public class IdentityProjectRemover extends Transform
SelectOperatorfrom tree which don't do any processing except forwarding columns from its parent to its children. e.g., select * from (select * from src where key = value) t1 join (select * from src where key = value) t2; Query tree Without this optimization: TS -> FIL -> SEL -> RS -> JOIN -> SEL -> FS TS -> FIL -> SEL -> RS -> With this optimization TS -> FIL -> RS -> JOIN -> FS TS -> FIL -> RS -> Note absence of select operator after filter and after join operator. Also, see : identity_proj_remove.q
|Constructor and Description|
|Modifier and Type||Method and Description|
All transformation steps implement this interface.
beginPerfLogging, endPerfLogging, endPerfLogging
public ParseContext transform(ParseContext pctx) throws SemanticException
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