Postgres-XC tutorial PDF - PGCon

Replicated tables – mult­irow operation
Pushing aggregates to the datanodes for better performance
EXPLAIN VERBOSE SELECT sum(val) FROM tab1 GROUP BY val2;
QUERY PLAN
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Data Node Scan on "__REMOTE_FQS_QUERY__"
Output: sum(tab1.val), tab1.val2
Node/s: datanode_1
Remote query: SELECT sum(val) AS sum FROM tab1 GROUP BY val2
­­ Get grouped and aggregated results from datanodes
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Similarly push DISTINCT, ORDER BY etc.
May 16th, 2012 Postgres­XC 49