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https://issues.apache.org/jira/browse/HAWQ-70?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15074619#comment-15074619
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Dong Li edited comment on HAWQ-70 at 12/30/15 5:07 AM:
-------------------------------------------------------
The size of data size >128*3MB , so dispatcher should start 4 QE processes to
read data, but it only starts 3 QE processes to read data , which causes it
lost 128MB data to read and count result is wrong.
The key point of this bug is to check why dispatcher only start 3 QE processes.
Next I explain the execute plan, I found it only plan 3 segments to execute.
{code}
a=# explain select count(*) from foo;
QUERY PLAN
------------------------------------------------------------------------------------
Aggregate (cost=0.00..529.00 rows=1 width=8)
-> Gather Motion 3:1 (slice1; segments: 3) (cost=0.00..529.00 rows=1
width=8)
-> Aggregate (cost=0.00..529.00 rows=1 width=8)
-> Table Scan on foo (cost=0.00..513.50 rows=8333334 width=1)
Settings: optimizer=on
Optimizer status: PQO version 1.614
(6 rows)
{code}
was (Author: doli):
The size of data size >128*3MB , so dispatcher should start 4 QE processes to
read data, but it only starts 3 QE processes to read data , which causes it
lost 128MB data to read and count result is wrong.
The key point of this bug is to check why dispatcher only start 3 QE processes.
Next I explain the execute plan, I found it only plan 3 segments to execute.
{code}
a=# explain select count(*) from foo;
QUERY PLAN
------------------------------------------------------------------------------------
Aggregate (cost=0.00..529.00 rows=1 width=8)
-> Gather Motion 3:1 (slice1; segments: 3) (cost=0.00..529.00 rows=1
width=8)
-> Aggregate (cost=0.00..529.00 rows=1 width=8)
-> Table Scan on foo (cost=0.00..513.50 rows=8333334 width=1)
Settings: optimizer=on
Optimizer status: PQO version 1.614
(6 rows)
{code}
> INSERT INTO foo SELECT * FROM foo returned successful, but the data of foo
> was not as expected.
> -----------------------------------------------------------------------------------------------
>
> Key: HAWQ-70
> URL: https://issues.apache.org/jira/browse/HAWQ-70
> Project: Apache HAWQ
> Issue Type: Bug
> Components: Query Execution
> Reporter: Lirong Jian
> Assignee: George Caragea
>
> Reproduce steps:
> postgres=# CREATE TABLE foo (a INT);
> CREATE TABLE
> postgres=# INSERT INTO foo VALUES(generate_series(1, 25000000));
> INSERT 0 25000000
> postgres=# SELECT COUNT(*) FROM foo;
> count
> ----------
> 25000000
> (1 row)
> postgres=# INSERT INTO foo SELECT * FROM foo;
> INSERT 0 25000000
> postgres=# SELECT COUNT(*) FROM foo;
> count
> ----------
> 38402176
> (1 row)
> The expected answer is 50000000.
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