我有下面两条语句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.来自 t b) 的表名； 1. 在子查询中选择a.
我有下面两条语句sql：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 table CONTEXT: 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 kB public | 32 kB ...... ...... public | 96 kB gtlions=# 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)
