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From:Michael Widenius Date:September 7 1999 3:46pm
Subject:Why are these INSERT DELAYEDs blocking?
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>>>>> "Jules" == Jules Bean <jules@stripped> writes:

Jules> Attached is the output of show processlist (mangled to protect my
Jules> client's private data).  I haven't included it in the body of the email,
Jules> since it is far wider that 80 characters..

Jules> I can understand that thread 5875 (INSERT DELAYED INTO tab_b) is blocked
Jules> because of the pending ALTER TABLE (thread 5841).

Jules> But what is not clear to me is why all the INSERT DELAYED INTO tab_a are
Jules> waiting (look at the time column) although there is to tab_a access
Jules> going on.

Jules> Does one DELAYED lock lock all tables?  This isn't the impression I got
Jules> from the manual page...

Jules> (the flush tables is a red herring - I started that, as you can tell
Jules> from the timestamps, after the situation had become apparent).

Jules> This is mysql  Ver 9.32 Distrib 3.22.23b, for pc-linux-gnu (i586)

<cut>

Hi!

I checked the code and the problem is that we have a large lock
around the creating of a 'delayed insert thread'; This means that you
can't create a new insert delayed handler as long as another one is
created.  The problem in this case is that a handler on 'tab_b' can't
be created until the ALTER TABLE on 'tab_b' is ready and the handler
on tab_a can't be create until tab_b is ready.

I shall try to fix this by the end of this week.  Sorry for the delay...

Regards,
Monty
Thread
Why are these INSERT DELAYEDs blocking?Jules Bean3 Sep
  • Why are these INSERT DELAYEDs blocking?Michael Widenius8 Sep
  • Re: Why are these INSERT DELAYEDs blocking?Jules Bean8 Sep