ALTER TABLE SET PARAM

ALTER TABLE SET PARAM sets table parameters via SQL.

note

• Checking table metadata can be done via the tables() and table_columns() functions, as described in the meta functions documentation page.

Syntax

maxUncommittedRows - defines the maximum number of uncommitted rows per-table to keep in memory before triggering a commit for a specific table.

The purpose of specifying maximum uncommitted rows per table is to reduce the occurrences of resource-intensive commits when ingesting out-of-order data.

The global setting for the same parameter is cairo.max.uncommitted.rows.

Example

The values for maximum uncommitted rows can be changed per each table with the following SQL:

Altering out-of-order parameters via SQL

ALTER TABLE my_table SET PARAM maxUncommittedRows = 10000

Checking the values per-table may be done using the tables() function:

List table metadata

SELECT id, name, maxUncommittedRows FROM tables();

id	name	maxUncommittedRows
1	my_table	10000

For more details on retrieving table and column information, see the meta functions documentation.

Parameters for QuestDB 6.5.5 and earlier versions

note

Deprecated content

• For QuestDB 6.5.5 and earlier versions, the following keywords are useful for configuring out-of-order ILP data ingestion on a per-table basis. For more information on more details and when to apply them, see the documentation for out-of-order data commits and ILP commit strategy.

• From QuestDB 6.6 onwards, the database adjusts relevant settings automatically and provides maximum ingestion speed.

Syntax

For context on commit lag, see the guide for configuring commit lag of out-of-order data and ILP commit strategy.

commitLag allows for specifying the expected maximum lag of late-arriving records when ingesting out-of-order data. The purpose of specifying a commit lag per table is to reduce the occurrences of resource-intensive commits when ingesting out-of-order data. Incoming records will be kept in memory until for the duration specified in lag, then all records up to the boundary will be ordered and committed.

commitLag expects a value with a modifier to specify the unit of time for the value:

unit	description
us	microseconds
s	seconds
m	minutes
h	hours
d	days

To specify commitLag value to 20 seconds:

ALTER TABLE my_table SET PARAM commitLag = 20s