Limit RLE to direct expansion when partitioning

Flushes PositionsAppenderPageBuilder entries if the cost of converting
all RLE channels into direct channels would exceed the maximum page size
by a factor of 8x.

Previously, page builders could buffer a very large number of RLE
positions without being considered full and then suddenly expand to huge
sizes when forced to transition to a direct representation as a result
of the RLE input value changing across one or more columns. In
particular, this is can easily happen when pages are produced from CROSS
JOIN UNNEST operations.

core/trino-main/src/main/java/io/trino/operator/output/PositionsAppenderPageBuilder.java

@@ -13,6 +13,7 @@
  */
 package io.trino.operator.output;
 
+import com.google.common.annotations.VisibleForTesting;
 import io.trino.operator.project.PageProcessor;
 import io.trino.spi.Page;
 import io.trino.spi.block.Block;
@@ -21,31 +22,46 @@
 
 import java.util.List;
 
+import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkState;
 import static java.util.Objects.requireNonNull;
 
 public class PositionsAppenderPageBuilder
 {
     private static final int DEFAULT_INITIAL_EXPECTED_ENTRIES = 8;
+    // Maximum page size before being considered full if all RLE channels convert are converted to direct
+    private static final int MAXIMUM_DIRECT_SIZE_MULTIPLIER = 8;
     private final UnnestingPositionsAppender[] channelAppenders;
     private final int maxPageSizeInBytes;
+    private final int maxDirectPageSizeInBytes;
     private int declaredPositions;
 
     public static PositionsAppenderPageBuilder withMaxPageSize(int maxPageBytes, List<Type> sourceTypes, PositionsAppenderFactory positionsAppenderFactory)
     {
-        return new PositionsAppenderPageBuilder(DEFAULT_INITIAL_EXPECTED_ENTRIES, maxPageBytes, sourceTypes, positionsAppenderFactory);
+        return withMaxPageSize(maxPageBytes, maxPageBytes * MAXIMUM_DIRECT_SIZE_MULTIPLIER, sourceTypes, positionsAppenderFactory);
+    }
+
+    @VisibleForTesting
+    static PositionsAppenderPageBuilder withMaxPageSize(int maxPageBytes, int maxDirectSizeInBytes, List<Type> sourceTypes, PositionsAppenderFactory positionsAppenderFactory)
+    {
+        return new PositionsAppenderPageBuilder(DEFAULT_INITIAL_EXPECTED_ENTRIES, maxPageBytes, maxDirectSizeInBytes, sourceTypes, positionsAppenderFactory);
     }
 
     private PositionsAppenderPageBuilder(
             int initialExpectedEntries,
             int maxPageSizeInBytes,
+            int maxDirectPageSizeInBytes,
             List<? extends Type> types,
             PositionsAppenderFactory positionsAppenderFactory)
     {
         requireNonNull(types, "types is null");
         requireNonNull(positionsAppenderFactory, "positionsAppenderFactory is null");
+        checkArgument(maxPageSizeInBytes > 0, "maxPageSizeInBytes is negative: %s", maxPageSizeInBytes);
+        checkArgument(maxDirectPageSizeInBytes > 0, "maxDirectPageSizeInBytes is negative: %s", maxDirectPageSizeInBytes);
+        checkArgument(maxDirectPageSizeInBytes >= maxPageSizeInBytes, "maxDirectPageSizeInBytes (%s) must be >= maxPageSizeInBytes (%s)", maxDirectPageSizeInBytes, maxPageSizeInBytes);
 
         this.maxPageSizeInBytes = maxPageSizeInBytes;
+        this.maxDirectPageSizeInBytes = maxDirectPageSizeInBytes;
         channelAppenders = new UnnestingPositionsAppender[types.size()];
         for (int i = 0; i < channelAppenders.length; i++) {
             channelAppenders[i] = positionsAppenderFactory.create(types.get(i), initialExpectedEntries, maxPageSizeInBytes);
@@ -92,14 +108,23 @@ public long getSizeInBytes()
         return sizeInBytes;
     }
 
+    public long getDirectSizeInBytes()
+    {
+        long directSizeInBytes = 0;
+        for (UnnestingPositionsAppender positionsAppender : channelAppenders) {
+            directSizeInBytes += positionsAppender.getDirectSizeInBytes();
+        }
+        return directSizeInBytes;
+    }
+
     private void declarePositions(int positions)
     {
         declaredPositions += positions;
     }
 
     public boolean isFull()
     {
-        return declaredPositions >= PageProcessor.MAX_BATCH_SIZE || getSizeInBytes() >= maxPageSizeInBytes;
+        return declaredPositions >= PageProcessor.MAX_BATCH_SIZE || getSizeInBytes() >= maxPageSizeInBytes || getDirectSizeInBytes() >= maxDirectPageSizeInBytes;
     }
 
     public boolean isEmpty()

core/trino-main/src/main/java/io/trino/operator/output/UnnestingPositionsAppender.java

@@ -211,6 +211,11 @@ public long getSizeInBytes()
                 (rleValue != null ? rleValue.getSizeInBytes() : 0);
     }
 
+    public long getDirectSizeInBytes()
+    {
+        return rleValue == null ? getSizeInBytes() : (rleValue.getSizeInBytes() * rlePositionCount);
+    }
+
     private static class DictionaryIdsBuilder
     {
         private static final int INSTANCE_SIZE = instanceSize(DictionaryIdsBuilder.class);

core/trino-main/src/test/java/io/trino/operator/output/TestPositionsAppenderPageBuilder.java

@@ -0,0 +1,101 @@
+/*
+ * Licensed 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 io.trino.operator.output;
+
+import io.airlift.slice.Slices;
+import io.trino.operator.project.PageProcessor;
+import io.trino.spi.Page;
+import io.trino.spi.block.Block;
+import io.trino.spi.block.RunLengthEncodedBlock;
+import io.trino.type.BlockTypeOperators;
+import it.unimi.dsi.fastutil.ints.IntArrayList;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static io.trino.spi.type.VarcharType.VARCHAR;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class TestPositionsAppenderPageBuilder
+{
+    @Test
+    public void testFullOnPositionCountLimit()
+    {
+        int maxPageBytes = 1024 * 1024;
+        int maxDirectSize = maxPageBytes * 10;
+        PositionsAppenderPageBuilder pageBuilder = PositionsAppenderPageBuilder.withMaxPageSize(
+                maxPageBytes,
+                maxDirectSize,
+                List.of(VARCHAR),
+                new PositionsAppenderFactory(new BlockTypeOperators()));
+
+        Block rleBlock = RunLengthEncodedBlock.create(VARCHAR, Slices.utf8Slice("test"), 10);
+        Page inputPage = new Page(rleBlock);
+
+        IntArrayList positions = new IntArrayList();
+        positions.addAll(List.of(0, 1, 2, 3, 4, 5, 6, 7, 8, 9));
+        // Append 8190 positions, just less than PageProcessor.MAX_BATCH_SIZE
+        assertEquals(8192, PageProcessor.MAX_BATCH_SIZE, "expected constant to be 8192");
+        for (int i = 0; i < 819; i++) {
+            pageBuilder.appendToOutputPartition(inputPage, positions);
+        }
+        assertFalse(pageBuilder.isFull(), "pageBuilder should still not be full");
+        // Append 10 more positions, crossing the threshold on position count
+        pageBuilder.appendToOutputPartition(inputPage, positions);
+        assertTrue(pageBuilder.isFull(), "pageBuilder should be full");
+        assertEquals(rleBlock.getSizeInBytes(), pageBuilder.getSizeInBytes());
+        assertTrue(pageBuilder.getDirectSizeInBytes() < maxDirectSize, "direct size should still be below threshold");
+    }
+
+    @Test
+    public void testFullOnDirectSizeInBytes()
+    {
+        int maxPageBytes = 100;
+        int maxDirectSize = 1000;
+        PositionsAppenderPageBuilder pageBuilder = PositionsAppenderPageBuilder.withMaxPageSize(
+                maxPageBytes,
+                maxDirectSize,
+                List.of(VARCHAR),
+                new PositionsAppenderFactory(new BlockTypeOperators()));
+
+        assertEquals(0L, pageBuilder.getSizeInBytes());
+        assertEquals(0L, pageBuilder.getDirectSizeInBytes());
+        assertFalse(pageBuilder.isFull());
+
+        Block rleBlock = RunLengthEncodedBlock.create(VARCHAR, Slices.utf8Slice("test"), 10);
+        Page inputPage = new Page(rleBlock);
+
+        IntArrayList positions = new IntArrayList();
+        positions.addAll(List.of(0, 1, 2, 3, 4, 5, 6, 7, 8, 9));
+        pageBuilder.appendToOutputPartition(inputPage, positions);
+        // 10 positions inserted, size in bytes is still the same since we're in RLE mode but direct size is 10x
+        assertEquals(rleBlock.getSizeInBytes(), pageBuilder.getSizeInBytes());
+        assertEquals(rleBlock.getSizeInBytes() * 10, pageBuilder.getDirectSizeInBytes());
+        assertFalse(pageBuilder.isFull());
+
+        // Keep inserting until the direct size limit is reached
+        while (pageBuilder.getDirectSizeInBytes() < maxDirectSize) {
+            pageBuilder.appendToOutputPartition(inputPage, positions);
+        }
+        // size in bytes is unchanged
+        assertEquals(rleBlock.getSizeInBytes(), pageBuilder.getSizeInBytes());
+        // builder reports full due to maximum size in bytes reached
+        assertTrue(pageBuilder.isFull());
+        Page result = pageBuilder.build();
+        assertEquals(120, result.getPositionCount(), "result positions should be below the 8192 maximum");
+        assertTrue(result.getBlock(0) instanceof RunLengthEncodedBlock, "result block is RLE encoded");
+    }
+}