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commit    bca802600c7fe002b21991b119ec7d95ed3ebecb
Author:   Michael Paquier <michael@paquier.xyz>
Date:     Tue Oct 29 06:35:21 2024 +0000

    doc: Add better description for rewrite functions in event triggers
    
    There are two functions that can be used in event triggers to get more
    details about a rewrite happening on a relation.  Both had a limited
    documentation:
    - pg_event_trigger_table_rewrite_reason() and
    pg_event_trigger_table_rewrite_oid() were not mentioned in the main
    event trigger section in the paragraph dedicated to the event
    table_rewrite.
    - pg_event_trigger_table_rewrite_reason() returns an integer which is a
    bitmap of the reasons why a rewrite happens.  There was no explanation
    about the meaning of these values, forcing the reader to look at the
    code to find out that these are defined in event_trigger.h.
    
    While on it, let's add a comment in event_trigger.h where the
    AT_REWRITE_* are defined, telling to update the documentation when
    these values are changed.
    
    Backpatch down to 13 as a consequence of 1ad23335f36b, where this area
    of the documentation has been heavily reworked.
    
    Author: Greg Sabino Mullane
    Discussion: https://postgr.es/m/CAKAnmmL+Z6j-C8dAx1tVrnBmZJu+BSoc68WSg3sR+CVNjBCqbw@mail.gmail.com
    Backpatch-through: 13


 doc/src/sgml/event-trigger.sgml      | 5 +++++
 doc/src/sgml/func.sgml               | 8 ++++++--
 src/include/commands/event_trigger.h | 6 ++++++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/event-trigger.sgml b/doc/src/sgml/event-trigger.sgml
index a76e8ac09be..8cf4691fa41 100644
--- a/doc/src/sgml/event-trigger.sgml
+++ b/doc/src/sgml/event-trigger.sgml
@@ -80,6 +80,11 @@
     control statements are available to rewrite a table,
     like <literal>CLUSTER</literal> and <literal>VACUUM</literal>,
     the <literal>table_rewrite</literal> event is not triggered by them.
+    To find the OID of the table that was rewritten, use the function
+    <literal>pg_event_trigger_table_rewrite_oid()</literal> (see
+    <xref linkend="functions-event-triggers"/>). To discover the reason(s)
+    for the rewrite, use the function
+    <literal>pg_event_trigger_table_rewrite_reason()</literal>.
    </para>
 
    <para>
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 6ee09fc288a..2f95d5a2b58 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -27783,8 +27783,12 @@ CREATE EVENT TRIGGER test_event_trigger_for_drops
         <returnvalue>integer</returnvalue>
        </para>
        <para>
-        Returns a code explaining the reason(s) for rewriting.  The exact
-        meaning of the codes is release dependent.
+        Returns a code explaining the reason(s) for rewriting. The value is
+        a bitmap built from the following values: <literal>1</literal>
+        (the table has changed its persistence), <literal>2</literal>
+        (default value of a column has changed), <literal>4</literal>
+        (a column has a new data type) and <literal>8</literal>
+        (the table access method has changed).
        </para></entry>
       </row>
      </tbody>
diff --git a/src/include/commands/event_trigger.h b/src/include/commands/event_trigger.h
index c11bf2d7810..9338b7a2777 100644
--- a/src/include/commands/event_trigger.h
+++ b/src/include/commands/event_trigger.h
@@ -29,6 +29,12 @@ typedef struct EventTriggerData
 	CommandTag	tag;
 } EventTriggerData;
 
+/*
+ * Reasons for relation rewrites.
+ *
+ * pg_event_trigger_table_rewrite_reason() uses these values, so make sure to
+ * update the documentation when changing this list.
+ */
 #define AT_REWRITE_ALTER_PERSISTENCE	0x01
 #define AT_REWRITE_DEFAULT_VAL			0x02
 #define AT_REWRITE_COLUMN_REWRITE		0x04


[parent: ca643bcd7a81]