Neoview Query Guide (R2.3, R2.4, R2.5)

Data TypeToken DescriptionToken
textType of top partitioning and contains summary information
about the parallel plan. Usually includes one of three
functions: hash-partition, round-robin partition, or broadcast.
See “Repartitioning Rows .”
parent_partitioning_function
textIndicates how the input data received by the
ESP_EXCHANGE operator is organized. The operator that
supplies the ESP_EXCHANGE operator with data is normally
either a PARTITION_ACCESS operator or another
ESP_EXCHANGE operator. In either case, the child_processes
field reflects the partitioning method (if any) used to organize
the input data from that operator.
child_partitioning_function
textAssociates each process at the bottom to a CPUbottom_node_map
expr(text)Expression describing sort keys used to control the interaction
between the parent process (usually the master) and ESPs
when the result set is ordered. For example, an
ESP_EXCHANGE operator with multiple ESP processes may
be used to sort rows from a partitioned table on a nonkey
column. Each of the ESPs will contain a subset of rows sorted
on (potentially) the same values. To return the entire result
set in the proper sort sequence, the master will interact with
each of the ESPs to retrieve the sorted subsets in proper sort
order, effectively merging each subset from the ESPs into a
single sorted result set.
merged_order
textPrevents self-referencing anomalies during INSERT, UPDATE
or DELETE operations.
self_reference_update_protection
Repartitioning Rows
If the ESPs are used to repartition or redistribute the input rows to another set of ESP processes,
the repartition operation will appear in the parent_partitioning_function field of the current
ESP_EXCHANGE operator. The parent_partitioning_function field usually includes one of these
functions and indicates that the ESPs in this ESP_EXCHANGE operator:
• hash partition: Hashes each input row on the indicated columns and sends the results to the
corresponding parent processes. Each hash result value is a number that corresponds to one
of the parent processes. The result of hashing the input data groups the rows by the hash
columns and sends each group to the corresponding parent processes for further processing.
• round-robin partitioning: Assigns each input row to the corresponding parent processes in
a round-robin fashion. The result of round-robin partitioning the input data groups the rows
randomly and sends each group to the corresponding parent processes for further processing.
• broadcast: Broadcasts every input row to all parent processes. The result of broadcasting
the input data replicates the input rows and sends each replicate to the corresponding parent
processes for further processing.
PARTITION_ACCESS Operator
The PARTITION_ACCESS operator describes a portion of an execution plan for a file system
interface in which requests are made to DAM. This operator represents the DAM process
boundary. This operator and all operators subordinate to it execute inside a DAM. The DAM
process runs in parallel to the PARTITION_ACCESS (no-waited interface).
22 Query Plan Operators