velox-configuration.md

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layout: page title: Configuration nav_order: 16

Gluten Velox backend configurations

Key	Modifiability	Default	Description
spark.gluten.sql.columnar.backend.velox.IOThreads	⚓ Static	<undefined>	The Size of the IO thread pool in the Connector. This thread pool is used for split preloading and DirectBufferedInput. By default, the value is the same as the maximum task slots per Spark executor.
spark.gluten.sql.columnar.backend.velox.SplitPreloadPerDriver	🔄 Dynamic	2	The split preload per task
spark.gluten.sql.columnar.backend.velox.abandonPartialAggregationMinPct	🔄 Dynamic	90	If partial aggregation aggregationPct greater than this value, partial aggregation may be early abandoned. Note: this option only works when flushable partial aggregation is enabled. Ignored when spark.gluten.sql.columnar.backend.velox.flushablePartialAggregation=false.
spark.gluten.sql.columnar.backend.velox.abandonPartialAggregationMinRows	🔄 Dynamic	100000	If partial aggregation input rows number greater than this value, partial aggregation may be early abandoned. Note: this option only works when flushable partial aggregation is enabled. Ignored when spark.gluten.sql.columnar.backend.velox.flushablePartialAggregation=false.
spark.gluten.sql.columnar.backend.velox.asyncTimeoutOnTaskStopping	⚓ Static	30000ms	Timeout in milliseconds when waiting for runtime-scoped async work to finish during teardown.
spark.gluten.sql.columnar.backend.velox.cacheEnabled	⚓ Static	false	Enable Velox cache, default off. It's recommended to enablesoft-affinity as well when enable velox cache.
spark.gluten.sql.columnar.backend.velox.cachePrefetchMinPct	⚓ Static	0	Set prefetch cache min pct for velox file scan
spark.gluten.sql.columnar.backend.velox.checkUsageLeak	⚓ Static	true	Enable check memory usage leak.
spark.gluten.sql.columnar.backend.velox.cudf.batchSize	🔄 Dynamic	2147483647	Cudf input batch size after shuffle reader
spark.gluten.sql.columnar.backend.velox.cudf.enableTableScan	⚓ Static	false	Enable cudf table scan
spark.gluten.sql.columnar.backend.velox.cudf.enableValidation	⚓ Static	true	Heuristics you can apply to validate a cuDF/GPU plan and only offload when the entire stage can be fully and profitably executed on GPU
spark.gluten.sql.columnar.backend.velox.cudf.memoryPercent	⚓ Static	50	The initial percent of GPU memory to allocate for memory resource for one thread.
spark.gluten.sql.columnar.backend.velox.cudf.memoryResource	⚓ Static	async	GPU RMM memory resource.
spark.gluten.sql.columnar.backend.velox.cudf.shuffleMaxPrefetchBytes	🔄 Dynamic	1028MB	Maximum bytes to prefetch in CPU memory during GPU shuffle read while waiting for GPU available.
spark.gluten.sql.columnar.backend.velox.directorySizeGuess	⚓ Static	32KB	Deprecated, rename to spark.gluten.sql.columnar.backend.velox.footerEstimatedSize
spark.gluten.sql.columnar.backend.velox.enableTimestampNtzValidation	🔄 Dynamic	true	Enable validation fallback for TimestampNTZ type. When true (default), any plan containing TimestampNTZ will fall back to Spark execution. Set to false during development/testing of TimestampNTZ support to allow native execution.
spark.gluten.sql.columnar.backend.velox.fileHandleCacheEnabled	⚓ Static	false	Disables caching if false. File handle cache should be disabled if files are mutable, i.e. file content may change while file path stays the same.
spark.gluten.sql.columnar.backend.velox.filePreloadThreshold	⚓ Static	1MB	Set the file preload threshold for velox file scan, refer to Velox's file-preload-threshold
spark.gluten.sql.columnar.backend.velox.floatingPointMode	🔄 Dynamic	loose	Config used to control the tolerance of floating point operations alignment with Spark. When the mode is set to strict, flushing is disabled for sum(float/double)and avg(float/double). When set to loose, flushing will be enabled.
spark.gluten.sql.columnar.backend.velox.flushablePartialAggregation	🔄 Dynamic	true	Enable flushable aggregation. If true, Gluten will try converting regular aggregation into Velox's flushable aggregation when applicable. A flushable aggregation could emit intermediate result at anytime when memory is full / data reduction ratio is low.
spark.gluten.sql.columnar.backend.velox.footerEstimatedSize	⚓ Static	32KB	Set the footer estimated size for velox file scan, refer to Velox's footer-estimated-size
spark.gluten.sql.columnar.backend.velox.hashProbe.bloomFilterPushdown.maxSize	🔄 Dynamic	0b	The maximum byte size of Bloom filter that can be generated from hash probe. When set to 0, no Bloom filter will be generated. To achieve optimal performance, this should not be too larger than the CPU cache size on the host.
spark.gluten.sql.columnar.backend.velox.hashProbe.dynamicFilterPushdown.enabled	🔄 Dynamic	true	Whether hash probe can generate any dynamic filter (including Bloom filter) and push down to upstream operators.
spark.gluten.sql.columnar.backend.velox.hashShuffle.reader.streamMerge.enabled	🔄 Dynamic	false	Enables a reader-side raw payload merge fast path for plain hash shuffle payloads within each shuffle input stream. This path merges payload buffers before Velox vectors are materialized, so it has lower per-batch overhead than generic VeloxResizeBatchesExec resizing, but it only covers plain payloads. Complex types and dictionary-encoded payloads are not merged by this path. VeloxResizeBatchesExec can still be enabled separately as a generic complement for types and encodings not covered by this fast path. If false, each hash shuffle payload is returned as its own columnar batch.
spark.gluten.sql.columnar.backend.velox.loadQuantum	⚓ Static	256MB	Set the load quantum for velox file scan, recommend to use the default value (256MB) for performance consideration. If Velox cache is enabled, it can be 8MB at most.
spark.gluten.sql.columnar.backend.velox.maxCoalescedBytes	⚓ Static	64MB	Set the max coalesced bytes for velox file scan
spark.gluten.sql.columnar.backend.velox.maxCoalescedDistance	⚓ Static	512KB	Set the max coalesced distance bytes for velox file scan
spark.gluten.sql.columnar.backend.velox.maxCompiledRegexes	🔄 Dynamic	100	Controls maximum number of compiled regular expression patterns per function instance per thread of execution.
spark.gluten.sql.columnar.backend.velox.maxExtendedPartialAggregationMemory	🔄 Dynamic	<undefined>	Set the max extended memory of partial aggregation in bytes. When this option is set to a value greater than 0, it will override spark.gluten.sql.columnar.backend.velox.maxExtendedPartialAggregationMemoryRatio. Note: this option only works when flushable partial aggregation is enabled. Ignored when spark.gluten.sql.columnar.backend.velox.flushablePartialAggregation=false.
spark.gluten.sql.columnar.backend.velox.maxExtendedPartialAggregationMemoryRatio	🔄 Dynamic	0.15	Set the max extended memory of partial aggregation as maxExtendedPartialAggregationMemoryRatio of offheap size. Note: this option only works when flushable partial aggregation is enabled. Ignored when spark.gluten.sql.columnar.backend.velox.flushablePartialAggregation=false.
spark.gluten.sql.columnar.backend.velox.maxPartialAggregationMemory	🔄 Dynamic	<undefined>	Set the max memory of partial aggregation in bytes. When this option is set to a value greater than 0, it will override spark.gluten.sql.columnar.backend.velox.maxPartialAggregationMemoryRatio. Note: this option only works when flushable partial aggregation is enabled. Ignored when spark.gluten.sql.columnar.backend.velox.flushablePartialAggregation=false.
spark.gluten.sql.columnar.backend.velox.maxPartialAggregationMemoryRatio	🔄 Dynamic	0.1	Set the max memory of partial aggregation as maxPartialAggregationMemoryRatio of offheap size. Note: this option only works when flushable partial aggregation is enabled. Ignored when spark.gluten.sql.columnar.backend.velox.flushablePartialAggregation=false.
spark.gluten.sql.columnar.backend.velox.maxPartitionsPerWritersSession	🔄 Dynamic	10000	Maximum number of partitions per a single table writer instance.
spark.gluten.sql.columnar.backend.velox.maxSpillBytes	🔄 Dynamic	100G	The maximum file size of a query
spark.gluten.sql.columnar.backend.velox.maxSpillFileSize	🔄 Dynamic	1GB	The maximum size of a single spill file created
spark.gluten.sql.columnar.backend.velox.maxSpillLevel	🔄 Dynamic	4	The max allowed spilling level with zero being the initial spilling level
spark.gluten.sql.columnar.backend.velox.maxSpillRunRows	🔄 Dynamic	3M	The maximum row size of a single spill run
spark.gluten.sql.columnar.backend.velox.maxTargetFileSize	🔄 Dynamic	0b	The target file size for each output file when writing data. 0 means no limit on target file size, and the actual file size will be determined by other factors such as max partition number and shuffle batch size.
spark.gluten.sql.columnar.backend.velox.memCacheSize	⚓ Static	1GB	The memory cache size
spark.gluten.sql.columnar.backend.velox.memInitCapacity	🔄 Dynamic	8MB	The initial memory capacity to reserve for a newly created Velox query memory pool.
spark.gluten.sql.columnar.backend.velox.memoryPoolCapacityTransferAcrossTasks	🔄 Dynamic	true	Whether to allow memory capacity transfer between memory pools from different tasks.
spark.gluten.sql.columnar.backend.velox.memoryUseHugePages	🔄 Dynamic	false	Use explicit huge pages for Velox memory allocation.
spark.gluten.sql.columnar.backend.velox.orc.scan.enabled	🔄 Dynamic	true	Enable velox orc scan. If disabled, vanilla spark orc scan will be used.
spark.gluten.sql.columnar.backend.velox.orcUseColumnNames	🔄 Dynamic	true	Maps table field names to file field names using names, not indices for ORC files.
spark.gluten.sql.columnar.backend.velox.parquet.pageSizeBytes	🔄 Dynamic	1MB	The page size in bytes is for compression.
spark.gluten.sql.columnar.backend.velox.parquetUseColumnNames	🔄 Dynamic	true	Maps table field names to file field names using names, not indices for Parquet files.
spark.gluten.sql.columnar.backend.velox.prefetchRowGroups	⚓ Static	1	Set the prefetch row groups for velox file scan
spark.gluten.sql.columnar.backend.velox.queryTraceEnabled	🔄 Dynamic	false	Enable query tracing flag.
spark.gluten.sql.columnar.backend.velox.reclaimMaxWaitMs	🔄 Dynamic	3600000ms	The max time in ms to wait for memory reclaim.
spark.gluten.sql.columnar.backend.velox.resizeBatches.copyRanges.enabled	🔄 Dynamic	true	Enables a VeloxResizeBatchesExec fast path that combines eligible batches using Velox vector copyRanges instead of generic RowVector append. When possible, it collects the small input batches for one VeloxResizeBatchesExec output, allocates the output RowVector once, and bulk-copies child vector ranges. This is most useful for shuffle-read outputs where plain hash shuffle payloads are materialized as dense flat vectors. Complex vectors can also use copyRanges, but ARRAY and MAP still rebuild nested offsets and sizes while bulk-copying child ranges. Unsupported encodings such as dictionary and constant vectors fall back to the generic copy path. This option is enabled by default and complements the reader-side raw payload merge fast path: that path avoids materializing small plain payload batches, while this option optimizes VeloxResizeBatchesExec when that operator is enabled.
spark.gluten.sql.columnar.backend.velox.resizeBatches.shuffleInput	🔄 Dynamic	true	If true, combine small columnar batches together before sending to shuffle. The default minimum output batch size is equal to 0.25 * spark.gluten.sql.columnar.maxBatchSize
spark.gluten.sql.columnar.backend.velox.resizeBatches.shuffleInput.minSize	🔄 Dynamic	<undefined>	The minimum batch size for shuffle. If size of an input batch is smaller than the value, it will be combined with other batches before sending to shuffle. Only functions when spark.gluten.sql.columnar.backend.velox.resizeBatches.shuffleInput is set to true. Default value: 0.25 *
spark.gluten.sql.columnar.backend.velox.resizeBatches.shuffleInputOutput.minSize	🔄 Dynamic	<undefined>	The minimum batch size for shuffle input and output. If size of an input batch is smaller than the value, it will be combined with other batches before sending to shuffle. The same applies for batches output by shuffle read. Only functions when spark.gluten.sql.columnar.backend.velox.resizeBatches.shuffleInput or spark.gluten.sql.columnar.backend.velox.resizeBatches.shuffleOutput is set to true. Default value: 0.25 *
spark.gluten.sql.columnar.backend.velox.resizeBatches.shuffleOutput	🔄 Dynamic	false	If true, combine small columnar batches together right after shuffle read. The default minimum output batch size is equal to 0.25 * spark.gluten.sql.columnar.maxBatchSize
spark.gluten.sql.columnar.backend.velox.showTaskMetricsWhenFinished	🔄 Dynamic	false	Show velox full task metrics when finished.
spark.gluten.sql.columnar.backend.velox.spillFileSystem	🔄 Dynamic	local	The filesystem used to store spill data. local: The local file system. heap-over-local: Write file to JVM heap if having extra heap space. Otherwise write to local file system.
spark.gluten.sql.columnar.backend.velox.spillStrategy	🔄 Dynamic	auto	none: Disable spill on Velox backend; auto: Let Spark memory manager manage Velox's spilling
spark.gluten.sql.columnar.backend.velox.ssdCacheIOThreads	⚓ Static	1	The IO threads for cache promoting
spark.gluten.sql.columnar.backend.velox.ssdCachePath	⚓ Static	/tmp	The folder to store the cache files, better on SSD
spark.gluten.sql.columnar.backend.velox.ssdCacheShards	⚓ Static	1	The cache shards
spark.gluten.sql.columnar.backend.velox.ssdCacheSize	⚓ Static	1GB	The SSD cache size, will do memory caching only if this value = 0
spark.gluten.sql.columnar.backend.velox.ssdCheckpointIntervalBytes	⚓ Static	0	Checkpoint after every 'checkpointIntervalBytes' for SSD cache. 0 means no checkpointing.
spark.gluten.sql.columnar.backend.velox.ssdChecksumEnabled	⚓ Static	false	If true, checksum write to SSD is enabled.
spark.gluten.sql.columnar.backend.velox.ssdChecksumReadVerificationEnabled	⚓ Static	false	If true, checksum read verification from SSD is enabled.
spark.gluten.sql.columnar.backend.velox.ssdDisableFileCow	⚓ Static	false	True if copy on write should be disabled.
spark.gluten.sql.columnar.backend.velox.ssdODirect	⚓ Static	false	The O_DIRECT flag for cache writing
spark.gluten.sql.columnar.backend.velox.valueStream.dynamicFilter.enabled	🔄 Dynamic	false	Whether to apply dynamic filters pushed down from hash probe in the ValueStream (shuffle reader) operator to filter rows before they reach the hash join.
spark.gluten.sql.enable.enhancedFeatures	🔄 Dynamic	true	Enable some features including iceberg native write and other features.
spark.gluten.sql.rewrite.castArrayToString	🔄 Dynamic	true	When true, rewrite cast(array as String) to concat('[', array_join(array, ', ', null), ']') to allow offloading to Velox.
spark.gluten.velox.broadcast.build.targetBytesPerThread	⚓ Static	32MB	It is used to calculate the number of hash table build threads. Based on our testing across various thresholds (1MB to 128MB), we recommend a value of 32MB or 64MB, as these consistently provided the most significant performance gains.
spark.gluten.velox.castFromVarcharAddTrimNode	🔄 Dynamic	false	If true, will add a trim node which has the same semantic as vanilla Spark to CAST-from-varchar.Otherwise, do nothing.

Gluten Velox backend experimental configurations

Key	Modifiability	Default	Description
spark.gluten.velox.abandonDedupHashMap.minPct	🔄 Dynamic	0	Experimental: abandon hashmap build if duplicated rows are more than this percentile. Value is integer based and range is [0, 100].
spark.gluten.velox.abandonDedupHashMap.minRows	🔄 Dynamic	100000	Experimental: abandon hashmap build if duplicated rows more than this number.
spark.gluten.velox.joinBuildVectorHasherMaxNumDistinct	🔄 Dynamic	1000000	Experimental: maximum number of distinct values to keep when merging vector hashers in join HashBuild.
spark.gluten.velox.minTableRowsForParallelJoinBuild	🔄 Dynamic	1000	Experimental: the minimum number of table rows that can trigger the parallel hash join table build.
spark.gluten.velox.offHeapBroadcastBuildRelation.enabled	🔄 Dynamic	false	Experimental: If enabled, broadcast build relation will use offheap memory. Otherwise, broadcast build relation will use onheap memory.