Amazon Redshift
Database Developer Guide

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Mapping the Query Plan to the Query Summary

It helps to map the operations from the query plan to the steps (identified by the label field values) in the query summary to get further details on them:

Query Plan Operation Label Field Value Description




AGGR Evaluates aggregate functions and GROUP BY conditions.
DS_BCAST_INNER BCAST (broadcast) Broadcasts an entire table or some set of rows (such as a filtered set of rows from a table) to all nodes.
Doesn’t appear in query plan DELETE Deletes rows from tables.






DIST (distribute) Distributes rows to nodes for parallel joining purposes or other parallel processing.
HASH HASH Builds hash table for use in hash joins.
Hash Join HJOIN (hash join) Executes a hash join of two tables or intermediate result sets.
Doesn’t appear in query plan INSERT Inserts rows into tables.
Limit LIMIT Applies a LIMIT clause to result sets.
Merge MERGE Merges rows derived from parallel sort or join operations.
Merge Join MJOIN (merge join) Executes a merge join of two tables or intermediate result sets.
Nested Loop NLOOP (nested loop) Executes a nested loop join of two tables or intermediate result sets.
Doesn’t appear in query plan PARSE Parses strings into binary values for loading.
Project PROJECT Evaluates expressions.
Network RETURN Returns rows to the leader or the client.
Doesn’t appear in query plan SAVE Materializes rows for use in the next processing step.
Seq Scan SCAN Scans tables or intermediate result sets.
Sort SORT Sorts rows or intermediate result sets as required by other subsequent operations (such as joins or aggregations) or to satisfy an ORDER BY clause.
Unique UNIQUE Applies a SELECT DISTINCT clause or removes duplicates as required by other operations.
Window WINDOW Computes aggregate and ranking window functions.