[jira] [Commented] (HIVE-25074) Remove Metastore flushCache usage

["Kishen Das (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-25074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17342181#comment-17342181 ] 

Kishen Das commented on HIVE-25074:
-----------------------------------

[~pvary] I don't see any usage of this API in Impala. 

> Remove Metastore flushCache usage
> ---------------------------------
>
>                 Key: HIVE-25074
>                 URL: https://issues.apache.org/jira/browse/HIVE-25074
>             Project: Hive
>          Issue Type: Improvement
>          Components: Metastore, Standalone Metastore
>    Affects Versions: 4.0.0
>            Reporter: Miklos Szurap
>            Assignee: Zoltan Chovan
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> The "flushCache" in HiveMetaStore with the ObjectStore implementation is currently a NOOP:
> {code:java}
>   public void flushCache() {
>     // NOP as there's no caching
>   } {code}
> The HBaseStore (HBaseReadWrite) had some logic in it, however it has been removed in HIVE-17234.
> As I see the calls are going like this:
> HiveMetaStoreClient.flushCache() -> CachedStore.flushCache() -> ObjectStore.flushCache()
> There are significant amount of calls (about 10% of all calls) made from the client to the server - to do nothing. We could spare the call to the server completely, including getting a DB connection which can take 1+ seconds under high load scenarios slowing down Hive queries unnecessarily.
> Can we:
>  # Deprecate the RawStore.flushCache (if there are other implementations)
>  # Deprecate the HiveMetaStoreClient.flushCache()
>  # Do the NOOP on the client side in HiveMetaStoreClient.flushCache() (while it is not removed in a next version)



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