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https://issues.apache.org/jira/browse/CALCITE-7666?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18098780#comment-18098780
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Yu Xu commented on CALCITE-7666:
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Furthermore, changing this to `static` is safe from a data perspective for the
following reasons:
1. The cached content is immutable and thread-safe: `Pattern` is an immutable
object from the Java standard library; its internal state remains unchanged
after compilation, making it safe for concurrent access by multiple threads.
2. Guava's `LoadingCache` is inherently thread-safe: operations such as
reading, automatic loading, and eviction utilize built-in synchronization
mechanisms.
3. No instance state is involved: The `CacheLoader` relies solely on the key's
fields (`pattern`, `escape`, `flags`) and is completely independent of the
`LikeFunction` instance's state.
> Make regex pattern caches static to avoid repeated allocation in
> RexInterpreter
> -------------------------------------------------------------------------------
>
> Key: CALCITE-7666
> URL: https://issues.apache.org/jira/browse/CALCITE-7666
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.42.0
> Reporter: Yu Xu
> Assignee: Yu Xu
> Priority: Minor
> Fix For: 1.43.0
>
>
> Recently, during a performance test of Simpifly, I discovered a memory
> performance issue:
> {code:java}
> SELECT * FROM t
> WHERE v0 AND (v0 OR v1 OR v2 OR ... OR v9) -- 10 boolean expression
> AND (i0 = 0 OR i0 = 1 OR i0 = 2 OR i0 = 3) -- 10 integer expression
> AND (s0 = 'foo' OR s0 = 'bar') -- 1 string expression
> {code}
> Tests of this kind generally cannot complete successfully because the data
> volume is massive: 2^10 (Boolean) × 4^10 (Integer) × 2^1 (String) =
> 21,233,664 combinations
> Based on this test, I analyzed the memory status of the process:
> It is primarily caused by the following caches:
> SqlFunctions.LikeFunction
> SqlFunctions.SimilarFunction
>
> SqlFunctions.SimilarEscapeFunction
>
> {code:java}
> private final LoadingCache<Key, Pattern> cache =
> CacheBuilder.newBuilder()
> .maximumSize(FUNCTION_LEVEL_CACHE_MAX_SIZE.value())
> .build(CacheLoader.from(Key::toPattern)); {code}
> When tests frequently call `new RexInterpreter()`, a new `LikeFunction()` or
> `SimilarFunction()` is instantiated each time, and each of these
> constructors, in turn, creates a separate Guava `LoadingCache`.
> When optimized the cache to be static, memory overhead was significantly
> reduced.The comparison results are as follows:
> ||metrics ||current||after change||ratio||
> |LocalCache instance|134,586|0|↓100%|
> |Memory usage|677M |285M|↓58%|
> |Memory compression|259M|36M|↓86%|
>
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