CONNECT System Variables

This page documents system variables related to the CONNECT storage engine. See Server System Variables for a complete list of system variables and instructions on setting them.

See also the Full list of MariaDB options, system and status variables.


  • Description: Java class path
  • Commandline: --connect-class-path=value
  • Scope: Global
  • Dynamic:
  • Data Type: string
  • Default Value:
  • Introduced: Connect 1.04.0006





  • Description: Whether the CONNECT engine should return an exact record number value to information queries. It is OFF by default because this information can take a very long time for large variable record length tables or for remote tables, especially if the remote server is not available. It can be set to ON when exact values are desired, for instance when querying the repartition of rows in a partition table.
  • Commandline: --connect-exact-info=#
  • Scope: Session
  • Dynamic: Yes
  • Data Type: boolean
  • Default Value: OFF
  • Introduced: MariaDB 10.0.15


  • Description: Enable file mapping for index files. To accelerate the indexing process, CONNECT makes an index structure in memory from the index file. This can be done by reading the index file or using it as if it was in memory by “file mapping”. Set to 0 (file read, the default) or 1 (file mapping).
  • Commandline: --connect-indx-map=#
  • Scope: Global
  • Dynamic: Yes
  • Data Type: boolean
  • Default Value: OFF


  • Description: Java wrapper.
  • Commandline: --connect-java-wrapper=val
  • Scope: Global, Session
  • Dynamic: Yes
  • Data Type: string
  • Default Value: wrappers/JdbcInterface
  • Introduced: Connect 1.05.0001, MariaDB 10.2.4


  • Description: Max number of rows for JSON aggregate functions.
  • Commandline: --connect-json-grp-size=#
  • Scope: Global, Session
  • Dynamic: Yes
  • Data Type: numeric
  • Default Value: 10
  • Range: 1 to 2147483647
  • Introduced: MariaDB 10.0.17


  • Description: Representation of JSON null values.
  • Commandline: --connect-json-null=value
  • Scope: Global, Session
  • Dynamic: Yes
  • Data Type: string
  • Default Value: <null>
  • Introduced: MariaDB 10.2.8


  • Description: Path to JVM library.
  • Commandline: --connect-jvm_path=value
  • Scope: Global
  • Dynamic:
  • Data Type: string
  • Default Value:
  • Introduced: Connect 1.04.0006


  • Description: Determines the handling of TEXT columns.
    • NO: The default until Connect 1.06.005, no conversion takes place, and a TYPE_ERROR is returned, resulting in a “not supported” message.
    • YES: The default from Connect 1.06.006. The column is internally converted to a column declared as VARCHAR(n), n being the value of connect_conv_size.
    • FORCE (>= Connect 1.06.006): Also convert ODBC blob columns to TYPE_STRING.
    • SKIP: No conversion. When the column declaration is provided via Discovery (meaning the CONNECT table is created without a column description), this column is not generated. Also applies to ODBC tables.
  • Commandline: --connect-type-conv=#
  • Scope: Session (> MariaDB 10.0.17), Global (<= MariaDB 10.0.16)
  • Dynamic: Yes
  • Data Type: enum
  • Valid Values: NO, YES or SKIP
  • Default Value: YES (>= Connect 1.06.006), NO (<= Connect 1.06.005)


  • Description:
    • NO: The first algorithm is always used. Because it can cause errors when updating variable record length tables, this value should be set only for testing.
    • AUTO: This is the default value. It leaves CONNECT to choose the algorithm to use. Currently it is equivalent to NO, except when updating variable record length tables (DOS, CSV or FMT) with file mapping forced to OFF.
    • YES: Using a temporary file is chosen with some exceptions. These are when file mapping is ON, for VEC tables and when deleting from DBF tables (soft delete). For variable record length tables, file mapping is forced to OFF.
    • FORCE: Like YES but forces file mapping to be OFF for all table types.
    • TEST: Reserved for CONNECT development.
  • Commandline: --connect-use-tempfile=#
  • Scope: Session
  • Dynamic: Yes
  • Data Type: enum
  • Default Value: AUTO
  • Introduced: MariaDB 10.0.15


  • Description: Size of the CONNECT work area used for memory allocation. Permits allocating a larger memory sub-allocation space when dealing with very large if sub-allocation fails. If the specified value is too big and memory allocation fails, the size of the work area remains but the variable value is not modified and should be reset.
  • Commandline: --connect-work-size=#
  • Scope: Global, Session (Session-only from CONNECT 1.03.005)
  • Dynamic: Yes
  • Data Type: numeric
  • Default Value: 67108864
  • Range: 4194304 upwards, depending on the physical memory size
  • Introduced: MariaDB 10.0.11


  • Description: Console trace value. Set to 0 (no trace), or to other values if a console tracing is desired. Note that to test this handler, MariaDB should be executed with the --console parameter because CONNECT prints some error and trace messages on the console. In some Linux versions, this is re-routed into the error log file. Console tracing can be set on the command line or later by names or values. Valid values (from Connect 1.06.006) include:
    • 0: No trace
    • YES or 1: Basic trace
    • MORE or 2: More tracing
    • INDEX or 4: Index construction
    • MEMORY or 8: Allocating and freeing memory
    • SUBALLOC or 16: Sub-allocating in work area
    • QUERY or 32: Constructed query sent to external server
    • STMT or 64: Currently executing statement
    • HANDLER or 128: Creating and dropping CONNECT handlers
    • BLOCK or 256: Creating and dropping CONNECT objects
    • MONGO or 512: Mongo and REST (from Connect 1.06.0010) tracing
  • For example:
    • set global connect_xtrace=0; No trace
    • set global connect_xtrace='YES'; By name
    • set global connect_xtrace=1; By value
    • set global connect_xtrace='QUERY,STMT'; By name
    • set global connect_xtrace=96; By value
    • set global connect_xtrace=1023; Trace all
  • Commandline: --connect-xtrace=#
  • Scope: Global
  • Dynamic: Yes
  • Data Type: set (>= Connect 1.06.006), integer (<= Connect 1.06.005)
  • Default Value: 0
  • Valid Values: See description (>= Connect 1.06.006)
  • Range: 0 to 2147483647 (<= Connect 1.06.005)

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