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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. -- This message was sent by Atlassian JIRA (v6.3.4#6332)