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Posted to issues@impala.apache.org by "Tim Armstrong (JIRA)" <ji...@apache.org> on 2019/07/30 01:10:00 UTC
[jira] [Resolved] (IMPALA-8807) OPTIMIZE_PARTITION_KEY_SCANS works
in more cases than documented
[ https://issues.apache.org/jira/browse/IMPALA-8807?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Tim Armstrong resolved IMPALA-8807.
-----------------------------------
Resolution: Fixed
Fix Version/s: Impala 3.3.0
> OPTIMIZE_PARTITION_KEY_SCANS works in more cases than documented
> ----------------------------------------------------------------
>
> Key: IMPALA-8807
> URL: https://issues.apache.org/jira/browse/IMPALA-8807
> Project: IMPALA
> Issue Type: Bug
> Components: Docs
> Reporter: Tim Armstrong
> Assignee: Tim Armstrong
> Priority: Major
> Labels: docs
> Fix For: Impala 3.3.0
>
>
> This came up here https://community.cloudera.com/t5/Support-Questions/Avoiding-hdfs-scan-when-querying-only-partition-columns/m-p/93337#M57192%3Feid=1&aid=1
> Our docs say
> {quote}
> This optimization does not apply if the queries contain any WHERE, GROUP BY, or HAVING clause. The relevant queries should only compute the minimum, maximum, or number of distinct values for the partition key columns across the whole table.
> {quote}
> This is false. Here's query illustrating it working with all three things:
> {noformat}
> [localhost:21000] default> set optimize_partition_key_scans=true; explain select max(ss_sold_date_sk) from tpcds_parquet.store_sales where ss_sold_date_sk % 10 = 0 group by ss_sold_date_sk having max(ss_sold_date_sk) > 1000;
> OPTIMIZE_PARTITION_KEY_SCANS set to true
> Query: explain select max(ss_sold_date_sk) from tpcds_parquet.store_sales where ss_sold_date_sk % 10 = 0 group by ss_sold_date_sk having max(ss_sold_date_sk) > 1000
> +------------------------------------------------------------+
> | Explain String |
> +------------------------------------------------------------+
> | Max Per-Host Resource Reservation: Memory=1.94MB Threads=1 |
> | Per-Host Resource Estimates: Memory=10MB |
> | Codegen disabled by planner |
> | |
> | PLAN-ROOT SINK |
> | | |
> | 01:AGGREGATE [FINALIZE] |
> | | output: max(ss_sold_date_sk) |
> | | group by: ss_sold_date_sk |
> | | having: max(ss_sold_date_sk) > 1000 |
> | | row-size=8B cardinality=182 |
> | | |
> | 00:UNION |
> | constant-operands=182 |
> | row-size=4B cardinality=182 |
> +------------------------------------------------------------+
> Fetched 15 row(s) in 0.11s
> {noformat}
> We should reword this to be correct.
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