Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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10.1(EOL), 10.2(EOL), 10.3(EOL), 10.4(EOL), 10.5
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None
Description
void TABLE::initialize_quick_structures()
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{
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bzero(quick_rows, sizeof(quick_rows));
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bzero(quick_key_parts, sizeof(quick_key_parts));
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bzero(quick_costs, sizeof(quick_costs));
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bzero(quick_n_ranges, sizeof(quick_n_ranges));
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}
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1. These members consume 1536 of 3520 bytes (44%) of TABLE for no good reason.
2. I doubt these arrays have to be fully initialized. I'd say they have to be initialized up to the number of indexes in the table.
3. Assuming these are per-key variables, they should be part of something like KEY rather than something like TABLE.
4. I generally recommend not using pre-initialization for performance reasons, but also because it tends to hide bugs from uninit-var detectors.
Attachments
Issue Links
- is caused by
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- Closed
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Activity
Patch
https://github.com/MariaDB/server/commit/e005f4db78c3fd08a33c87e2bcb8b6055e929ed9
The patch currently just moves the initialisation from TABLE::init to test_quick_select where we run the range optimizer.
I am working on a fix for this in 10.6; Let see how it looks when I am done if we should backport it to earlier versions.
Fix for 10.5 done and tested.
Have done a simpler and safer fix for 10.3. However to be able to push this, I need first to get 10.3 working with valgrind.
Working now on 10.3 and valgrind
Testing, merging, testing etc (Lot's of valgrind run's to verify that the change is safe)
10.3 & 10.4 fixed by not doing the initialization at all.
In 10.5 I do separate allocation for the table->quick items and instead of allocation MAX_KEY items,
we now only allocate as much space as we need. This made the TABLE structure much smaller,
(3528 -> 984 + keyinfo), which should save space and increase performance.
@Monty suggested to remove the initialisation and always check first if quick_keys is set only then use the quick
structures array. He requested to change the initialisation to undefined memory under valgrind