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LogicalPlanVisitor — Contract for Computing Statistic Estimates and Query Hints of Logical Plan

LogicalPlanVisitor is the <> that uses the <> to scan a logical query plan and compute estimates of plan statistics and query hints.

TIP: Read about the visitor design pattern in https://en.wikipedia.org/wiki/Visitor_pattern[Wikipedia].

[[visit]] LogicalPlanVisitor defines visit method that dispatches computing the statistics of a logical plan to the <>.

[source, scala]

visit(p: LogicalPlan): T

NOTE: T stands for the type of a result to be computed (while visiting the query plan tree) and is currently always Statistics only.

The <> LogicalPlanVisitor is chosen per spark-sql-cost-based-optimization.md#spark.sql.cbo.enabled[spark.sql.cbo.enabled] configuration property. When turned on (i.e. true), LogicalPlanStats uses <> while <> otherwise.

[[implementations]] .LogicalPlanVisitors [cols="1,2",options="header",width="100%"] |=== | LogicalPlanVisitor | Description

[[BasicStatsPlanVisitor]] BasicStatsPlanVisitor
[[SizeInBytesOnlyStatsPlanVisitor]] SizeInBytesOnlyStatsPlanVisitor
===

[[contract]] [[handlers]] .LogicalPlanVisitor's Logical Operators and Their Handlers [cols="1,2",options="header",width="100%"] |=== | Logical Operator | Handler

| [[Aggregate]] Aggregate.md[Aggregate] | [[visitAggregate]] visitAggregate

| [[Distinct]] Distinct | visitDistinct

| [[Except]] Except | visitExcept

| [[Expand]] Expand.md[Expand] | visitExpand

| [[Filter]] Filter | [[visitFilter]] visitFilter

| [[Generate]] Generate.md[Generate] | visitGenerate

| [[GlobalLimit]] GlobalLimit | visitGlobalLimit

| [[Intersect]] Intersect | [[visitIntersect]] visitIntersect

| [[Join]] Join.md[Join] | [[visitJoin]] visitJoin

| [[LocalLimit]] LocalLimit | visitLocalLimit

| [[Pivot]] Pivot.md[Pivot] | visitPivot

| [[Project]] Project.md[Project] | [[visitProject]] visitProject

| [[Repartition]] Repartition | visitRepartition

| [[RepartitionByExpression]] RepartitionByExpression | visitRepartitionByExpr

| [[ResolvedHint]] ResolvedHint.md[ResolvedHint] | visitHint

| [[Sample]] Sample | visitSample

| [[ScriptTransformation]] ScriptTransformation | visitScriptTransform

| [[Union]] Union | visitUnion

| [[Window]] Window.md[Window] | visitWindow

| [[LogicalPlan]] Other spark-sql-LogicalPlan.md[logical operators] | default |===

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