Github user gatorsmile commented on a diff in the pull request:

    https://github.com/apache/spark/pull/14155#discussion_r75565740
  
    --- Diff: 
sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveExternalCatalog.scala ---
    @@ -144,16 +164,162 @@ private[spark] class HiveExternalCatalog(client: 
HiveClient, hadoopConf: Configu
         assert(tableDefinition.identifier.database.isDefined)
         val db = tableDefinition.identifier.database.get
         requireDbExists(db)
    +    verifyTableProperties(tableDefinition)
    +
    +    // Before saving data source table metadata into Hive metastore, we 
should:
    +    //  1. Put table schema, partition column names and bucket 
specification in table properties.
    +    //  2. Check if this table is hive compatible
    +    //    2.1  If it's not hive compatible, set schema, partition columns 
and bucket spec to empty
    +    //         and save table metadata to Hive.
    +    //    2.1  If it's hive compatible, set serde information in table 
metadata and try to save
    +    //         it to Hive. If it fails, treat it as not hive compatible 
and go back to 2.1
    +    if (DDLUtils.isDatasourceTable(tableDefinition)) {
    +      // data source table always have a provider, it's guaranteed by 
`DDLUtils.isDatasourceTable`.
    +      val provider = tableDefinition.provider.get
    +      val partitionColumns = tableDefinition.partitionColumnNames
    +      val bucketSpec = tableDefinition.bucketSpec
    +
    +      val tableProperties = new scala.collection.mutable.HashMap[String, 
String]
    +      tableProperties.put(DATASOURCE_PROVIDER, provider)
    +
    +      // Serialized JSON schema string may be too long to be stored into a 
single metastore table
    +      // property. In this case, we split the JSON string and store each 
part as a separate table
    +      // property.
    +      // TODO: the threshold should be set by 
`spark.sql.sources.schemaStringLengthThreshold`,
    +      // however the current SQLConf is session isolated, which is not 
applicable to external
    +      // catalog. We should re-enable this conf instead of hard code the 
value here, after we have
    +      // global SQLConf.
    +      val threshold = 4000
    +      val schemaJsonString = tableDefinition.schema.json
    +      // Split the JSON string.
    +      val parts = schemaJsonString.grouped(threshold).toSeq
    +      tableProperties.put(DATASOURCE_SCHEMA_NUMPARTS, parts.size.toString)
    +      parts.zipWithIndex.foreach { case (part, index) =>
    +        tableProperties.put(s"$DATASOURCE_SCHEMA_PART_PREFIX$index", part)
    +      }
    +
    +      if (partitionColumns.nonEmpty) {
    +        tableProperties.put(DATASOURCE_SCHEMA_NUMPARTCOLS, 
partitionColumns.length.toString)
    +        partitionColumns.zipWithIndex.foreach { case (partCol, index) =>
    +          tableProperties.put(s"$DATASOURCE_SCHEMA_PARTCOL_PREFIX$index", 
partCol)
    +        }
    +      }
    +
    +      if (bucketSpec.isDefined) {
    +        val BucketSpec(numBuckets, bucketColumnNames, sortColumnNames) = 
bucketSpec.get
    +
    +        tableProperties.put(DATASOURCE_SCHEMA_NUMBUCKETS, 
numBuckets.toString)
    +        tableProperties.put(DATASOURCE_SCHEMA_NUMBUCKETCOLS, 
bucketColumnNames.length.toString)
    +        bucketColumnNames.zipWithIndex.foreach { case (bucketCol, index) =>
    +          
tableProperties.put(s"$DATASOURCE_SCHEMA_BUCKETCOL_PREFIX$index", bucketCol)
    +        }
    +
    +        if (sortColumnNames.nonEmpty) {
    +          tableProperties.put(DATASOURCE_SCHEMA_NUMSORTCOLS, 
sortColumnNames.length.toString)
    +          sortColumnNames.zipWithIndex.foreach { case (sortCol, index) =>
    +            
tableProperties.put(s"$DATASOURCE_SCHEMA_SORTCOL_PREFIX$index", sortCol)
    +          }
    +        }
    +      }
    +
    +      // converts the table metadata to Spark SQL specific format, i.e. 
set schema, partition column
    +      // names and bucket specification to empty.
    +      def newSparkSQLSpecificMetastoreTable(): CatalogTable = {
    +        tableDefinition.copy(
    +          schema = new StructType,
    +          partitionColumnNames = Nil,
    +          bucketSpec = None,
    +          properties = tableDefinition.properties ++ tableProperties)
    +      }
    +
    +      // converts the table metadata to Hive compatible format, i.e. set 
the serde information.
    +      def newHiveCompatibleMetastoreTable(serde: HiveSerDe, path: String): 
CatalogTable = {
    +        tableDefinition.copy(
    +          storage = tableDefinition.storage.copy(
    +            locationUri = Some(new Path(path).toUri.toString),
    +            inputFormat = serde.inputFormat,
    +            outputFormat = serde.outputFormat,
    +            serde = serde.serde
    +          ),
    +          properties = tableDefinition.properties ++ tableProperties)
    +      }
    +
    +      val qualifiedTableName = tableDefinition.identifier.quotedString
    +      val maybeSerde = 
HiveSerDe.sourceToSerDe(tableDefinition.provider.get)
    +      val maybePath = new 
CaseInsensitiveMap(tableDefinition.storage.properties).get("path")
    +      val skipHiveMetadata = tableDefinition.storage.properties
    +        .getOrElse("skipHiveMetadata", "false").toBoolean
    +
    +      val (hiveCompatibleTable, logMessage) = (maybeSerde, maybePath) 
match {
    +        case _ if skipHiveMetadata =>
    +          val message =
    +            s"Persisting data source table $qualifiedTableName into Hive 
metastore in" +
    +              "Spark SQL specific format, which is NOT compatible with 
Hive."
    +          (None, message)
    +
    +        // our bucketing is un-compatible with hive(different hash 
function)
    +        case _ if tableDefinition.bucketSpec.nonEmpty =>
    +          val message =
    +            s"Persisting bucketed data source table $qualifiedTableName 
into " +
    +              "Hive metastore in Spark SQL specific format, which is NOT 
compatible with Hive. "
    +          (None, message)
    +
    +        case (Some(serde), Some(path)) =>
    +          val message =
    +            s"Persisting data source table $qualifiedTableName with a 
single input path " +
    --- End diff --
    
    It sounds like it is impossible to provide multiple input paths in the 
write path of data source tables. Maybe we can update the message here?


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