cryptoe commented on code in PR #15987:
URL: https://github.com/apache/druid/pull/15987#discussion_r1512655681
##########
processing/src/main/java/org/apache/druid/frame/allocation/HeapMemoryAllocator.java:
##########
@@ -53,7 +53,7 @@ public static HeapMemoryAllocator unlimited()
@Override
public Optional<ResourceHolder<WritableMemory>> allocate(final long size)
{
- if (bytesAllocated < capacity - size) {
+ if (size <= capacity - bytesAllocated) {
Review Comment:
hmm can we have some tests cases which check this ?
##########
processing/src/main/java/org/apache/druid/query/scan/ScanResultValueFramesIterable.java:
##########
@@ -0,0 +1,319 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.druid.query.scan;
+
+import com.google.common.base.Function;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Lists;
+import org.apache.druid.error.DruidException;
+import org.apache.druid.frame.Frame;
+import org.apache.druid.frame.FrameType;
+import org.apache.druid.frame.allocation.MemoryAllocatorFactory;
+import org.apache.druid.frame.write.FrameWriter;
+import org.apache.druid.frame.write.FrameWriterFactory;
+import org.apache.druid.frame.write.FrameWriterUtils;
+import org.apache.druid.frame.write.FrameWriters;
+import org.apache.druid.java.util.common.Pair;
+import org.apache.druid.java.util.common.guava.Sequence;
+import org.apache.druid.java.util.common.io.Closer;
+import org.apache.druid.query.FrameSignaturePair;
+import org.apache.druid.query.IterableRowsCursorHelper;
+import org.apache.druid.segment.Cursor;
+import org.apache.druid.segment.column.RowSignature;
+
+import java.io.Closeable;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.NoSuchElementException;
+
+/**
+ * Returns a thread-unsafe iterable, that converts a sequence of {@link
ScanResultValue} to an iterable of {@link FrameSignaturePair}.
+ * ScanResultValues can have heterogenous row signatures, and the returned
sequence would have batched
+ * them into frames appropriately.
+ * <p>
+ * The batching process greedily merges the values from the scan result values
that have the same signature, while
+ * still maintaining the manageable frame sizes that is determined by the
memory allocator by splitting the rows
+ * whenever necessary.
+ * <p>
+ * It is necessary that we don't batch and store the ScanResultValues
somewhere (like a List) while we do this processing
+ * to prevent the heap from exhausting, without limit. It has to be done
online - as the scan result values get materialized,
+ * we produce frames. A few ScanResultValues might be stored however (if the
frame got cut off in the middle)
+ * <p>
+ * Assuming that we have a sequence of scan result values like:
+ * <p>
+ * ScanResultValue1 - RowSignatureA - 3 rows
+ * ScanResultValue2 - RowSignatureB - 2 rows
+ * ScanResultValue3 - RowSignatureA - 1 rows
+ * ScanResultValue4 - RowSignatureA - 4 rows
+ * ScanResultValue5 - RowSignatureB - 3 rows
+ * <p>
+ * Also, assume that each individual frame can hold two rows (in practice, it
is determined by the row size and
+ * the memory block allocated by the memory allocator factory)
+ * <p>
+ * The output would be a sequence like:
+ * Frame1 - RowSignatureA - rows 1-2 from ScanResultValue1
+ * Frame2 - RowSignatureA - row 3 from ScanResultValue1
+ * Frame3 - RowSignatureB - rows 1-2 from ScanResultValue2
+ * Frame4 - RowSignatureA - row 1 from ScanResultValue3, row 1 from
ScanResultValue4
+ * Frame5 - RowSignatureA - row 2-3 from ScanResultValue4
+ * Frame6 - RowSignatureA - row 4 from ScanResultValue4
+ * Frame7 - RowSignatureB - row 1-2 from ScanResultValue5
+ * Frame8 - RowSignatureB - row 3 from ScanResultValue6
+ * <p>
+ * TODO(laksh): What if single scan result value, and empty
Review Comment:
Hey Found a todo here. In case of a singleScanResult null value, we should
return a nil frame no ?
##########
server/src/main/java/org/apache/druid/server/ClientQuerySegmentWalker.java:
##########
@@ -831,6 +826,31 @@ private static <T, QueryType extends Query<T>> DataSource
materializeResultsAsAr
return InlineDataSource.fromIterable(resultList, signature);
}
+ private static String byteLimitExceededMessage(final long memoryLimit)
+ {
+ return org.apache.druid.java.util.common.StringUtils.format(
+ "Cannot issue the query, subqueries generated results beyond maximum[%d]
bytes. Increase the "
+ + "JVM's memory or set the '%s' in the query context carefully to increase
the space allocated for subqueries to "
Review Comment:
Same comment for clarifying carefully here.
##########
processing/src/main/java/org/apache/druid/frame/allocation/AppendableMemory.java:
##########
@@ -136,7 +136,7 @@ public boolean reserveAdditional(final int bytes)
// Allocation needed.
// Math.max(allocationSize, bytes) in case "bytes" is greater than
SOFT_MAXIMUM_ALLOCATION_SIZE.
final Optional<ResourceHolder<WritableMemory>> newMemory =
- allocator.allocate(Math.max(nextAllocationSize, bytes));
+ allocator.allocate(Math.min(allocator.available(),
Math.max(nextAllocationSize, bytes)));
Review Comment:
* Could you please explain this statement.
If you look at line 129, we are 100% sure that
(bytes<=alllocator.avalable()) so why would be allocate a new chunk which is
exactly same as allocate.available().
We should never go more than the bytes required rite?
NextAllocationSize is more of minCheck.
##########
server/src/main/java/org/apache/druid/server/ClientQuerySegmentWalker.java:
##########
@@ -670,8 +671,14 @@ private static <T, QueryType extends Query<T>> DataSource
toInlineDataSource(
if (limitAccumulator.get() >= rowLimitToUse) {
subqueryStatsProvider.incrementQueriesExceedingRowLimit();
throw ResourceLimitExceededException.withMessage(
- "Cannot issue the query, subqueries generated results beyond
maximum[%d] rows",
- rowLimitToUse
+ "Cannot issue the query, subqueries generated results beyond
maximum[%d] rows. Try setting the"
+ + "%s in the query context to '%s' for enabling byte based
limit, which chooses an optimal limit based on "
+ + "memory size and result's heap usage or manually configure the
values of either %s or %s in the query context",
Review Comment:
We should also mention that this limit should be carefully set since it can
be afftect other queries on the broker and can potentially lead to OOM.
##########
processing/src/main/java/org/apache/druid/query/scan/ScanResultValueFramesIterable.java:
##########
@@ -0,0 +1,319 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.druid.query.scan;
+
+import com.google.common.base.Function;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Lists;
+import org.apache.druid.error.DruidException;
+import org.apache.druid.frame.Frame;
+import org.apache.druid.frame.FrameType;
+import org.apache.druid.frame.allocation.MemoryAllocatorFactory;
+import org.apache.druid.frame.write.FrameWriter;
+import org.apache.druid.frame.write.FrameWriterFactory;
+import org.apache.druid.frame.write.FrameWriterUtils;
+import org.apache.druid.frame.write.FrameWriters;
+import org.apache.druid.java.util.common.Pair;
+import org.apache.druid.java.util.common.guava.Sequence;
+import org.apache.druid.java.util.common.io.Closer;
+import org.apache.druid.query.FrameSignaturePair;
+import org.apache.druid.query.IterableRowsCursorHelper;
+import org.apache.druid.segment.Cursor;
+import org.apache.druid.segment.column.RowSignature;
+
+import java.io.Closeable;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.NoSuchElementException;
+
+/**
+ * Returns a thread-unsafe iterable, that converts a sequence of {@link
ScanResultValue} to an iterable of {@link FrameSignaturePair}.
+ * ScanResultValues can have heterogenous row signatures, and the returned
sequence would have batched
+ * them into frames appropriately.
+ * <p>
+ * The batching process greedily merges the values from the scan result values
that have the same signature, while
+ * still maintaining the manageable frame sizes that is determined by the
memory allocator by splitting the rows
+ * whenever necessary.
+ * <p>
+ * It is necessary that we don't batch and store the ScanResultValues
somewhere (like a List) while we do this processing
+ * to prevent the heap from exhausting, without limit. It has to be done
online - as the scan result values get materialized,
+ * we produce frames. A few ScanResultValues might be stored however (if the
frame got cut off in the middle)
+ * <p>
+ * Assuming that we have a sequence of scan result values like:
+ * <p>
+ * ScanResultValue1 - RowSignatureA - 3 rows
+ * ScanResultValue2 - RowSignatureB - 2 rows
+ * ScanResultValue3 - RowSignatureA - 1 rows
+ * ScanResultValue4 - RowSignatureA - 4 rows
+ * ScanResultValue5 - RowSignatureB - 3 rows
+ * <p>
+ * Also, assume that each individual frame can hold two rows (in practice, it
is determined by the row size and
+ * the memory block allocated by the memory allocator factory)
+ * <p>
+ * The output would be a sequence like:
+ * Frame1 - RowSignatureA - rows 1-2 from ScanResultValue1
+ * Frame2 - RowSignatureA - row 3 from ScanResultValue1
+ * Frame3 - RowSignatureB - rows 1-2 from ScanResultValue2
+ * Frame4 - RowSignatureA - row 1 from ScanResultValue3, row 1 from
ScanResultValue4
+ * Frame5 - RowSignatureA - row 2-3 from ScanResultValue4
+ * Frame6 - RowSignatureA - row 4 from ScanResultValue4
+ * Frame7 - RowSignatureB - row 1-2 from ScanResultValue5
+ * Frame8 - RowSignatureB - row 3 from ScanResultValue6
+ * <p>
+ * TODO(laksh): What if single scan result value, and empty
+ */
+
+public class ScanResultValueFramesIterable implements
Iterable<FrameSignaturePair>
+{
+
+ final Sequence<ScanResultValue> resultSequence;
+ final MemoryAllocatorFactory memoryAllocatorFactory;
+ final boolean useNestedForUnknownTypes;
+ final RowSignature defaultRowSignature;
+ final Function<RowSignature, Function<?, Object[]>> resultFormatMapper;
+
+ public ScanResultValueFramesIterable(
+ Sequence<ScanResultValue> resultSequence,
+ MemoryAllocatorFactory memoryAllocatorFactory,
+ boolean useNestedForUnknownTypes,
+ RowSignature defaultRowSignature,
+ Function<RowSignature, Function<?, Object[]>> resultFormatMapper
+ )
+ {
+ this.resultSequence = resultSequence;
+ this.memoryAllocatorFactory = memoryAllocatorFactory;
+ this.useNestedForUnknownTypes = useNestedForUnknownTypes;
+ this.defaultRowSignature = defaultRowSignature;
+ this.resultFormatMapper = resultFormatMapper;
+ }
+
+ @Override
+ public Iterator<FrameSignaturePair> iterator()
+ {
+ return new ScanResultValueFramesIterator(
+ resultSequence,
+ memoryAllocatorFactory,
+ useNestedForUnknownTypes,
+ defaultRowSignature,
+ resultFormatMapper
+ );
+ }
+
+ private static class ScanResultValueFramesIterator implements
Iterator<FrameSignaturePair>
+ {
+
+ /**
+ * Memory allocator factory to use for frame writers
+ */
+ final MemoryAllocatorFactory memoryAllocatorFactory;
+
+ /**
+ * Replace unknown types in the row signature with {@code COMPLEX<JSON>}
+ */
+ final boolean useNestedForUnknownTypes;
+
+ /**
+ * Default row signature to use if the scan result value doesn't cantain
any row signature. This will usually be
+ * the row signature of the scan query containing only the column names
(and no types)
+ */
+ final RowSignature defaultRowSignature;
+
+ /**
+ * Mapper to convert the scan result value to rows
+ */
+ final Function<RowSignature, Function<?, Object[]>> resultFormatMapper;
+
+ /**
+ * Accumulating the closers for all the resources created so far
+ */
+ final Closer closer = Closer.create();
+
+ /**
+ * Iterator from the scan result value's sequence, so that we can fetch
the individual values. Closer registers the
+ * iterator so that we can clean up any resources held by the sequence's
iterator, and prevent leaking
+ */
+ final ScanResultValueIterator resultSequenceIterator;
+
+ /**
+ * Either null, or points to the current non-empty cursor (and the cursor
would point to the current row)
+ */
+ Cursor currentCursor = null;
+
+ /**
+ * Row signature of the current row
+ */
+ RowSignature currentRowSignature = null;
+
+
+ public ScanResultValueFramesIterator(
+ Sequence<ScanResultValue> resultSequence,
+ MemoryAllocatorFactory memoryAllocatorFactory,
+ boolean useNestedForUnknownTypes,
+ RowSignature defaultRowSignature,
+ Function<RowSignature, Function<?, Object[]>> resultFormatMapper
+ )
+ {
+ this.memoryAllocatorFactory = memoryAllocatorFactory;
+ this.useNestedForUnknownTypes = useNestedForUnknownTypes;
+ this.defaultRowSignature = defaultRowSignature;
+ this.resultFormatMapper = resultFormatMapper;
+ this.resultSequenceIterator = new
ScanResultValueIterator(resultSequence);
+
+ closer.register(resultSequenceIterator);
+
+ // Makes sure that we run through all the empty scan result values at
the beginning and are pointing to a valid
+ // row
+ populateCursor();
+ }
+
+ @Override
+ public boolean hasNext()
+ {
+ return !done();
+ }
+
+ @Override
+ public FrameSignaturePair next()
+ {
+ if (!hasNext()) {
+ throw new NoSuchElementException("No more frames to produce. Call
`hasNext()` before calling `next()`");
+ }
+
+ // It would ensure that the cursor and the currentRowSignature is
populated properly before we
+ // start all the processing
+ populateCursor();
+ boolean firstRowWritten = false;
+ // While calling populateCursor() repeatedly, currentRowSignature might
change. Therefore we store the signature
+ // with which we have written the frames
+ final RowSignature writtenSignature = currentRowSignature;
+ FrameWriterFactory frameWriterFactory =
FrameWriters.makeFrameWriterFactory(
+ FrameType.COLUMNAR,
+ memoryAllocatorFactory,
+ currentRowSignature,
+ Collections.emptyList()
+ );
+ Frame frame;
+ try (final FrameWriter frameWriter =
frameWriterFactory.newFrameWriter(new SettableCursorColumnSelectorFactory(
+ () -> currentCursor,
+ currentRowSignature
+ ))) {
+ while (populateCursor()) { // Do till we don't have any more rows, or
the next row isn't compatible with the current row
Review Comment:
This should also mention that we need to create a new frame if the current
frame is out of space no ?
##########
processing/src/main/java/org/apache/druid/frame/segment/FrameCursorUtils.java:
##########
@@ -79,60 +79,71 @@ public static Filter buildFilter(@Nullable Filter filter,
Interval interval)
/**
* Writes a {@link Cursor} to a sequence of {@link Frame}. This method
iterates over the rows of the cursor,
- * and writes the columns to the frames
- *
- * @param cursor Cursor to write to the frame
- * @param frameWriterFactory Frame writer factory to write to the frame.
- * Determines the signature of the rows that
are written to the frames
+ * and writes the columns to the frames. The iterable is lazy, and it
traverses the required portion of the cursor
+ * as required
*/
- public static Sequence<Frame> cursorToFrames(
- Cursor cursor,
- FrameWriterFactory frameWriterFactory
+ public static Iterable<Frame> cursorToFramesIterable(
+ final Cursor cursor,
+ final FrameWriterFactory frameWriterFactory
)
{
+ return () -> new Iterator<Frame>()
+ {
+ @Override
+ public boolean hasNext()
+ {
+ return !cursor.isDone();
+ }
- return Sequences.simple(
- () -> new Iterator<Frame>()
- {
- @Override
- public boolean hasNext()
- {
- return !cursor.isDone();
- }
-
- @Override
- public Frame next()
- {
- // Makes sure that cursor contains some elements prior. This
ensures if no row is written, then the row size
- // is larger than the MemoryAllocators returned by the provided
factory
- if (!hasNext()) {
- throw new NoSuchElementException();
+ @Override
+ public Frame next()
+ {
+ // Makes sure that cursor contains some elements prior. This ensures
if no row is written, then the row size
+ // is larger than the MemoryAllocators returned by the provided factory
+ if (!hasNext()) {
+ throw new NoSuchElementException();
+ }
+ boolean firstRowWritten = false;
+ Frame frame;
+ try (final FrameWriter frameWriter =
frameWriterFactory.newFrameWriter(cursor.getColumnSelectorFactory())) {
+ while (!cursor.isDone()) {
+ if (!frameWriter.addSelection()) {
+ break;
}
- boolean firstRowWritten = false;
- Frame frame;
- try (final FrameWriter frameWriter =
frameWriterFactory.newFrameWriter(cursor.getColumnSelectorFactory())) {
- while (!cursor.isDone()) {
- if (!frameWriter.addSelection()) {
- break;
- }
- firstRowWritten = true;
- cursor.advance();
- }
-
- if (!firstRowWritten) {
- throw DruidException
- .forPersona(DruidException.Persona.DEVELOPER)
- .ofCategory(DruidException.Category.CAPACITY_EXCEEDED)
- .build("Subquery's row size exceeds the frame size and
therefore cannot write the subquery's "
- + "row to the frame. This is a non-configurable
static limit that can only be modified by the "
- + "developer.");
- }
+ firstRowWritten = true;
+ cursor.advance();
+ }
- frame = Frame.wrap(frameWriter.toByteArray());
- }
- return frame;
+ if (!firstRowWritten) {
+ throw DruidException
+ .forPersona(DruidException.Persona.DEVELOPER)
+ .ofCategory(DruidException.Category.CAPACITY_EXCEEDED)
+ .build("Subquery's row size exceeds the frame size and
therefore cannot write the subquery's "
Review Comment:
We should mention here that a single row size exceeds the frameSize limit of
`xxx`. We should also mention the corrective action.
If the user is hitting into this limit, they should change the input data
with either smaller rows or change the query in such a way that does not read
particularly fat columns.
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