[DRILL-2568] New partition pruning prevents the optimization for trivial COUNT(*) queries

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.8.0
• Fix Version/s: 0.9.0
• Component/s: Query Planning & Optimization
• Assignee: Aman Sinha
• Reporter: Aman Sinha
• Created: 25/Mar/15 22:18
• Updated: 28/Mar/15 08:01
• Resolved: 28/Mar/15 08:01

Description

With the new interpreter based partition pruning, if the query has only partition filters and they are pushed into the Scan, we don't drop the Filter node from the plan. This prevents the optimization for COUNT queries against parquet files where we read the count values directly from the parquet files instead of scanning and aggregating. The ConvertCountToDirectScan rule does not get applied if there is an intervening Filter between the Scan and the Aggregate nodes.

0: jdbc:drill:zk=local> explain plan for select count(*) from dfs.`/Users/asinha/data/multilevel/parquet` where dir0=1995;
+------------+------------+
|    text    |    json    |
+------------+------------+
| 00-00    Screen
00-01      StreamAgg(group=[{}], EXPR$0=[COUNT()])
00-02        Project($f0=[0])
00-03          SelectionVectorRemover
00-04            Filter(condition=[=($0, 1995)])
00-05              Scan(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath [path=file:/Users/asinha/data/multilevel/parquet/1995/Q1/orders_95_q1.parquet], ReadEntryWithPath [path=file:/Users/asinha/data/multilevel/parquet/1995/Q2/orders_95_q2.parquet], ReadEntryWithPath [path=file:/Users/asinha/data/multilevel/parquet/1995/Q3/orders_95_q3.parquet], ReadEntryWithPath [path=file:/Users/asinha/data/multilevel/parquet/1995/Q4/orders_95_q4.parquet]], selectionRoot=/Users/asinha/data/multilevel/parquet, numFiles=4, columns=[`dir0`]]])