SQL/MX 3.2.1 Query Guide (H06.26+, J06.15+)

SQL/MX Operators
HP NonStop SQL/MX Release 3.2.1 Query Guide—663851-003
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ESP_EXCHANGE Operator
ESP_EXCHANGE Operator
Exchange Group
An ESP_EXCHANGE operator describes a portion of an execution plan that
redistributes the input data stream. This operator represents an interface between
ESPs, between the master executor and one or more ESPs, or between an ESP
process and a DAM process. For more information about exchange operators, see
Section 8, Parallelism.
The ESP_EXCHANGE operator has one child node. The description field for this
operator contains the following:
Token Followed by ... Data Type
fragment_id A sequential number assigned to the
fragment. 0 is always the master
executor and 1 is reserved for the
EXPLAIN plan. Numbers 2 to n will be
ESP or DAM fragments.
integer
parent_frag The fragment_id for the parent of the
current fragment. The value is (none)
for the master executor.
integer
fragment_type Master, ESP, or DP2. text
buffer_size Size of message buffer. integer
record_length Number of bytes in the record sent. integer
parent_processes Indicates the number of processes that
the ESPs in the ESP_EXCHANGE
operator communicates with either
additional ESPs (as indicated by
another ESP_EXCHANGE operator) or
the master process.
integer
child_processes Indicates the number of processes that
supply the ESPs of an operator with
rows. The number of ROWS_OUT
(also called CARDINALITY) from the
operator that supplies the
ESP_EXCHANGE operator with data
indicates how many rows the
ESP_EXCHANGE operator is
expected to receive.
integer
parent_partitioning_function Type of top partitioning and contains
summary information about the parallel
plan.
text
child_partitioning_function Indicates how the input data received
by the ESP_EXCHANGE operator is
organized.
text
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