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harshit-gangal merged 1 commit into from
Feb 7, 2024
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content/en/docs/19.0: document QueryCache{Hits,Misses} stats #1663

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8 changes: 6 additions & 2 deletions content/en/docs/19.0/user-guides/configuration-basic/monitoring.md
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Expand Up @@ -278,9 +278,13 @@ There are other internal pools used by vttablet that are not very consequential.

The above three variables are table acl stats. They are broken out by table, plan and user.

#### `QueryPlanCacheSize`
#### `QueryCacheCapacity`, `QueryCacheEvictions`, `QueryCacheHits`, `QueryCacheMisses`, `QueryCacheSize`

If the application does not make good use of bind variables, this value would reach the QueryCacheCapacity. If so, inspecting the current query cache will give you a clue about where the misuse is happening.
VTTablet maintains a cache of query plans, and instruments cache usage in `QueryCache*` stats.

If the application does not make good use of bind variables, `QueryCacheSize` will reach the value of `QueryCacheCapacity`, at which point `QueryCacheEvictions` would increase. Monitoring the current `QueryCacheSize`will give you a clue about where the misuse is happening.

`QueryCacheHits` and `QueryCacheMisses` provide visibility, respectively, into how many queries are being sped up by the cache or else have to fall back to the slower path of query parsing and planning.

#### `QueryCounts`, `QueryErrorCounts`, `QueryRowCounts`, `QueryTimesNs`

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