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https://issues.apache.org/jira/browse/HIVE-17696?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16226071#comment-16226071
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Vihang Karajgaonkar commented on HIVE-17696:
--------------------------------------------
Thanks [~Ferd] Can you also please merge this patch to branch-2?
> Vectorized reader does not seem to be pushing down projection columns in
> certain code paths
> -------------------------------------------------------------------------------------------
>
> Key: HIVE-17696
> URL: https://issues.apache.org/jira/browse/HIVE-17696
> Project: Hive
> Issue Type: Sub-task
> Reporter: Vihang Karajgaonkar
> Assignee: Ferdinand Xu
> Fix For: 3.0.0
>
> Attachments: HIVE-17696.2.patch, HIVE-17696.patch
>
>
> This is the code snippet from {{VectorizedParquetRecordReader.java}}
> {noformat}
> MessageType tableSchema;
> if (indexAccess) {
> List<Integer> indexSequence = new ArrayList<>();
> // Generates a sequence list of indexes
> for(int i = 0; i < columnNamesList.size(); i++) {
> indexSequence.add(i);
> }
> tableSchema = DataWritableReadSupport.getSchemaByIndex(fileSchema,
> columnNamesList,
> indexSequence);
> } else {
> tableSchema = DataWritableReadSupport.getSchemaByName(fileSchema,
> columnNamesList,
> columnTypesList);
> }
> indexColumnsWanted =
> ColumnProjectionUtils.getReadColumnIDs(configuration);
> if (!ColumnProjectionUtils.isReadAllColumns(configuration) &&
> !indexColumnsWanted.isEmpty()) {
> requestedSchema =
> DataWritableReadSupport.getSchemaByIndex(tableSchema,
> columnNamesList, indexColumnsWanted);
> } else {
> requestedSchema = fileSchema;
> }
> this.reader = new ParquetFileReader(
> configuration, footer.getFileMetaData(), file, blocks,
> requestedSchema.getColumns());
> {noformat}
> Couple of things to notice here:
> Most of this code is duplicated from {{DataWritableReadSupport.init()}}
> method.
> the else condition passes in fileSchema instead of using tableSchema like we
> do in DataWritableReadSupport.init() method. Does this cause projection
> columns to be missed when we read parquet files? We should probably just
> reuse ReadContext returned from {{DataWritableReadSupport.init()}} method
> here.
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