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    PolarDB:Parameters

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    PolarDB:Parameters

    Last Updated:Jul 16, 2026

    This topic describes the IMCI-related parameters and supported data types.

    Configuration parameters

    Parameter

    Valid values

    Default value

    Description

    polar_csi.enable_query

    on|off

    off

    Specifies whether queries are allowed to use the IMCI. Valid values:

    • off (default): Queries are not allowed to use the IMCI.

    • on: Queries are allowed to use the IMCI.

    polar_csi.cost_threshold

    1~1000000000

    50000

    When the query cost is less than this threshold, the query statement does not use the IMCI for acceleration. Adjust the actual value based on your business workload.

    • If the value is too large, time-consuming SQL statements cannot use the IMCI, resulting in slower queries.

    • If the value is too small, simple SQL statements use the IMCI, which reduces system concurrency.

    Note

    • You can use EXPLAIN or EXPLAIN ANALYZE to query and analyze the cost of SQL statements.

    • Oracle syntax compatibility 2.0: In minor engine version 2.0.14.13.28.0 and later, the default value of this parameter is changed to 50000. In earlier versions, the default value was 1000.

    polar_csi.max_parallel_workers

    1~512

    2

    The parallelism of the IMCI, that is, the CPU resources that a single SQL statement can use. In general, a higher degree of parallelism delivers better performance.

    The actual value depends on your cluster resource specifications. Adjust the value based on the cluster specifications. We recommend that you do not set a value greater than the number of CPU cores of the compute node.

    Note

    The polar_csi.max_parallel_workers parameter was previously named polar_csi.exec_parallel in earlier kernel versions. For kernel versions that do not support polar_csi.max_parallel_workers, use polar_csi.exec_parallel instead.

    • Oracle syntax compatibility 2.0:

      • Use polar_csi.exec_parallel in versions 2.0.14.20.42.0 and earlier.

      • Use polar_csi.max_parallel_workers in versions 2.0.14.20.43.0 and later.

    polar_csi.memory_limit

    1~1048576

    4096

    The size of memory that can be used by the IMCI. Unit: MB.

    A larger memory threshold enables faster index creation. Adjust the value based on the cluster specifications. We recommend that you do not set a value greater than 25% of the cluster memory. Otherwise, out-of-memory (OOM) errors may occur.

    Note

    Oracle syntax compatibility 2.0: In minor engine version 2.0.14.19.40.0 and later, the default value of this parameter is changed to 4096. In earlier versions, the default value was 1024.

    polar_csi.flush_count

    2048~20480000

    204800

    The number of rows to be committed in each batch when the index is created.

    Increasing the number of rows can improve the creation efficiency, but it also requires more memory.

    polar_csi.update_interval

    0~3600

    1

    The interval at which real-time performance of row-column data is periodically updated. Unit: seconds.

    Increasing the update interval can merge small transactions of the same type, thereby improving data update efficiency when there is a large number of transactions.

    Note

    Oracle syntax compatibility 2.0: In minor engine version 2.0.14.13.28.0 and later, this parameter is added to improve the real-time performance of the IMCI.

    polar_csi.update_batch_count

    1024~4294967295

    100000

    The threshold for the number of rows to update in a batch.

    The maximum number of rows in a single update transaction. Increasing this threshold improves data update efficiency.

    Note

    Oracle syntax compatibility 2.0: In minor engine version 2.0.14.13.28.0 and later, this parameter is added to improve the real-time performance of the IMCI.

    polar_csi.forward_replay_wait

    on|off

    off

    The consistency level of IMCIIMCI data query. Valid values:

    • off: eventual consistency. The IMCI data may lag behind the rowstore data.

    • on: strong consistency. Queries wait until the columnstore data is replayed to the latest data before execution. When the write pressure is high, enabling this parameter may cause a long waiting time.

    polar_csi.forward_replay_wait_lsn_diff

    0~INT_MAX

    0

    The maximum LSN latency allowed for row-column synchronization. If the latency exceeds the specified threshold, the columnstore engine is no longer used. Unit: BYTE.

    Note

    • This parameter takes effect only when polar_csi.forward_replay_wait is enabled.

    • This parameter is applicable only to the following versions:

      Oracle syntax compatibility 2.0: Minor engine version 2.0.14.19.40.0 and later.

    polar_csi.sync_addcolumn

    on|off

    off

    Specifies whether to synchronize Add Column operations to the IMCI.

    Note

    This parameter is applicable only to the following versions:

    Oracle syntax compatibility 2.0: Minor engine version 2.0.14.19.40.0 and later.

    Data types

    Category

    Data type

    Basic data types

    BOOLEAN, ARRAY, BIT, UUID

    String and binary types

    BPCHAR, CHAR, VARCHAR, TEXT, NAME, BYTEA

    Date and time types

    DATE, TIME, TIMESTAMP, TIMESTAMPTZ, INTERVAL

    Numeric types

    BIGINT, DECIMAL, DOUBLE PRECISION, FLOAT4, FLOAT8, INTEGER, NUMERIC, REAL, SERIAL, SHORT, SMALLINT

    Composite types

    JSON, JSONB, ENUM, BITSTRING, VARCHAR[], TEXT[]

    Note

    Oracle syntax compatibility 2.0: In minor engine version 2.0.14.19.40.0 and later, the data types BITSTRING, VARCHAR[], and TEXT[] are added.