我正在使用基于成本的优化器（CBO）的 Spark 2.3.0 来计算在外部表上完成的查询的统计信息。
我在 spark 中创建了一个外部表：
CREATE EXTERNAL TABLE IF NOT EXISTS test (
eventID string,type string,exchange string,eventTimestamp bigint,sequenceNumber bigint
,optionID string,orderID string,side string,routingFirm string,routedOrderID string
,session string,price decimal(18,8),quantity bigint,timeInForce string,handlingInstructions string
,orderAttributes string,isGloballyUnique boolean,originalOrderID string,initiator string,leavesQty bigint
,symbol string,routedOriginalOrderID string,displayQty bigint,orderType string,coverage string
,result string,resultTimestamp bigint,nbbPrice decimal(18,8),nbbQty bigint,nboPrice decimal(18,8)
,nboQty bigint,reporter string,quoteID string,noteType string,definedNoteData string,undefinedNoteData string
,note string,desiredLeavesQty bigint,displayPrice decimal(18,8),workingPrice decimal(18,8),complexOrderID string
,complexOptionID string,cancelQty bigint,cancelReason string,openCloseIndicator string,exchOriginCode string
,executingFirm string,executingBroker string,cmtaFirm string,mktMkrSubAccount string,originalOrderDate string
,tradeID string,saleCondition string,executionCodes string,buyDetails_side string,buyDetails_leavesQty bigint
,buyDetails_openCloseIndicator string,buyDetails_quoteID string,buyDetails_orderID string,buyDetails_executingFirm string,buyDetails_executingBroker string,buyDetails_cmtaFirm string,buyDetails_mktMkrSubAccount string,buyDetails_exchOriginCode string,buyDetails_liquidityCode string,buyDetails_executionCodes string,sellDetails_side string,sellDetails_leavesQty bigint,sellDetails_openCloseIndicator string,sellDetails_quoteID string,sellDetails_orderID string,sellDetails_executingFirm string,sellDetails_executingBroker string,sellDetails_cmtaFirm string,sellDetails_mktMkrSubAccount string,sellDetails_exchOriginCode string,sellDetails_liquidityCode string,sellDetails_executionCodes string,tradeDate int,reason string,executionTimestamp bigint,capacity string,fillID string,clearingNumber string
,contraClearingNumber string,buyDetails_capacity string,buyDetails_clearingNumber string,sellDetails_capacity string
,sellDetails_clearingNumber string,receivingFirm string,marketMaker string,sentTimestamp bigint,onlyOneQuote boolean
,originalQuoteID string,bidPrice decimal(18,8),bidQty bigint,askPrice decimal(18,8),askQty bigint,declaredTimestamp bigint,revokedTimestamp bigint,awayExchange string,comments string,clearingFirm string )
PARTITIONED BY (date integer ,reporteIDs string ,version integer )
STORED AS PARQUET LOCATION '/home/test/'
我使用以下命令计算了列的统计信息：
val df = spark.read.parquet("/home/test/")
val cols = df.columns.mkString(",")
val analyzeDDL = s"Analyze table events compute statistics for columns $cols"
spark.sql(analyzeDDL)
现在，当我尝试获取查询的统计信息时：
val query = "Select * from test where date > 20180222"
它只给我 size 而不是 rowCount ：
scala> val exec = spark.sql(query).queryExecution
exec: org.apache.spark.sql.execution.QueryExecution =
== Parsed Logical Plan ==
'Project [*]
+- 'Filter ('date > 20180222)
+- 'UnresolvedRelation `test`
== Analyzed Logical Plan ==
eventID: string, type: string, exchange: string, eventTimestamp: bigint, sequenceNumber: bigint, optionID: string, orderID: string, side: string, routingFirm: string, routedOrderID: string, session: string, price: decimal(18,8), quantity: bigint, timeInForce: string, handlingInstructions: string, orderAttributes: string, isGloballyUnique: boolean, originalOrderID: string, initiator: string, leavesQty: bigint, symbol: string, routedOriginalOrderID: string, displayQty: bigint, orderType: string, ... 82 more fields
Project [eventID#797974, type#797975, exchange#797976, eventTimestamp#797977L, sequenceNumber#...
scala>
scala> val stats = exec.optimizedPlan.stats
stats: org.apache.spark.sql.catalyst.plans.logical.Statistics = Statistics(sizeInBytes=1.0 B, hints=none)
我在这里错过任何步骤吗？如何获取查询的行数。
Spark-version : 2.3.0 表中的文件为 parquet 格式。
更新 我能够获取 csv 文件的统计信息。无法为镶木地板文件获得相同的结果。
parquet 和 csv 的执行计划之间的区别在于格式，在 csv 中HiveTableRelation，parquet 的Relation.
知道为什么会这样吗？