[jira] [Created] (DRILL-7418) MetadataDirectGroupScan improvements

["Arina Ielchiieva (Jira)" <ji...@apache.org>]

Arina Ielchiieva created DRILL-7418:
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             Summary: MetadataDirectGroupScan improvements
                 Key: DRILL-7418
                 URL: https://issues.apache.org/jira/browse/DRILL-7418
             Project: Apache Drill
          Issue Type: Improvement
    Affects Versions: 1.16.0
            Reporter: Arina Ielchiieva
            Assignee: Arina Ielchiieva
             Fix For: 1.17.0


When count is converted to direct scan (case when statistics and table metadata are available and there is no need to perform count operation), {{MetadataDirectGroupScan}} is used. Proposed {{MetadataDirectGroupScan}} enhancements:
1. show table root instead listing all table files. If users= has lots of files, query plan gets polluted with files enumeration. Since files are not used for calculation (only metadata), they are not relevant and can be excluded from plan.

Before:
{noformat}
| 00-00    Screen
00-01      Project(EXPR$0=[$0], EXPR$1=[$1], EXPR$2=[$2], EXPR$3=[$3])
00-02        DirectScan(groupscan=[files = [/drill/testdata/metadata_cache/store_sales_null_blocks_all/0_0_0.parquet, /drill/testdata/metadata_cache/store_sales_null_blocks_all/0_0_5.parquet, /drill/testdata/metadata_cache/store_sales_null_blocks_all/0_0_4.parquet, /drill/testdata/metadata_cache/store_sales_null_blocks_all/0_0_9.parquet, /drill/testdata/metadata_cache/store_sales_null_blocks_all/0_0_3.parquet, /drill/testdata/metadata_cache/store_sales_null_blocks_all/0_0_6.parquet, /drill/testdata/metadata_cache/store_sales_null_blocks_all/0_0_7.parquet, /drill/testdata/metadata_cache/store_sales_null_blocks_all/0_0_10.parquet, /drill/testdata/metadata_cache/store_sales_null_blocks_all/0_0_2.parquet, /drill/testdata/metadata_cache/store_sales_null_blocks_all/0_0_1.parquet, /drill/testdata/metadata_cache/store_sales_null_blocks_all/0_0_8.parquet], numFiles = 11, usedMetadataSummaryFile = false, DynamicPojoRecordReader{records = [[1560060, 2880404, 2880404, 0]]}])
{noformat}


After:
{noformat}
| 00-00    Screen
00-01      Project(EXPR$0=[$0], EXPR$1=[$1], EXPR$2=[$2], EXPR$3=[$3])
00-02        DirectScan(groupscan=[selectionRoot = /drill/testdata/metadata_cache/store_sales_null_blocks_all, numFiles = 11, 
usedMetadataSummaryFile = false, DynamicPojoRecordReader{records = [[1560060, 2880404, 2880404, 0]]}])
{noformat}

2. Submission of physical plan which contains {{MetadataDirectGroupScan}} fails with deserialization errors, proper ser / de should be implemented.



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