Optimizer与一样，也是继承自RuleExecutor,匹配规则对SQL进行优化
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lazy val withCachedData: LogicalPlan = {
assertAnalyzed()
assertSupported()
sparkSession.sharedState.cacheManager.useCachedData(analyzed)
}
lazy val optimizedPlan: LogicalPlan = sparkSession.sessionState.optimizer.execute(withCachedData)
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def execute(plan: TreeType): TreeType = {
var curPlan = plan
val queryExecutionMetrics = RuleExecutor.queryExecutionMeter
batches.foreach { batch =>
val batchStartPlan = curPlan
var iteration = 1
var lastPlan = curPlan
var continue = true
// Run until fix point (or the max number of iterations as specified in the strategy.
while (continue) {
curPlan = batch.rules.foldLeft(curPlan) {
case (plan, rule) =>
val startTime = System.nanoTime()
val result = rule(plan)
val runTime = System.nanoTime() - startTime
if (!result.fastEquals(plan)) {
queryExecutionMetrics.incNumEffectiveExecution(rule.ruleName)
queryExecutionMetrics.incTimeEffectiveExecutionBy(rule.ruleName, runTime)
logTrace(
s"""
|=== Applying Rule ${rule.ruleName} ===
|${sideBySide(plan.treeString, result.treeString).mkString("\n")}
""".stripMargin)
}
queryExecutionMetrics.incExecutionTimeBy(rule.ruleName, runTime)
queryExecutionMetrics.incNumExecution(rule.ruleName)
// Run the structural integrity checker against the plan after each rule.
if (!isPlanIntegral(result)) {
val message = s"After applying rule ${rule.ruleName} in batch ${batch.name}, " +
"the structural integrity of the plan is broken."
throw new TreeNodeException(result, message, null)
}
result
}
iteration += 1
if (iteration > batch.strategy.maxIterations) {
// Only log if this is a rule that is supposed to run more than once.
if (iteration != 2) {
val message = s"Max iterations (${iteration - 1}) reached for batch ${batch.name}"
if (Utils.isTesting) {
throw new TreeNodeException(curPlan, message, null)
} else {
logWarning(message)
}
}
continue = false
}
if (curPlan.fastEquals(lastPlan)) {
logTrace(
s"Fixed point reached for batch ${batch.name} after ${iteration - 1} iterations.")
continue = false
}
lastPlan = curPlan
}
if (!batchStartPlan.fastEquals(curPlan)) {
logDebug(
s"""
|=== Result of Batch ${batch.name} ===
|${sideBySide(batchStartPlan.treeString, curPlan.treeString).mkString("\n")}
""".stripMargin)
} else {
logTrace(s"Batch ${batch.name} has no effect.")
}
}
curPlan
}