spark技术分享EliminateSubqueryAliases Logical Optimization
EliminateSubqueryAliases is a base logical optimization that removes (eliminates) SubqueryAlias logical operators from a logical query plan.
EliminateSubqueryAliases is part of the Finish Analysis once-executed batch in the standard batches of the Catalyst Optimizer.
EliminateSubqueryAliases is simply a Catalyst rule for transforming logical plans, i.e. Rule[LogicalPlan].
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// Using Catalyst DSL import org.apache.spark.sql.catalyst.dsl.plans._ val t1 = table("t1") val logicalPlan = t1.subquery('a) import org.apache.spark.sql.catalyst.analysis.EliminateSubqueryAliases val afterEliminateSubqueryAliases = EliminateSubqueryAliases(logicalPlan) scala> println(afterEliminateSubqueryAliases.numberedTreeString) 00 'UnresolvedRelation `t1` |
Executing Rule — apply Method
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apply(plan: LogicalPlan): LogicalPlan |
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Note
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apply is part of the Rule Contract to execute (apply) a rule on a TreeNode (e.g. LogicalPlan).
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apply simply removes (eliminates) SubqueryAlias unary logical operators from the input logical plan.
