spark技术分享TypeCoercionRule Contract — Type Coercion Rules
TypeCoercionRule is the contract of logical rules to coerce and propagate types in logical plans.
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package org.apache.spark.sql.catalyst.analysis trait TypeCoercionRule extends Rule[LogicalPlan] { // only required methods that have no implementation // the others follow def coerceTypes(plan: LogicalPlan): LogicalPlan } |
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Coerce types in a logical plan Used exclusively when |
TypeCoercionRule is simply a Catalyst rule for transforming logical plans, i.e. Rule[LogicalPlan].
| TypeCoercionRule | Description |
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CaseWhenCoercion |
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ConcatCoercion |
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DecimalPrecision |
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Division |
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EltCoercion |
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FunctionArgumentConversion |
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IfCoercion |
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ImplicitTypeCasts |
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PromoteStrings |
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StackCoercion |
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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 coerceTypes in the input LogicalPlan and returns the following:
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The input LogicalPlan itself if matches the coerced plan
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The plan after propagateTypes on the coerced plan
propagateTypes Internal Method
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propagateTypes(plan: LogicalPlan): LogicalPlan |
propagateTypes…FIXME
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Note
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propagateTypes is used exclusively when TypeCoercionRule is executed.
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