Connection Pool Parameters
When a connection pool is used to access the database, database connections are established and then stored in the memory as objects during system running. When you need to access the database, no new connection is established. Instead, an existing idle connection is selected from the connection pool. After you finish accessing the database, the database does not disable the connection but puts it back into the connection pool. The connection can be used for the next access request.
min_pool_size
Parameter description: Specifies the minimum number of connections between a CN's connection pool and another CN/DN.
Type: POSTMASTER
Value range: an integer ranging from 1 to 65535
Default value: 1
max_pool_size
Parameter description: Specifies the maximum number of connections between a CN's connection pool and another CN/DN.
Type: POSTMASTER
Value range: an integer ranging from 1 to 65535
Default value: 800 for CNs and 5000 for DNs
persistent_datanode_connections
Parameter description: Specifies whether to release the connection for the current session.
Type: USERSET
Value range: Boolean
- off indicates that the connection for the current session will be released.
- on indicates that the connection for the current session will not be released.
After this function is enabled, a session may hold a connection but does not run a query. As a result, other query requests fail to be connected. To fix this problem, the number of sessions must be less than or equal to max_active_statements.
Default value: off
cache_connection
Parameter description: Specifies whether to reclaim the connections of a connection pool.
Type: SIGHUP
Value range: Boolean
- on indicates that the connections of a connection pool will be reclaimed.
- off indicates that the connections of a connection pool will not be reclaimed.
Default value: on
enable_force_reuse_connections
Parameter description: Specifies whether a session forcibly reuses a new connection.
Type: BACKEND
Value range: Boolean
- on indicates that the new connection is forcibly used.
- off indicates that the current connection is used.
Default value: off
This is a session connection parameter. You are advised not to configure this parameter.
enable_pooler_parallel
Parameter description: Specifies whether a CN's connection pool can be connected in parallel mode.
Type: SIGHUP
Value range: Boolean
- on indicates that a CN's connection pool can be connected in parallel mode.
- off indicates that a CN's connection pool cannot be connected in parallel mode.
Default value: on
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