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Fix handling of multiple AFTER ROW triggers on a foreign table.

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AfterTriggerExecute() retrieves a fresh tuple or pair of tuples from a
tuplestore and then stores the tuple(s) in the passed-in slot(s) if
AFTER_TRIGGER_FDW_FETCH, while it uses the most-recently-retrieved
tuple(s) stored in the slot(s) if AFTER_TRIGGER_FDW_REUSE.  This was
done correctly before 12, but commit ff11e7f4b broke it by mistakenly
clearing the tuple(s) stored in the slot(s) in that function, leading to
an assertion failure as reported in bug #16139 from Alexander Lakhin.

Also, fix some other issues with the aforementioned commit in passing:

* For tg_newslot, which is a slot added to the TriggerData struct by the
  commit to store new updated tuples, it didn't ensure the slot was NULL
  if there was no such tuple.
* The commit failed to update the documentation about the trigger
  interface.

Author: Etsuro Fujita
Backpatch-through: 12
Discussion: https://postgr.es/m/16139-94f9ccf0db6119ec%40postgresql.org
This commit is contained in:
Etsuro Fujita
2019-12-10 18:00:30 +09:00
parent 28e6a2fd63
commit 5a20b0219e
4 changed files with 81 additions and 24 deletions
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16
doc/src/sgml/trigger.sgml
View File

@ -511,8 +511,8 @@ typedef struct TriggerData
HeapTuple tg_trigtuple;
HeapTuple tg_newtuple;
Trigger *tg_trigger;
Buffer tg_trigtuplebuf;
Buffer tg_newtuplebuf;
TupleTableSlot *tg_trigslot;
TupleTableSlot *tg_newslot;
Tuplestorestate *tg_oldtable;
Tuplestorestate *tg_newtable;
} TriggerData;
@ -714,21 +714,21 @@ typedef struct Trigger
</varlistentry>
<varlistentry>
<term><structfield>tg_trigtuplebuf</structfield></term>
<term><structfield>tg_trigslot</structfield></term>
<listitem>
<para>
The buffer containing <structfield>tg_trigtuple</structfield>, or <symbol>InvalidBuffer</symbol> if there
is no such tuple or it is not stored in a disk buffer.
The slot containing <structfield>tg_trigtuple</structfield>,
or a <symbol>NULL</symbol> pointer if there is no such tuple.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><structfield>tg_newtuplebuf</structfield></term>
<term><structfield>tg_newslot</structfield></term>
<listitem>
<para>
The buffer containing <structfield>tg_newtuple</structfield>, or <symbol>InvalidBuffer</symbol> if there
is no such tuple or it is not stored in a disk buffer.
The slot containing <structfield>tg_newtuple</structfield>,
or a <symbol>NULL</symbol> pointer if there is no such tuple.
</para>
</listitem>
</varlistentry>