Neoview Query Guide (R2.2)

Data TypeToken DescriptionToken
expr(text)Expression used to calculate the start partition number (appears
instead of begin_key_preds and begin_key_exclusion_expr)
begin_part_no_expr
expr(text)Expression used to calculate the end partition number (appears
instead of end_key_preds and end_key_exclusion_expr)
end_part_no_expr
textExpression used by SPLIT_TOP or PARTITION_ACCESS to
compute the begin_part_no_expr.
begin_part_selection_expr
textExpression used by SPLIT_TOP or PARTITION_ACCESS to
compute the end_part_no_expr.
end_part_selection_expr
textExpression used to generate the seed value. Appears only when
inserting into a table with an IDENTITY column.
sequence_init_expr
textExpression used to generate values for the IDENTITY column.
Values will be in sequence for this INSERT statement. Appears
only when inserting into a table with an IDENTITY column.
sequence_generation_expr
SPLIT_TOP Operator
The SPLIT_TOP operator describes a portion of an execution plan for a file system interface in
which requests to DAM occur with some level of parallel processing. No startup costs are
associated with the SPLIT_TOP operator. The SPLIT_TOP operator executes in either the master
executor or ESP process. It cannot execute in the DAM process. For more information about
exchange operators, see Chapter 2 (page 19).
The SPLIT_TOP operator always has a PARTITION_ACCESS operator as its child. 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
textIndicates whether an optimization for short, simple operations
is used. Value is used if this optimization is used.
olt_optimization
integerNumber of ESPs containing this operatorparent_processes
textType of top partitioning and contains summary information
about the parallel plan
parent_partitioning_function
integerNumber of bottom partitionschild_processes
textType of bottom partitioning and contains summary information
about the parallel plan
child_partitioning_function
textAssociates each process at the bottom to a CPUbottom_node_map
Understanding Joins
The Neoview database has three main join types: nested join, merge join, and hybrid hash join.
Within the join types, many join operators exist. The join types and operators that occur within
each type are described in this subsection.
All joins are binary, work with two tables and result sets at a time, and are distinguished by a
left side (also called the outer table/result set) and right side (also called the inner table/result
36 Query Plan Operators