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https://issues.apache.org/jira/browse/DRILL-7062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16812048#comment-16812048
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ASF GitHub Bot commented on DRILL-7062:
---------------------------------------
amansinha100 commented on pull request #1738: DRILL-7062: Initial
implementation of run-time row-group pruning
URL: https://github.com/apache/drill/pull/1738#discussion_r272869882
##########
File path:
exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/AbstractParquetScanBatchCreator.java
##########
@@ -68,76 +83,131 @@ protected ScanBatch getBatch(ExecutorFragmentContext
context, AbstractParquetRow
List<RecordReader> readers = new LinkedList<>();
List<Map<String, String>> implicitColumns = new ArrayList<>();
Map<String, String> mapWithMaxColumns = new LinkedHashMap<>();
- for (RowGroupReadEntry rowGroup : rowGroupScan.getRowGroupReadEntries()) {
- /*
- Here we could store a map from file names to footers, to prevent
re-reading the footer for each row group in a file
- TODO - to prevent reading the footer again in the parquet record reader
(it is read earlier in the ParquetStorageEngine)
- we should add more information to the RowGroupInfo that will be
populated upon the first read to
- provide the reader with all of th file meta-data it needs
- These fields will be added to the constructor below
- */
- try {
- Stopwatch timer = logger.isTraceEnabled() ?
Stopwatch.createUnstarted() : null;
- DrillFileSystem fs = fsManager.get(rowGroupScan.getFsConf(rowGroup),
rowGroup.getPath());
- ParquetReaderConfig readerConfig = rowGroupScan.getReaderConfig();
- if (!footers.containsKey(rowGroup.getPath())) {
- if (timer != null) {
- timer.start();
+ ParquetReaderConfig readerConfig = rowGroupScan.getReaderConfig();
+ RowGroupReadEntry firstRowGroup = null; // to be scanned in case ALL row
groups are pruned out
+ ParquetMetadata firstFooter = null;
+ long rowgroupsPruned = 0; // for stats
+
+ try {
+
+ LogicalExpression filterExpr = rowGroupScan.getFilter();
+ Path selectionRoot = rowGroupScan.getSelectionRoot();
+ // Runtime pruning: Avoid recomputing metadata objects for each
row-group in case they use the same file
+ // by keeping the following objects computed earlier (relies on same
file being in consecutive rowgroups)
+ Path prevRowGroupPath = null;
+ Metadata_V3.ParquetTableMetadata_v3 tableMetadataV3 = null;
+ Metadata_V3.ParquetFileMetadata_v3 fileMetadataV3 = null;
+ FileSelection fileSelection = null;
+ ParquetTableMetadataProviderImpl metadataProvider = null;
+
+ for (RowGroupReadEntry rowGroup : rowGroupScan.getRowGroupReadEntries())
{
+ /*
+ Here we could store a map from file names to footers, to prevent
re-reading the footer for each row group in a file
+ TODO - to prevent reading the footer again in the parquet record
reader (it is read earlier in the ParquetStorageEngine)
+ we should add more information to the RowGroupInfo that will be
populated upon the first read to
+ provide the reader with all of th file meta-data it needs
+ These fields will be added to the constructor below
+ */
+
+ Stopwatch timer = logger.isTraceEnabled() ?
Stopwatch.createUnstarted() : null;
+ DrillFileSystem fs = fsManager.get(rowGroupScan.getFsConf(rowGroup),
rowGroup.getPath());
+ if (!footers.containsKey(rowGroup.getPath())) {
+ if (timer != null) {
+ timer.start();
+ }
+
+ ParquetMetadata footer = readFooter(fs.getConf(),
rowGroup.getPath(), readerConfig);
+ if (timer != null) {
+ long timeToRead = timer.elapsed(TimeUnit.MICROSECONDS);
+ logger.trace("ParquetTrace,Read Footer,{},{},{},{},{},{},{}",
"", rowGroup.getPath(), "", 0, 0, 0, timeToRead);
+ }
+ footers.put(rowGroup.getPath(), footer);
}
+ ParquetMetadata footer = footers.get(rowGroup.getPath());
+
+ //
+ // If a filter is given (and it is not just "TRUE") - then use it
to perform run-time pruning
+ //
+ if ( filterExpr != null && ! (filterExpr instanceof
ValueExpressions.BooleanExpression) ) { // skip when no filter or filter is
TRUE
+
+ int rowGroupIndex = rowGroup.getRowGroupIndex();
+ long footerRowCount =
footer.getBlocks().get(rowGroupIndex).getRowCount();
+
+ if ( timer != null ) { // restart the timer, if tracing
+ timer.reset();
+ timer.start();
+ }
+
+ // When starting a new file, or at the first time - Initialize
path specific metadata etc
+ if ( ! rowGroup.getPath().equals(prevRowGroupPath) ) {
+ // Get the table metadata (V3)
+ tableMetadataV3 = Metadata.getParquetTableMetadata(footer, fs,
rowGroup.getPath().toString(), readerConfig);
+
+ // The file status for this file
+ FileStatus fileStatus = fs.getFileStatus(rowGroup.getPath());
+ List<FileStatus> listFileStatus = new
ArrayList<>(Arrays.asList(fileStatus));
+ List<Path> listRowGroupPath = new
ArrayList<>(Arrays.asList(rowGroup.getPath()));
+ List<ReadEntryWithPath> entries = new
ArrayList<>(Arrays.asList(new ReadEntryWithPath(rowGroup.getPath())));
+ fileSelection = new FileSelection(listFileStatus,
listRowGroupPath, selectionRoot);
+
+ metadataProvider = new ParquetTableMetadataProviderImpl(entries,
selectionRoot, fileSelection.cacheFileRoot, readerConfig, fs,false);
+ // The file metadata (for all columns)
+ fileMetadataV3 =
Metadata.getParquetFileMetadata_v3(tableMetadataV3, footer, fileStatus, fs,
true, null, readerConfig);
+
+ prevRowGroupPath = rowGroup.getPath(); // for next time
+ }
+
+ MetadataBase.RowGroupMetadata rowGroupMetadata =
fileMetadataV3.getRowGroups().get(rowGroup.getRowGroupIndex());
+
+ Map<SchemaPath, ColumnStatistics> columnsStatistics =
ParquetTableMetadataUtils.getRowGroupColumnStatistics(tableMetadataV3,
rowGroupMetadata);
+
+ List<SchemaPath> columns =
columnsStatistics.keySet().stream().collect(Collectors.toList());
+
+ ParquetGroupScan parquetGroupScan = new ParquetGroupScan(
context.getQueryUserName(), metadataProvider, fileSelection, columns,
readerConfig, filterExpr);
Review comment:
Creating a new instance of the ParquetGroupScan seems too much overhead
since this is happening for each row group. I understand how you may have
arrived at this since the run-time does not have access to the planner objects
such as the original ParquetGroupScan. However, the only reason you need this
is to create a FilterPredicate, which is accessible through the
ParquetGroupScan. Could we just create a single (dummy) instance of
ParquetGroupScan using 1 file (or row group) outside the main For loop and just
create the FilterPredicate right in the beginning before even iterating over
all the row groups ? The construction of the FilterPredicate in
`getFilterPredicate()` itself does not seem to have any direct dependence on
any internal state of the ParquetGroupScan as far as I can tell.
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> Run-time row group pruning
> --------------------------
>
> Key: DRILL-7062
> URL: https://issues.apache.org/jira/browse/DRILL-7062
> Project: Apache Drill
> Issue Type: Sub-task
> Components: Metadata
> Reporter: Venkata Jyothsna Donapati
> Assignee: Boaz Ben-Zvi
> Priority: Major
> Fix For: 1.16.0
>
> Original Estimate: 504h
> Remaining Estimate: 504h
>
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