ER_MAX_PREPARED_STMT_COUNT_REACHED in batch inserts

[webigorkiev]

Hello

mariadb@3.0.1

When i use batch inserts or pool.batch
growing
Com_stmt_prepare
but
Com_stmt_close = 0

And then i get ER_MAX_PREPARED_STMT_COUNT_REACHED error

mariadb@2.5.6

This does not appear

Thanks

[webigorkiev]

Workaround

prepareCacheLength: 0

[rusher]

found the issue. Problem reside in prepare cache that doesn't execute close immediatly, resulting in having more cached prepare than prepareCacheLength

[rusher]

Current implementation use @alloc/quick-lru that evict previous cache by bulk. Cache maximum option prepareCacheLength is then not repected, because can be up to 2x that value, leading to error when reaching server max_prepared_stmt_count. After implementation verification and benchmarking, lru-cache will be the replacement, resolving the issue in next version