Neoview Query Guide (R2.2)

It is important to be able to identify the process in which an operation occurs. Process boundaries
are identified by these operators:
• ROOT operator. This operator and all operators under it execute inside the master executor
(also called root process) until another process boundary is reached. Operators that can
execute within the master executor process include sort, groupby, and join operators.
• ESP_EXCHANGE operator. This operator operates partially in the master process and
partially in the executor server process (ESP). All operators under it execute inside an ESP
process or until another process boundary is reached. This operator represents the transfer
of data between two sets of processes: bottom processes that produce output rows and top
processes that receive the rows produced by the bottom processes. Operators that can execute
within the ESP process include sort, groupby, and join operators.
• PARTITION_ACCESS operator. This operator operates partially in the master/ESP process
and partially in the DAM process. All operators under it execute within a DAM process.
Operators that can execute within the DAM process include scan and groupby operators.
NOTE: Data Access Manager (DAM) is the disk process. DP2 is also used to represent the
disk process.
This example shows a plan in VQP with the process boundaries identified:
For more information about process architecture and parallelism, see Chapter 2 (page 19).
ROOT Operator
The ROOT operator is the root, or the top operator, of an execution plan and describes the SQL
query. This operator and all operators subordinate to it execute inside the master process until
another process boundary (ESP process or DAM process) is reached. The ROOT operator appears
in every query execution plan.
The ROOT operator has one 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.
The value used is returned if this optimization is used. Blank if not
used.
olt_optimization
integerStatement index of this statement.statement_index
Operators and Description Fields 33