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Set Query Options

  • Capella Columnar
  • how-to
    +
    You can use the query options to change the query timeout period, define request-level parameters, and so on.

    Prerequisites

    To use the workbench for Capella Columnar:

    Available Query Options

    When you select query options, you can define the following settings and request-level parameters:

    • Query Timeout

    • Scan Consistency

    • Positional Parameters

    • Named Parameters

    Descriptions of these settings follow.

    Query Timeout Setting

    You define a query timeout to specify the maximum time, in seconds, for the system to spend on a query before timing out.

    This setting accepts a value from 1 to 1800, with a default of 1800.

    Scan Consistency Setting

    The scan consistency setting specifies the consistency guarantee for index scanning. You can select one of the following options:

    • not_bounded: The index scan does not use a timestamp vector. This is the fastest mode, because it avoids the costs of obtaining the vector and waiting for the index to catch up to the vector.

    • request_plus: This option implements bounded consistency. The request includes a scan_vector parameter and value, which is used as a lower bound. You can use this setting to implement read-your-own-writes (RYOW).

    Positional Parameters

    Positional parameters use numeric identifiers to represent values to supply in a query. Capella Columnar automatically supplies numbered identifiers for these parameters as you add them: $1, $2, and so on. The value you enter must use JSON formatting, such as enclosing strings in quotation marks.

    To add positional parameters, click the + button. To remove parameters from last to first, click the - button.

    Example

    You define the following positional parameters:

    $1 "Paris"
$2 "Gare du Nord"

    When you run the following query:

    SELECT * FROM travel-sample.inventory.airport
WHERE airportname <> $2 AND city = $1;

    The result returns the eight documents that have "Paris" as the city but that do not have "Gare du Nord" as the airportname.

    You can then reuse these parameters in other queries as is, change their values, or delete them.

    Named Parameters

    Named parameters store an identifying variable name in addition to the value. The name must start with $, and the value must use JSON formatting, such as enclosing strings in quotation marks.

    To add named parameters, click the + button. To remove parameters from last to first, click the - button.

    Example

    You define a parameter, $n, and specify a value of "Orbit Airlines" for it.

    When you run the following query:

    SELECT * FROM travel-sample.inventory.airport
WHERE name = $n;

    The result returns the single document that has an airline name of "Orbit Airlines".

    You can then reuse $n in other queries as is, change its value, update its name, or delete it.

    See Also