Node name: TQ
Represents: A table queue that is used to pass table data from one database agent to another when there are multiple database agents processing a query. Multiple database agents are used to process a query when parallelism is involved.
Based on the origin type, TQ nodes are of two types:
The XTQ node is a table queue that constructs a XML sequence from XML documents stored on database partitions.
Xquery let $all_orders := db2-fn:xmlcolumn('US_ORDERS.DETAILS')where
sum($all_orders//product/qty) > 100return
$all_ordersFor the XQuery statement, the db2exfmt command produces the following access plan output that contains an XTQ node. In the plan output, references to all the XML documents stored in US_ORDERS.DETAILS column are routed (DTQ: Directed TQ) to the coordinator partition and aggregated into a global sequence, later each item in the global sequence is routed back to its original partition for navigation and the results are aggregated together into a new output global sequence (XTQ: XSCAN related TQ).
Rows RETURN ( 1) Cost I/O | 1 NLJOIN ( 2) 98.171 8 /-+-\ 1 2000 FILTER XTQ ( 3) ( 7) 37.4289 60.7421 1 7 | | 1 0.5 GRPBY XSCAN ( 4) ( 8) 37.3755 57.2 1 7 | 360 DTQ ( 5) 33.7655 1 | 180 TBSCAN ( 6) 22.051 1 | 180 TABLE: USER1 US_ORDERS