[jira] [Commented] (HIVE-14496) Enable Calcite rewriting with materialized views

["Ashutosh Chauhan (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-14496?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15637272#comment-15637272 ] 

Ashutosh Chauhan commented on HIVE-14496:
-----------------------------------------

Few high level questions based on browsing of patch:

* I am not sure seprating view info in a seperate table is a good idea. This will result in a join between these two tables for every getTable() call, which will be perf hit. We know that denormalized schemas are good for perf :) Also this makes upgrade process little fragile since data needs to be rewritten for these tables.
* Not sure if there is a need for creation time in view key. Can you explain how it is used. Using time in distributed systems is fraught with peril.
* In view matching rule currently it has Proj-FIL-TS. If all columns are projected out, Proj may be absent. Will this rule have trouble matching that? What if there is no filter, but only TS-Proj. Will this match that?
* It seems like we are only using mv present in current db, but Hive allows user to use tables in other dbs in a single session. 
* Also I don't see any index on materializations to do early discard based on table or columns referenced. Is that part of rule itself?

> Enable Calcite rewriting with materialized views
> ------------------------------------------------
>
>                 Key: HIVE-14496
>                 URL: https://issues.apache.org/jira/browse/HIVE-14496
>             Project: Hive
>          Issue Type: Sub-task
>          Components: Materialized views
>    Affects Versions: 2.2.0
>            Reporter: Jesus Camacho Rodriguez
>            Assignee: Jesus Camacho Rodriguez
>         Attachments: HIVE-14496.01.patch, HIVE-14496.02.patch, HIVE-14496.patch
>
>
> Calcite already supports query rewriting using materialized views. We will use it to support this feature in Hive.
> In order to do that, we need to register the existing materialized views with Calcite view service and enable the materialized views rewriting rules. 
> We should include a HiveConf flag to completely disable query rewriting using materialized views if necessary.



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