public class SharedWorkOptimizer extends Transform
Originally, this rule would find scan operators over the same table in the query plan and merge them if they met some preconditions. TS TS TS | | -> / \ Op Op Op Op
Now the rule has been extended to find opportunities to other operators downstream, not only a single table scan. TS1 TS2 TS1 TS2 TS1 TS2 | | | | | | | RS | RS | RS \ / \ / -> \ / MapJoin MapJoin MapJoin | | / \ Op Op Op Op
If the extended version of the optimizer is enabled, it can go beyond a work boundary to find reutilization opportunities.
The optimization only works with the Tez execution engine.
Constructor and Description |
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SharedWorkOptimizer() |
Modifier and Type | Method and Description |
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ParseContext |
transform(ParseContext pctx)
All transformation steps implement this interface.
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beginPerfLogging, endPerfLogging, endPerfLogging
public ParseContext transform(ParseContext pctx) throws SemanticException
Transform
transform
in class Transform
pctx
- input parse contextSemanticException
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