[TAJO-1075] unexpected join output from input of consecutive query results including 0-size tuple segment

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.9.0
• Fix Version/s: 0.9.0

Environment

9 HDFS Data Node (Tajo 1 Master + 8 Workers), OpenJDK 1.7

• Assignee: Jinhang Choi
• Reporter: Jinhang Choi
• Created: 26/Sep/14 06:23
• Updated: 14/Oct/14 07:09
• Resolved: 14/Oct/14 07:07

Description

Tajo generates unexpected join output with some input made by consecutive query execution including 0-size tuple segments. For example,

0.
external table t: 1.1GB data near 24M rows
external table u: 776KB data near 64K rows

1.
tajo query 1> create table t1 as select * from t where t.a=xxx;
tajo query 1a> create table t1_ext as select t1.*, u.b from t1 inner join u on t1.key=u.key;
tajo query 2> create table t2 as select * from t where t.a=yyy;
tajo query 2a> create table t2_ext as select t2.*, u.b from t2 inner join u on t2.key=u.key;

Table t1_ext and t2_ext are flawless (tajo succeeded in executing queries). The last output from a series of query executions has 3MB data near 64K rows in hdfs, as following:

Permission Owner Group Size Replication Block Size Name
rw-rr- hadoop supergroup 0 B 2 32 MB part-03-000000-000
rw-rr- hadoop supergroup 0 B 2 32 MB part-03-000001-000
rw-rr- hadoop supergroup 0 B 2 32 MB part-03-000002-000
rw-rr- hadoop supergroup 0 B 2 32 MB part-03-000003-000
rw-rr- hadoop supergroup 0 B 2 32 MB part-03-000004-000
rw-rr- hadoop supergroup 0 B 2 32 MB part-03-000005-000
rw-rr- hadoop supergroup 0 B 2 32 MB part-03-000006-000
rw-rr- hadoop supergroup 1.03 MB 2 32 MB part-03-000007-000
rw-rr- hadoop supergroup 1.92 MB 2 32 MB part-03-000008-000

2.
tajo query 3> select * from t1_ext inner join t2_ext on t1_ext.key=t2_ext.key;

the join query result produces abnormal output, for example, having nothing regardless of the existence of matching key.

3.
after receiving some advices from jihoonson, I manually removed 0-size tuple data in hdfs directory, and re-executed tajo query 3. The result indicates that TAJO WORKS PROPERLY.

Since not explored tajo source in depth, I can pinpoint nowhere to modify. It needs committer's support.

Issue Links

• is related to: TAJO-1101 Broadcast join with a zero-length file table returns wrong result data.