Neoview Query Guide (R2.2)

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in-memory hash table. If the inner table is too large, it is subject to overflow to disk, which is

expensive and slow. The original row order is not guaranteed unless ordered hash joins are used.

HYBRID_HASH_JOIN Operator

The HYBRID_HASH_JOIN operator joins the data from two child tables. It creates a hash table

for the inner table and joins the outer table by hashing each outer row and looking for matches

in the hash table. This operator can overflow to disk when the inner table is too large to fit in

memory. Equijoins and cross-products are supported by this operator.

The HYBRID_HASH_JOIN 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 or natural joinjoin_type

textName of join method: hashjoin_method

text1 for Type1 or 2 for Type2, depending on parallel join algorithmparallel_join_type

expr(text)Expression of the join predicatehash_join_predicate

expr(text)Expression of the WHERE clause that is not included in a

hash_join_predicate or one of the child scans

selection_predicates

HYBRID_HASH_SEMI_JOIN Operator

The HYBRID_HASH_SEMI_JOIN returns only one row for every outer row, regardless of the

number of matches. The HYBRID_HASH_SEMI_JOIN operator differs from the

HYBRID_HASH_JOIN operator only when it finds multiple matches in the inner table. In the

HYBRID_HASH_JOIN case, a result row is returned for every match in the inner table. See

“HYBRID_HASH_JOIN Operator” (page 42).

The HYBRID_HASH_SEMI_JOIN operator has two child operators. The description field for

this operator contains: