, that is, do not set isNull true). |
| 437 | + Be careful to return either |
436 | 438 | <structfield>tg_trigtuple</> or <structfield>tg_newtuple</>,
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437 | 439 | as appropriate, if you don't want to modify the row being operated on.
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438 | 440 | </para>
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