Neoview Query Guide (R2.2)

MERGE_ANTI_SEMI_JOIN Operator
The MERGE_ANTI_SEMI_JOIN operator returns rows only when no match occurs in the inner
table. The operator discards all rows that have a match. Also see “MERGE_JOIN Operator”
(page 40) and “MERGE_SEMI_JOIN Operator” (page 40).
The MERGE_ANTI_SEMI_JOIN operator has two child operators. The description field for this
operator contains:
Data TypeToken DescriptionToken
integerA sequential number assigned to the fragment. 0 is always master executor
and 1 is reserved for the Explain plan. Numbers 2 to n will be ESP or DAM
fragments.
fragment_id
integerThe fragment_id for the parent fragment of the current fragment. Value
is (none) for master executor.
parent_frag
textmaster, ESP, or DAMfragment_type
textInner anti-semi or natural anti-semi-joinjoin_type
textName of join method: mergejoin_method
text1 for Type1 or 2 for Type2, depending on parallel join algorithmparallel_join_type
expr(text)Expression of the join predicatemerge_join_predicate
expr(text)Expression of the WHERE clause that is not included in the
merge_join_predicate or in a selection_predicates of any children
selection_predicates
LEFT_MERGE_JOIN Operator
The LEFT_MERGE_JOIN operator describes a portion of an execution plan that involves a merge
join. The LEFT_MERGE_JOIN differs from MERGE_JOIN only when it does not find a match in
the inner table. When no match is found, the left row is still returned, and the data from the right
table is set to null. See “MERGE_JOIN Operator” (page 40).
The LEFT_MERGE_JOIN operator has two child operators. The description field for this operator
contains:
Data TypeToken DescriptionToken
integerA sequential number assigned to the fragment. 0 is always master
executor and 1 is reserved for the Explain plan. Numbers 2 to n will be
ESP or DAM fragments.
fragment_id
integerThe fragment_id for the parent fragment of the current fragment. Value
is (none) for master executor.
parent_frag
textmaster, ESP, or DAMfragment_type
textLeft joinjoin_type
textName of join method: mergejoin_method
text1 for Type1 or 2 for Type2, depending on parallel join algorithmparallel_join_type
expr(text)Expression of the join predicatemerge_join_predicate
expr(text)Expression of the WHERE clause that is not included in the
merge_join_predicate or in a selection_predicates of any children
selection_predicates
Hybrid Hash Joins
In a hybrid hash join, the inner table is hashed on the join column into the memory of the process
doing the join. The outer table is read and the join column is hashed and matched against the
Understanding Joins 41