Trafodion 查看执行计划
Trafodion数据库一般通过EXPLAIN命令查看SQL的执行计划，部分使用方法如下，
- explain select ... from ...;
- explain options 'f' select ... from ...;
- prepare s from select .. from ...; explain {options 'f'} s;
下面通过一个简单的两表关联介绍如何用上述几种方法分别去查看SQL的执行计划。
1 创建测试表并插入样例数据
SQL>create table test1(a int not null, b varchar(10));
--- SQL operation complete.
SQL>create table test2(a int not null, b varchar(10));
--- SQL operation complete.
SQL>insert into test1 values(1,'LIU'),(2,'WANG');
--- 2 row(s) inserted.
SQL>insert into test2 values(1,'ZHANG'),(2,'LI');
--- 2 row(s) inserted.2 explain + sql 查看执行计划
SQL>explain
+>select test1.a, test1.b, test2.b
+>from test1, test2
+>where test1.a = test2.a;
------------------------------------------------------------------ PLAN SUMMARY
MODULE_NAME .............. DYNAMICALLY COMPILED
STATEMENT_NAME ........... NOT NAMED
PLAN_ID .................. 212344925683685481
ROWS_OUT ............. 5,000
EST_TOTAL_COST ........... 0.01
STATEMENT ................
select test1.a, test1.b, test2.b
from test1,
test2
where test1.a = test2.a;
------------------------------------------------------------------ NODE LISTING
ROOT ====================================== SEQ_NO 4 ONLY CHILD 3
REQUESTS_IN .............. 1
ROWS_OUT ............. 5,000
EST_OPER_COST ............ 0
EST_TOTAL_COST ........... 0.01
DESCRIPTION
max_card_est ....... 5,000
fragment_id ............ 0
parent_frag ............ (none)
fragment_type .......... master
statement_index ........ 0
affinity_value ......... 0
est_memory_per_cpu ..... 260 KB
max_max_cardinality 5,000
total_overflow_size .... 0.00 KB
xn_access_mode ......... read_only
xn_autoabort_interval 0
auto_query_retry ....... enabled
plan_version ....... 2,600
embedded_arkcmp ........ used
LDAP_USERNAME .......... ZZ
SHOWCONTROL_SHOW_ALL ... OFF
GENERATE_EXPLAIN ....... ON
ObjectUIDs ............. 7186168948089148044, 7186168948089146661
select_list ............ TRAFODION.SEABASE.TEST1.A,
TRAFODION.SEABASE.TEST1.B,
TRAFODION.SEABASE.TEST2.B
input_variables ........ execution_count
HYBRID_HASH_JOIN ========================== SEQ_NO 3 CHILDREN 2, 1
REQUESTS_IN .............. 1
ROWS_OUT ............. 5,000
EST_OPER_COST ............ 0.01
EST_TOTAL_COST ........... 0.01
DESCRIPTION
memory_quota ........... 656 MB
max_card_est ....... 5,000
fragment_id ............ 0
parent_frag ............ (none)
fragment_type .......... master
est_memory_per_cpu ..... 260 KB
join_type .............. inner
join_method ............ hash
hash_join_predicates ... (TRAFODION.SEABASE.TEST1.A =
TRAFODION.SEABASE.TEST2.A)
TRAFODION_SCAN ============================ SEQ_NO 2 NO CHILDREN
TABLE_NAME ............... TEST1
REQUESTS_IN .............. 1
ROWS_OUT ............... 100
EST_OPER_COST ............ 0.01
EST_TOTAL_COST ........... 0.01
DESCRIPTION
max_card_est ......... 100
fragment_id ............ 0
parent_frag ............ (none)
fragment_type .......... master
scan_type .............. subset scan of table TRAFODION.SEABASE.TEST1
object_type ............ Trafodion
columns ................ all
begin_keys(incl)
end_keys(incl)
cache_size ........... 100
probes ................. 1
rows_accessed ........ 100
column_retrieved ....... #1:1,#1:2,#1:3
key_columns ............ SYSKEY
TRAFODION_SCAN ============================ SEQ_NO 1 NO CHILDREN
TABLE_NAME ............... TEST2
REQUESTS_IN .............. 1
ROWS_OUT ............... 100
EST_OPER_COST ............ 0.01
EST_TOTAL_COST ........... 0.01
DESCRIPTION
max_card_est ......... 100
fragment_id ............ 0
parent_frag ............ (none)
fragment_type .......... master
scan_type .............. subset scan of table TRAFODION.SEABASE.TEST2
object_type ............ Trafodion
columns ................ all
begin_keys(incl)
end_keys(incl)
cache_size ........... 100
probes ................. 1
rows_accessed ........ 100
column_retrieved ....... #1:1,#1:2,#1:3
key_columns ............ SYSKEY
--- SQL operation complete.3 explain options 'f' + sql 查看执行计划
SQL>explain options 'f'
+>select test1.a, test1.b, test2.b
+>from test1, test2
+>where test1.a = test2.a;
LC RC OP OPERATOR OPT DESCRIPTION CARD
---- ---- ---- -------------------- -------- -------------------- ---------
3 . 4 root 5.00E+003
2 1 3 hybrid_hash_join 5.00E+003
. . 2 trafodion_scan TEST1 1.00E+002
. . 1 trafodion_scan TEST2 1.00E+002
--- SQL operation complete.4 prepare + explain 查看执行计划
SQL>prepare s from
+>select test1.a, test1.b, test2.b
+>from test1, test2
+>where test1.a = test2.a;
--- SQL command prepared.
SQL>explain options 'f' s;
LC RC OP OPERATOR OPT DESCRIPTION CARD
---- ---- ---- -------------------- -------- -------------------- ---------
3 . 4 root 5.00E+003
2 1 3 hybrid_hash_join 5.00E+003
. . 2 trafodion_scan TEST1 1.00E+002
. . 1 trafodion_scan TEST2 1.00E+002
--- SQL operation complete.