I hava below two statement sql: 0. not in subquery select a.schemaname, pg_size_pretty(pg_total_relation_size(a.schemaname||'.'||a.tablename)) from pg_tables a where a.tablename not in (select b.tablename from t b); 1. in subquery select a.schemaname, pg_size_pretty(pg_total_relation_size(a.schemaname||'.'||a.tablename)) from pg_tables a where a.tablename in (select b.tablename from t b); The [0. not in subquery] can't work well, it's occur error: ERROR: query plan with multiple segworker groups is not supported (cdbdisp.c:500) HINT: likely caused by a function that reads or modifies data in a distributed table CONTEXT: SQL statement "select sum(pg_total_relation_size('information_schema.sql_languages'))::int8 from gp_dist_random('gp_id');" The [1. in subquery] work well. Detailed below test:

gtlions=# select version();version------------------------------------------------------------------------------------------------------------------------------------------------------PostgreSQL 8.2.15 (Greenplum Database 4.2.7.3 build 1) on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.4.2 compiled on May 7 2014 14:31:08(1 row)gtlions=# select a.schemaname, pg_size_pretty(pg_total_relation_size(a.schemaname||'.'||a.tablename)) from pg_tables a where a.tablename not in (select b.tablename from t b);ERROR: query plan with multiple segworker groups is not supported (cdbdisp.c:500)HINT: likely caused by a function that reads or modifies data in a distributed tableCONTEXT: SQL statement "select sum(pg_total_relation_size('information_schema.sql_languages'))::int8 from gp_dist_random('gp_id');"gtlions=# explain select a.schemaname, pg_size_pretty(pg_total_relation_size(a.schemaname||'.'||a.tablename)) from pg_tables a where a.tablename not in (select b.tablename from t b);QUERY PLAN-----------------------------------------------------------------------------------------------Hash Left Anti Semi Join (cost=568.98..235912.69 rows=676396 width=128)Hash Cond: c.relname = "NotIn_SUBQUERY".tablename::name-> Hash Left Join (cost=395.97..223194.68 rows=676419 width=128)Hash Cond: c.relnamespace = n.oid-> Hash Left Join (cost=2.62..112777.67 rows=676419 width=68)Hash Cond: c.reltablespace = t.oid-> Seq Scan on pg_class c (cost=0.00..2751.39 rows=676419 width=72)Filter: relkind = 'r'::"char" AND relname IS NOT NULL-> Hash (cost=1.02..1.02 rows=2 width=4)-> Seq Scan on pg_tablespace t (cost=0.00..1.02 rows=128 width=4)-> Hash (cost=365.35..365.35 rows=35 width=68)-> Seq Scan on pg_namespace n (cost=0.00..365.35 rows=2240 width=68)-> Hash (cost=106.61..106.61 rows=83 width=274)-> Gather Motion 64:1 (slice1; segments: 64) (cost=0.00..106.61 rows=83 width=274)-> Subquery Scan "NotIn_SUBQUERY" (cost=0.00..52.66 rows=2 width=274)-> Seq Scan on t b (cost=0.00..51.83 rows=2 width=24)(16 rows)gtlions=# select a.schemaname, pg_size_pretty(pg_total_relation_size(a.schemaname||'.'||a.tablename)) from pg_tables a where a.tablename in (select b.tablename from t b);schemaname | size-1-------------+---------public | 32 kBpublic | 32 kB............public | 96 kBgtlions=# explain select a.schemaname, pg_size_pretty(pg_total_relation_size(a.schemaname||'.'||a.tablename)) from pg_tables a where a.tablename in (select b.tablename from t b);QUERY PLAN---------------------------------------------------------------------------------------------------------------------------------Gather Motion 64:1 (slice7; segments: 64) (cost=445.41..10096.03 rows=1 width=128)-> Hash Left Join (cost=445.41..10096.03 rows=1 width=128)Hash Cond: c.reltablespace = t.oid-> Redistribute Motion 64:64 (slice5; segments: 64) (cost=443.06..10092.81 rows=1 width=132)Hash Key: c.reltablespace-> Hash Left Join (cost=443.06..10092.22 rows=1 width=132)Hash Cond: c.relnamespace = n.oid-> Redistribute Motion 64:64 (slice3; segments: 64) (cost=54.53..9703.24 rows=1 width=72)Hash Key: c.relnamespace-> Hash EXISTS Join (cost=54.53..9702.65 rows=1 width=72)Hash Cond: c.relname = b.tablename::name-> Redistribute Motion 1:64 (slice1) (cost=0.00..9621.26 rows=10570 width=72)Hash Key: c.relname-> Seq Scan on pg_class c (cost=0.00..2751.39 rows=676419 width=72)Filter: relkind = 'r'::"char"-> Hash (cost=53.49..53.49 rows=2 width=24)-> Redistribute Motion 64:64 (slice2; segments: 64) (cost=0.00..53.49 rows=2 width=24)Hash Key: b.tablename::name-> Seq Scan on t b (cost=0.00..51.83 rows=2 width=24)-> Hash (cost=388.10..388.10 rows=1 width=68)-> Redistribute Motion 1:64 (slice4) (cost=0.00..388.10 rows=35 width=68)Hash Key: n.oid-> Seq Scan on pg_namespace n (cost=0.00..365.35 rows=2240 width=68)-> Hash (cost=2.32..2.32 rows=1 width=4)-> Redistribute Motion 1:64 (slice6) (cost=0.00..2.32 rows=2 width=4)Hash Key: t.oid-> Seq Scan on pg_tablespace t (cost=0.00..1.02 rows=128 width=4)(27 rows)

    该问题应该是个Bug,等一下TSE鉴于Fix或不Fix而只是等待，直到下一个版本升级. -EOF-