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  1. Phoenix
  2. PHOENIX-3023

Slow performance when limit queries are executed in parallel by default

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Details

    • Bug
    • Status: Closed
    • Major
    • Resolution: Fixed
    • 4.8.0
    • 4.8.0
    • None
    • None

    Description

      After this commit, limit queries are executed in parallel which causes performance to be ~5-10x slower. Providing a serial hint fixes it though.

      After commit:

      select * from WIDE_PK order by mypk DESC limit 1; // this takes ~400ms
      
      CLIENT 1280-CHUNK 1996304 ROWS 6380181208 BYTES PARALLEL 4-WAY REVERSE FULL SCAN OVER WIDE_PK SERVER 1 ROW LIMIT CLIENT MERGE SORT CLIENT 1 ROW LIMIT
      

      Before commit:

      select * from WIDE_PK order by mypk DESC limit 1; // this takes ~40ms
      
      CLIENT 1280-CHUNK 1996304 ROWS 6380181208 BYTES SERIAL 4-WAY REVERSE FULL SCAN OVER WIDE_PK SERVER 1 ROW LIMIT CLIENT MERGE SORT CLIENT 1 ROW LIMIT
      

      Test was done on a single node machine running HBase 0.98.17. DDL used was

      CREATE TABLE WIDE_PK (MYPK CHAR(500) NOT NULL PRIMARY KEY,CF.column1 INTEGER,CF.column2 INTEGER,CF.column3 INTEGER,CF.column4 INTEGER,CF.column5 INTEGER) SALT_BUCKETS=4 with phoenix.stats.guidepost.width of 5000000
      

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            samarthjain Samarth Jain
            mujtabachohan Mujtaba Chohan
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              Updated:
              Resolved:

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