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From: Michael Paquier <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: Re: SQL function which allows to distinguish a server being in point in time recovery mode and an ordinary replica
Date: Fri, 14 Jun 2024 13:51:17 +0900
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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On Thu, Jun 13, 2024 at 09:07:42PM +0300, [email protected] wrote:
> Hi!
> 
> Michael,
> I have fixed the patches according to your comments.
> 
> > merge both local variables into a single bits32 store?
> This is done in v3-0001-Standby-mode-requested.patch
> 
> > Then this could be used with a function that returns a
> > text[] array with all the states retrieved?
> Placed this in the v3-0002-Text-array-sql-wrapper.patch
> 
> > The refactoring pieces and the function pieces should be split, for
> > clarity.
> Sure. I also added the third patch with some tests. Perhaps it would be
> usefull.

+     *    --    XLR_PROMOTE_IS_TRIGGERED indicates if a standby promotion
+     *        has been triggered. Protected by info_lck.
+     *
+     *     --    XLR_STANDBY_MODE_REQUESTED indicates if we're in a standby mode
+     *        at start, while recovery mode is on. No info_lck protection.
+     *
+     *    and can be extended in future.

This comment is incorrect for XLR_STANDBY_MODE_REQUESTED?  A startup
we would unlikely be in standby mode, most likely in crash recovery,
then switch to standby mode.

-    LocalPromoteIsTriggered = XLogRecoveryCtl->SharedPromoteIsTriggered;
+    LocalRecoveryDataFlags &= ~XLR_PROMOTE_IS_TRIGGERED;
+    LocalRecoveryDataFlags |=
+        (XLogRecoveryCtl->SharedRecoveryDataFlags & XLR_PROMOTE_IS_TRIGGERED)

Are these complications really needed?  All these flags are false,
then switched to true.  true -> false is not possible.

         StandbyModeRequested = true;
         ArchiveRecoveryRequested = true;
+        XLogRecoveryCtl->SharedRecoveryDataFlags |= XLR_STANDBY_MODE_REQUESTED;

Shouldn't STANDBY_MODE be only used in the local flag, as well as an
ARCHIVE_RECOVERY_REQUESTED?  It looks like this could push a bit more
forward the removal of more of these booleans, with a bit more work..

     return (LocalRecoveryDataFlags & XLR_HOT_STANDBY_ACTIVE);
 }
 
+
 /*
Some noise lying around.

+	/* Returns bit array as Datum */
+	txt_arr = construct_array_builtin(flags, cnt, TEXTOID);

Yep, that's the correct way to do it.

+is($ret_mode_primary, '{}', "master is not a replica"); 

The test additions are welcome.  Note that we avoid the word "master",
see 229f8c219f8f.
--
Michael


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