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From:Hugo van der Sanden Date:September 2 1999 12:16pm
Subject:Re: Rematch of modified record in update
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In <14272.14293.779425.635005@stripped>, Michael Widenius writes:
Hugo> Were that the case, I would have expected the same to happen in my
Hugo> test table with one record. However, it is not how I understand the SQL
Hugo> should work: regardless of implementation, I would expect the effect to
Hugo> be the same as if the where clause were first applied to find the set
Hugo> of matching records, and then the update clause applied (once!) to each
Hugo> member of the matching set.

Hugo> I suspect the fact that I am updating one field of a multi-field key is
Hugo> part of the reason for the problem.

Monty>Yes, this explain this case (This is fixed in 3.23.2)

I've finally managed to get 3.23.2 installed here, and confirmed that
the update works correctly with that version. Is there any prospect that
the relevant patches will make it into a 3.22 release at some point in
the near future? If not, I'd appreciate being pointed at the patches
so I can attempt to retrofit them myself.

As well as the reluctance to touch software marked 'alpha', the person
who installed 3.23.2 on a test machine here also thought to check the
benchmarks comparing 3.22.25 and 3.23.2, and while most operations are
as fast or faster, there are a couple of worrying anomalies:

Benchmark DBD suite: 2.2

Running tests on:    SunOS 5.7 sun4u

alpha:  Server version:      MySQL 3.23.2 alpha
stable: Server version:      MySQL 3.22.25
[...]
alpha:  All 8 test executed successfully
stable: All 8 test executed successfully

Tests with estimated time have a + at end of line

Totals per operation:
        Operation             seconds     usr     sys     cpu   tests
[...]
alpha:  select_key              91476  123.29   53.27    0.00  200000 +
stable: select_key                300  138.33   56.57    0.00  200000 
alpha:  select_range             1945   38.02   30.16    0.00   25410 +
stable: select_range              509   36.60   24.98    0.00   25420 
alpha:  select_range_prefix      9551   13.44    7.20    0.00   25000 +
stable: select_range_prefix        60   13.01    6.58    0.00   25010 
[...]
alpha:  TOTALS                 111222  747.01  569.89    0.00 1511298 ++++
stable: TOTALS                  10908  781.22  489.97    0.00 1511318 +

Hugo van der Sanden
Thread
Rematch of modified record in updatehugo18 Aug
  • Rematch of modified record in updatesinisa18 Aug
    • Re: Rematch of modified record in updateHugo van der Sanden18 Aug
      • Re: Rematch of modified record in updateMichael Widenius23 Aug
        • Re: Rematch of modified record in updateHugo van der Sanden23 Aug
        • Re: Rematch of modified record in updateHugo van der Sanden2 Sep
          • Re: Rematch of modified record in updateMichael Widenius2 Sep
            • Re: Rematch of modified record in updateHugo van der Sanden3 Sep
              • Re: Rematch of modified record in updateMichael Widenius7 Sep
  • Rematch of modified record in updateMichael Widenius23 Aug