Do not acquire lock for total_bytes/total_rows for Buffer engine #24066
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robot-clickhouse
added
the
pr-improvement
When Buffer() is under preassure, acquiring per-layer lock may take
significant time. And so the following query may take significant amount of time:
SELECT total_bytes, total_rows FROM system.tables WHERE engine='Buffer'
azat
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kitaisreal
approved these changes
May 13, 2021
azat
commented
May 24, 2021
| @@ -606,6 +606,9 @@ class BufferBlockOutputStream : public IBlockOutputStream | |||
| if (!buffer.data) | |||
| { | |||
| buffer.data = sorted_block.cloneEmpty(); | |||
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| storage.total_writes.rows += buffer.data.rows(); | |||
| storage.total_writes.bytes += buffer.data.allocatedBytes(); | |||
azat
commented
May 24, 2021
Comment on lines
+626
to
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| size_t old_rows = buffer.data.rows(); | ||
| size_t old_bytes = buffer.data.allocatedBytes(); | ||
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| appendBlock(sorted_block, buffer.data); | ||
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| storage.total_writes.rows += (buffer.data.rows() - old_rows); | ||
| storage.total_writes.bytes += (buffer.data.allocatedBytes() - old_bytes); |
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Looks like it is better to check this for overflow
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Changelog category (leave one):
Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):
Do not acquire lock for total_bytes/total_rows for Buffer engine
Detailed description / Documentation draft:
When Buffer() is under preassure, acquiring per-layer lock may take
significant time. And so the following query may take significant amount of time: