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`
`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`
`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`
`cacheEvictionMilliseconds`	Anyone	Session	Sets how long the cache stores contents before being flushed. Allowed values: 1-4000000000.	bigint	`2000`
`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`
`compilerGetsOnlyUFs`	SUPERUSER	Session	Sets the runtime to pass only utility functions names to the compiler.	boolean	`FALSE`
`clientReconnectionTimeout`	Anyone	Cluster	Reconnection time out for the system in seconds.	Integer	`30`
`copyToRestrictUtf8`	SUPERUSER	Session	Sets the custom bin size in the cache to enable high granularity bin control.	boolean	`FALSE`
`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`
`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`
`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`
`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`
`logClientLevel`	SUPERUSER	Cluster	Used to control which log level should appear in the logs. Value range: `0` - `6`	int	Default value: `4` Acceptable values: `0` - Only SYSTEM level logs `1` - SYSTEM and FATAL `2` - SYSTEM, FATAL, and ERROR level logs `3` - SYSTEM, FATAL, ERROR, and WARNING level logs `4` - SYSTEM, FATAL, ERROR, WARNING, and INFO level logs `5` - SYSTEM, FATAL, ERROR, WARNING, INFO, and DEBUG level logs `6` - SYSTEM, FATAL, ERROR, WARNING, INFO, DEBUG, and TRACE level logs
`logFileRotateTimeFrequency`	SUPERUSER	Cluster	Specifies when the system begins writing to a new log file. SQreamDB recommends using the `logFileRotateTimeFrequency` flag (rather than the `logMaxFilesSizeMB` flag) to configure when a new log file is created, as this flag does not limit the number of log files.	string	`daily`. Acceptable values: `daily`, `weekly`, or `monthly`
`logMaxFilesSizeMB`	SUPERUSER	Cluster	Specifies when the system begins writing to a new log file. When configured with the `logMaxFilesSizeMB` flag, the system maintains up to 13 log files. Once the 13th file is complete, the oldest log file is overwritten by the newly created log file. SQreamDB recommends using the `logFileRotateTimeFrequency` flag to configure when a new log file is created, as this flag does not limit the number of log files.	int	`100` (Megabyte)
`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`
`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`
`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)
`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`
`cpuReduceHashtableSize`	SUPERUSER	Session	Sets the hash table size of the CpuReduce.	uint	`10000`
`externalTableBlobEstimate`	?	Session	?	?	?
`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`
`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)