On Wed, Mar 14, 2018 at 8:58 PM, Jesper Pedersen <jesper.peder...@redhat.com> wrote: > Hi, > > Given > > -- test.sql -- > CREATE TABLE t1 ( > a integer NOT NULL, > b integer NOT NULL > ) PARTITION BY HASH (b); > CREATE TABLE t1_p00 PARTITION OF t1 FOR VALUES WITH (MODULUS 4, REMAINDER > 0); > CREATE TABLE t1_p01 PARTITION OF t1 FOR VALUES WITH (MODULUS 4, REMAINDER > 1); > CREATE TABLE t1_p02 PARTITION OF t1 FOR VALUES WITH (MODULUS 4, REMAINDER > 2); > CREATE TABLE t1_p03 PARTITION OF t1 FOR VALUES WITH (MODULUS 4, REMAINDER > 3); > INSERT INTO t1 (SELECT i, i FROM generate_series(1, 1000000) AS i); > ANALYZE; > -- test.sql -- > > Running > > EXPLAIN (ANALYZE) SELECT * FROM t1 WHERE a = 5432; > > gives > > Gather (cost=1000.00..12780.36 rows=4 width=8) (actual time=61.270..61.309 > rows=1 loops=1) > Workers Planned: 2 > Workers Launched: 2 > -> Parallel Append (cost=0.00..11779.96 rows=4 width=8) (actual > time=38.915..57.209 rows=0 loops=3) .. .. > (18 rows) > > Parallel Append's ntuples is 1, but given nloops is 3 you end up with the > slightly confusing "(actual ... *rows=0* loops=3)". >
The number of rows displayed is total_rows / loops due to which you are seeing these numbers. This behavior is the same for all parallel nodes, nothing specific to Parallel Append. -- With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com
