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Offer triggers on foreign tables.

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This covers all the SQL-standard trigger types supported for regular
tables; it does not cover constraint triggers.  The approach for
acquiring the old row mirrors that for view INSTEAD OF triggers.  For
AFTER ROW triggers, we spool the foreign tuples to a tuplestore.

This changes the FDW API contract; when deciding which columns to
populate in the slot returned from data modification callbacks, writable
FDWs will need to check for AFTER ROW triggers in addition to checking
for a RETURNING clause.

In support of the feature addition, refactor the TriggerFlags bits and
the assembly of old tuples in ModifyTable.

Ronan Dunklau, reviewed by KaiGai Kohei; some additional hacking by me.
This commit is contained in:
Noah Misch
2014-03-23 02:16:34 -04:00
parent 6115480c54
commit 7cbe57c34d
14 changed files with 1145 additions and 202 deletions
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25
doc/src/sgml/trigger.sgml
View File

@@ -33,20 +33,21 @@
<para>
A trigger is a specification that the database should automatically
execute a particular function whenever a certain type of operation is
performed. Triggers can be attached to both tables and views.
performed. Triggers can be attached to tables, views, and foreign tables.
</para>
<para>
On tables, triggers can be defined to execute either before or after any
<command>INSERT</command>, <command>UPDATE</command>, or
<command>DELETE</command> operation, either once per modified row,
On tables and foreign tables, triggers can be defined to execute either
before or after any <command>INSERT</command>, <command>UPDATE</command>,
or <command>DELETE</command> operation, either once per modified row,
or once per <acronym>SQL</acronym> statement.
<command>UPDATE</command> triggers can moreover be set to fire only if
certain columns are mentioned in the <literal>SET</literal> clause of the
<command>UPDATE</command> statement.
Triggers can also fire for <command>TRUNCATE</command> statements.
If a trigger event occurs, the trigger's function is called at the
appropriate time to handle the event.
appropriate time to handle the event. Foreign tables do not support the
TRUNCATE statement at all.
</para>
<para>
@@ -111,10 +112,10 @@
triggers fire immediately before a particular row is operated on,
while row-level <literal>AFTER</> triggers fire at the end of the
statement (but before any statement-level <literal>AFTER</> triggers).
These types of triggers may only be defined on tables. Row-level
<literal>INSTEAD OF</> triggers may only be defined on views, and fire
immediately as each row in the view is identified as needing to be
operated on.
These types of triggers may only be defined on tables and foreign tables.
Row-level <literal>INSTEAD OF</> triggers may only be defined on views,
and fire immediately as each row in the view is identified as needing to
be operated on.
</para>
<para>
@@ -548,7 +549,8 @@ typedef struct TriggerData
<command>DELETE</command> then this is what you should return
from the function if you don't want to replace the row with
a different one (in the case of <command>INSERT</command>) or
skip the operation.
skip the operation. For triggers on foreign tables, values of system
columns herein are unspecified.
</para>
</listitem>
</varlistentry>
@@ -563,7 +565,8 @@ typedef struct TriggerData
<command>DELETE</command>. This is what you have to return
from the function if the event is an <command>UPDATE</command>
and you don't want to replace this row by a different one or
skip the operation.
skip the operation. For triggers on foreign tables, values of system
columns herein are unspecified.
</para>
</listitem>
</varlistentry>