Performance of corelated subquery

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Performance of corelated subquery

Currently we have teradata 14 system. I often see a high impact CPU for corelated subqueries. Ex. A query with 4k CPU has ImpactCPU of 10k. My question is how much a coreated subquery efficiently works in teradata. Thanx.

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2 REPLIES
Junior Supporter

Re: Performance of corelated subquery

H.

Impact CPU is related to skew. Your correlated subqueries are causing several AMPs work more than others.

Cheers.

Carlos.

Junior Contributor

Re: Performance of corelated subquery

What kind of Correlated Subqueries?

Scalar within the SELECT list?

Using non-equality conditions?