Cluster and Session

When configuring your SQreamDB environment, you have the option to use flags that apply to either the entire cluster or a specific session. Cluster configuration involve metadata and is persistent. Persistent modifications refer to changes made to a system or component that are saved and retained even after the system is restarted or shut down, allowing the modifications to persist over time. Session flags only apply to a specific session and are not persistent. Changes made using session flags are not visible to other users, and once the session ends, the flags return to their default values.

Setting the flags

Syntax

You may set both cluster and session flags using the following syntax on SQreamDB Acceleration Studio and Console:

Cluster flag syntax:

ALTER SYSTEM SET <flagName>

Session flag syntax:

SET <flagName>

Configuration file

You may set session flags within your Legacy Configuration File.

Flag List

Flag Name	Who May Configure	Cluster / Session	Description	Data Type	Default Value and Value Range
binSizes	SUPERUSER	Session	Sets the custom bin size in the cache to enable high granularity bin control.	string	16,32,64,128,256,512,1024,2048,4096,8192,16384,32768,65536, 131072,262144,524288,1048576,2097152,4194304,8388608,16777216, 33554432,67108864,134217728,268435456,536870912,786432000,107374, 1824,1342177280,1610612736,1879048192,2147483648,2415919104, 2684354560,2952790016,3221225472
cacheEvictionMilliseconds	Anyone	Session	Sets how long the cache stores contents before being flushed. Allowed values: 1-4000000000.	bigint	2000
cacheDiskDir	Anyone	Session	Sets the ondisk directory location for the spool to save files on. Allowed values: Any legal string.	bigint	Any legal string
cacheDiskGB	Anyone	Session	Sets the amount of memory (GB) to be used by Spool on the disk. Allowed values: 0-4000000000.	bigint	128
cachePartitions	Anyone	Session	Sets the number of partitions that the cache is split into. Allowed values: 1-4000000000.	bigint	4
cachePersistentDir	Anyone	Session	Sets the persistent directory location for the spool to save files on. Allowed values: Any legal string.	string	/tmp
cachePersistentGB	Anyone	Session	Sets the amount of data (GB) for the cache to store persistently. Allowed values: 0-4000000000.	bigint	128
cacheRamGB	Anyone	Session	Sets the amount of memory (GB) to be used by Spool InMemory. Allowed values: 0-4000000000.	bigint	16
checkCudaMemory	SUPERUSER	Session	Sets the pad device memory allocations with safety buffers to catch out-of-bounds writes.	boolean	FALSE
clientReconnectionTimeout	Anyone	Cluster	Reconnection time out for the system in seconds.	Integer	30
compilerGetsOnlyUFs	SUPERUSER	Session	Sets the runtime to pass only utility functions names to the compiler.	boolean	FALSE
copyToRestrictUtf8	SUPERUSER	Session	Sets the custom bin size in the cache to enable high granularity bin control.	boolean	FALSE
cpuReduceHashtableSize	SUPERUSER	Session	Sets the hash table size of the CpuReduce.	uint	10000
csvLimitRowLength	SUPERUSER	Cluster	Sets the maximum supported CSV row length. Allowed values: 1-4000000000	uint	100000
cudaMemcpyMaxSizeBytes	SUPERUSER	Session	Sets the chunk size for copying from CPU to GPU. If set to 0, do not divide.	uint	0
CudaMemcpySynchronous	SUPERUSER	Session	Indicates if copying from/to GPU is synchronous.	boolean	FALSE
developerMode	SUPERUSER	Session	Enables modifying R&D flags.	boolean	FALSE
enableDeviceDebugMessages	SUPERUSER	Session	Checks for CUDA errors after producing each chunk.	boolean	FALSE
enableLogDebug	SUPERUSER	Session	Enables creating and logging in the clientLogger_debug file.	boolean	TRUE
enableNvprofMarkers	SUPERUSER	Session	Activates the Nvidia profiler (nvprof) markers.	boolean	FALSE
endLogMessage	SUPERUSER	Session	Appends a string at the end of every log line.	string	EOM
extentStorageFileSizeMB	SUPERUSER	Cluster	Sets the minimum size in mebibytes of extents for table bulk data.	uint	20
externalTableBlobEstimate	?	Session	?	?	?
flipJoinOrder	Anyone	Session	Reorders join to force equijoins and/or equijoins sorted by table size.	boolean	FALSE
gatherMemStat	SUPERUSER	Session	Monitors all pinned allocations and all memcopies to/from device, and prints a report of pinned allocations that were not memcopied to/from the device using the dump_pinned_misses utility function.	boolean	FALSE
increaseChunkSizeBeforeReduce	SUPERUSER	Session	Increases the chunk size to reduce query speed.	boolean	FALSE
increaseMemFactors	SUPERUSER	Session	Adds rechunker before expensive chunk producer.	boolean	TRUE
leveldbWriteBufferSize	SUPERUSER	Session	Sets the buffer size.	uint	524288
logSysLevel	Anyone	Session	Determines the client log level: 0 - L_SYSTEM, 1 - L_FATAL, 2 - L_ERROR, 3 - L_WARN, 4 - L_INFO, 5 - L_DEBUG, 6 - L_TRACE	uint	100000
maxAvgBlobSizeToCompressOnGpu	Anyone	Session	Sets the CPU to compress columns with size above (flag’s value) * (row count).	uint	120
maxPinnedPercentageOfTotalRAM	SUPERUSER	Session	Sets the maximum percentage CPU RAM that pinned memory can use.	uint	70
memMergeBlobOffsetsCount	SUPERUSER	Session	Sets the size of memory used during a query to trigger aborting the server.	uint	0
memoryResetTriggerMB	SUPERUSER	Session	Sets the size of memory used during a query to trigger aborting the server.	uint	0
mtRead	SUPERUSER	Session	Splits large reads to multiple smaller ones and executes them concurrently.	boolean	FALSE
mtReadWorkers	SUPERUSER	Session	Sets the number of workers to handle smaller concurrent reads.	uint	30
orcImplicitCasts	SUPERUSER	Session	Sets the implicit cast in orc files, such as int to tinyint and vice versa.	boolean	TRUE
sessionTag	Anyone	Session	Sets the name of the session tag. Allowed values: Any legal string.	string	Any legal string
spoolMemoryGB	Anyone	Session	Sets the amount of memory (GB) to be used by the server for spooling.	uint	8
statementLockTimeout	SUPERUSER	Session	Sets the timeout (seconds) for acquiring object locks before executing statements.	uint	3
useLegacyDecimalLiterals	SUPERUSER	Session	Interprets decimal literals as Double instead of Numeric. Used to preserve legacy behavior in existing customers.	boolean	FALSE
blockNewVarcharObjects	SUPERUSER	Session	Disables the creation of new tables, views, external tables containing Varchar columns, and the creation of user-defined functions with Varchar arguments or a Varchar return value.	boolean	FALSE
defaultGracefulShutdownTimeoutMinutes	SUPERUSER	Cluster	Used for setting the amount of time to pass before SQream performs a graceful server shutdown. Allowed values - 1-4000000000. Related flags: is_healer_on and healer_max_inactivity_hours	bigint	5
limitQueryMemoryGB	SUPERUSER	Cluster	Prevents a query from processing more memory than the defined value.	uint	100000
queueTimeoutMinutes	Anyone	Session	Terminates queries that have exceeded a predefined time limit in the queue.	integer	Default value: 0. Minimum values: 1 minute. Maximum value: 4320 minutes (72 hours)
QueryTimeoutMinutes	Anyone	Session	Terminates queries that have exceeded a predefined execution time limit, ranging from 1 to 4,320 minutes (72 hours).	integer	0 (no query timeout)