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From gvramana <...@git.apache.org>
Subject [GitHub] incubator-carbondata pull request #641: [CARBONDATA-767] Alter table support...
Date Wed, 15 Mar 2017 06:50:51 GMT
Github user gvramana commented on a diff in the pull request:

    https://github.com/apache/incubator-carbondata/pull/641#discussion_r106090051
  
    --- Diff: integration/spark-common/src/main/scala/org/apache/carbondata/spark/util/CarbonScalaUtil.scala
---
    @@ -194,4 +196,102 @@ object CarbonScalaUtil {
           }
         }
       }
    +
    +  /**
    +   * This method will validate a column for its data type and check whether the column
data type
    +   * can be modified and update if conditions are met
    +   *
    +   * @param dataTypeInfo
    +   * @param carbonColumn
    +   */
    +  def validateColumnDataType(dataTypeInfo: DataTypeInfo, carbonColumn: CarbonColumn):
Unit = {
    +    carbonColumn.getDataType.getName match {
    +      case "INT" =>
    +        if (!dataTypeInfo.dataType.equals("bigint")) {
    +          sys
    +            .error(s"Given column ${ carbonColumn.getColName } with data type ${
    +              carbonColumn
    +                .getDataType.getName
    +            } cannot be modified. Int can only be changed to bigInt")
    +        }
    +      case "DECIMAL" =>
    +        if (!dataTypeInfo.dataType.equals("decimal")) {
    +          sys
    +            .error(s"Given column ${ carbonColumn.getColName } with data type ${
    +              carbonColumn.getDataType.getName
    +            } cannot be modified. Decimal can be only be changed to Decimal of higher
precision")
    +        }
    +        if (dataTypeInfo.precision <= carbonColumn.getColumnSchema.getPrecision) {
    +          sys
    +            .error(s"Given column ${
    +              carbonColumn
    +                .getColName
    +            } cannot be modified. Specified precision value ${
    +              dataTypeInfo
    +                .precision
    +            } should be greater or equal to current precision value ${
    +              carbonColumn.getColumnSchema
    +                .getPrecision
    +            }")
    +        } else if (dataTypeInfo.scale <= carbonColumn.getColumnSchema.getScale) {
    +          sys
    +            .error(s"Given column ${
    +              carbonColumn
    +                .getColName
    +            } cannot be modified. Specified scale value ${
    +              dataTypeInfo
    +                .scale
    +            } should be greater or equal to current scale value ${
    +              carbonColumn.getColumnSchema
    +                .getScale
    +            }")
    +        } else {
    +          // difference of precision and scale specified by user should not be less than
the
    +          // difference of already existing precision and scale else it will result in
data loss
    +          val carbonColumnPrecisionScaleDiff = carbonColumn.getColumnSchema.getPrecision
-
    +                                               carbonColumn.getColumnSchema.getScale
    +          val dataInfoPrecisionScaleDiff = dataTypeInfo.precision - dataTypeInfo.scale
    +          if (dataInfoPrecisionScaleDiff < carbonColumnPrecisionScaleDiff) {
    +            sys
    +              .error(s"Given column ${
    +                carbonColumn
    +                  .getColName
    +              } cannot be modified. Specified precision and scale values will lead to
data loss")
    +          }
    +        }
    +      case _ =>
    +        sys
    +          .error(s"Given column ${ carbonColumn.getColName } with data type ${
    +            carbonColumn
    +              .getDataType.getName
    +          } cannot be modified. Only Int and Decimal data types are allowed for modification")
    +    }
    +  }
    +
    +  /**
    +   * This method will create a copy of the same object
    +   *
    +   * @param thriftColumnSchema object to be cloned
    +   * @return
    +   */
    +  def createColumnSchemaCopyObject(thriftColumnSchema: org.apache.carbondata.format.ColumnSchema)
    --- End diff --
    
    Use schema copy will work, instead of writing new copy method


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