Configure Queries

Capella Operational

You can configure the Query service using request-level query parameters.

Request-Level Parameters

To set a request-level parameter, do one of the following:

Use the Query Options window in the Query tab.
Use the cbq shell at the command line.
Use an SDK client program.

Generally, use the cbq shell or the Query tab as a sandbox to test queries in your Capella cluster. Use an SDK client program for your production queries.

Capella UI
Command Line

To set request-level preferences in the Query tab:

Go to Data Tools Query and click Query Options to display the Query Options window.
Specify the preferences — if a preference is not explicitly listed, click + next to Named Parameters and add its name and value.
Click Save.

For more examples, see the Couchbase Transactions guide.

To set request-level parameters in cbq, use the \SET command. The parameter name must be prefixed by a hyphen.

The following example sets the request-level timeout, pretty-print, and max parallelism parameters, and runs a query:

\SET -timeout "30m";
\SET -pretty true;
\SET -max_parallelism 3;
SELECT * FROM "world" AS hello;

For more examples, see Parameter Manipulation in the cbq documentation.

The table below contains details of all request-level parameters, along with examples.

Table 1. Request-Level Parameters
Name	Description	Schema
args optional	Supplies the values for positional parameters in the statement. Applicable if the statement or prepared statement contains 1 or more positional parameters. The value is an array of JSON values, one for each positional parameter in the statement. Refer to Named Parameters and Positional Parameters for details. Example : `[ "LAX", 6 ]`	< object > array
atrcollection optional	Specifies the collection where the active transaction record (ATR) is stored. The collection must be present. If not specified, the ATR is stored in the default collection in the default scope in the bucket containing the first mutated document within the transaction. The value must be a string in the form `"bucket.scope.collection"` or `"namespace:bucket.scope.collection"`. If any part of the path contains a special character, that part of the path must be delimited in backticks ``. Example : "default:`travel-sample`.transaction.test"	string
auto_execute optional	Specifies that prepared statements should be executed automatically as soon as they are created. This saves you from having to make two separate requests in cases where you want to prepare a statement and execute it immediately. Refer to Auto-Execute for more information. Default : `false` Example : `true`	boolean
client_context_id optional	A piece of data supplied by the client that is echoed in the response, if present. SQL++ is agnostic about the content of this parameter; it is just echoed in the response. Maximum allowed size is 64 characters; all others will be cut. If it contains an escape character `/` or quote `"`, it will be rejected as error code 1110.	string
compression optional	Compression format to use for response data on the wire. Values are case-insensitive. Default : `"NONE"` Example : `"zip"`	enum (ZIP, RLE, LZMA, LZO, NONE)
controls optional	Specifies if there should be a controls section returned with the request results. When set to `true`, the query response document includes a controls section with runtime information provided along with the request, such as positional and named parameters or settings. If the request qualifies for caching, these values will also be cached in the `completed_requests` system keyspace. Example : `true`	boolean
durability_level optional	The level of durability for mutations produced by the request. If the request contains a `BEGIN TRANSACTION` statement, or a DML statement with the tximplicit parameter set to `true`, the durability level is specified for all mutations within that transaction. Durability is also supported for non-transactional DML statements. In this case, the `kvtimeout` parameter is used as the durability timeout. If not specified, the default durability level is `"majority"`. Set the durability level to `"none"` or `""` to specify no durability. Default : `"majority"` Example : `"none"`	enum ("", none, majority, majorityAndPersistActive, persistToMajority)
encoded_plan optional	In databases running Couchbase Server 6.5 and later, this parameter is ignored and has no effect. It is included for compatibility with previous versions of Couchbase Server.	string
encoding optional	Desired character encoding for the query results. Only possible value is `UTF-8` and is case-insensitive. Default : `"UTF-8"`	string
format optional	Desired format for the query results. Values are case-insensitive. Default : `"JSON"` Example : `"XML"`	enum (JSON, XML, CSV, TSV)
kvtimeout optional	The approximate time to wait for a KV get operation before timing out. This applies to statements within a transaction, and to non-transactional statements, whether `durability_level` is set or not. If `use_replica` is enabled for a query, then this parameter also specifies the approximate time to wait before fetching data from a replica vBucket when the active vBucket is inaccessible. The value for this parameter is a string. Its format includes an amount and a mandatory unit, e.g. `10ms` (10 milliseconds) or `0.5s` (half a second). Valid units are: `ns` (nanoseconds) `us` (microseconds) `ms` (milliseconds) `s` (seconds) `m` (minutes) `h` (hours) Specify a duration of `0` or a negative duration to disable. When disabled, no timeout is applied and the KV operation runs for however long it takes. Default : `"2.5s"` Example : `"10ms"`	string
max_parallelism optional	Specifies the maximum parallelism for the query. The default value is the same as the number of partitions of the index selected for the query. Example : `3`	integer (int32)
memory_quota optional	Specifies the maximum amount of memory the request may use, in MB. Specify `0` (the default value) to disable. When disabled, there is no quota. This parameter enforces a ceiling on the memory used for the tracked documents required for processing a request. It does not take into account any other memory that might be used to process a request, such as the stack, the operators, or some intermediate values. Within a transaction, this setting enforces the memory quota for the transaction by tracking the delta table and the transaction log (approximately). Default : `0` Example : `4`	integer (int32)
metrics optional	Specifies that metrics should be returned with query results. Default : `true` Example : `false`	boolean
namespace optional	Specifies the namespace to use. Currently, only the `default` namespace is available. Example : `"default"`	string
numatrs optional	Specifies the total number of active transaction records. Must be a positive integer. Default : `1024` Example : `512`	integer (int32)
pipeline_batch optional	Controls the number of items execution operators can batch for Fetch from the KV. Example : `64`	integer (int32)
pipeline_cap optional	Maximum number of items each execution operator can buffer between various operators. Example : `1024`	integer (int32)
prepared optional	Required if `statement` not provided. The name of the prepared SQL++ statement to be executed. Refer to EXECUTE for examples. If both `prepared` and `statement` are present and non-empty, an error is returned. Example : `"[127.0.0.1:8091]pricy_hotel"`	string
preserve_expiry optional	Specifies whether documents should keep their current expiration setting when modified by a DML statement. If `true`, documents will keep any existing expiration setting when modified by a DML statement. If the DML statement explicitly specifies the document expiration, the statement overrides this parameter, and the expiration is changed. If `false`, document expiration is set to 0 when modified by a DML statement, unless the DML statement explicitly specifies the document expiration. Not supported for statements in a transaction. Default : `false` Example : `true`	boolean
pretty optional	Specifies the query results returned in pretty format. Example : `false`	boolean
profile optional	Specifies if there should be a profile section returned with the request results. The valid values are: `off` — No profiling information is added to the query response. `phases` — The query response includes a profile section with stats and details about various phases of the query plan and execution. Three phase times will be included in the `system:active_requests` and `system:completed_requests` monitoring keyspaces. `timings` — Besides the phase times, the profile section of the query response document will include a full query plan with timing and information about the number of processed documents at each phase. This information will be included in the `system:active_requests` and `system:completed_requests` keyspaces. If `profile` is not set as one of the above values, then the profile setting does not change. Example : `"phases"`	enum (off, phases, timings)
query_context optional	Specifies the namespace, bucket, and scope used to resolve partial keyspace references within the request. The query context may be a full path, containing namespace, bucket, and scope; or a relative path, containing just the bucket and scope. Currently, only the `default` namespace is available. If the namespace name is omitted, the default namespace in the current session is used. Default : `"default:"` Example : `"default:travel-sample.inventory"`	string
readonly optional	Controls whether a query can change a resulting recordset. If `readonly` is `true`, then the following statements are not allowed: CREATE INDEX DROP INDEX INSERT MERGE UPDATE UPSERT When using GET requests, it’s best to set `readonly` to `true`. Default : `false` Example : `true`	boolean
scan_cap optional	Maximum buffered channel size between the indexer client and the query service for index scans. This parameter controls when to use scan backfill. Use `0` or a negative number to disable. Smaller values reduce GC, while larger values reduce indexer backfill. Example : `1024`	integer (int32)
scan_consistency optional	Specifies the consistency guarantee or constraint for index scanning. The valid values are: `not_bounded` — No timestamp vector is used in the index scan. 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. `at_plus` — This implements bounded consistency. The request includes a `scan_vector` parameter and value, which is used as a lower bound. This can be used to implement read-your-own-writes (RYOW). `request_plus` — This implements strong consistency per request. Before processing the request, a current vector is obtained. The vector is used as a lower bound for the statements in the request. If there are DML statements in the request, RYOW is also applied within the request. (If `request_plus` is specified in a query that runs during a failover of an index node, the query waits until the rebalance operation completes and the index data has rebalanced before returning a result.) `statement_plus` — This implements strong consistency per statement. Before processing each statement, a current vector is obtained and used as a lower bound for that statement. Values are case-insensitive. For multi-statement requests, the default behavior is RYOW within each request. If you want to disable RYOW within a request, add a separate `request_consistency` parameter that can be set to `not_bounded`. If the request contains a `BEGIN TRANSACTION` statement, or a DML statement with the tximplicit parameter set to `true`, then this parameter sets the transactional scan consistency. Refer to Transactional Scan Consistency for details. Default : `"not_bounded"` Example : `"at_plus"`	enum (not_bounded, at_plus, request_plus, statement_plus)
scan_vector optional	Required if `scan_consistency` is `at_plus` and `scan_vectors` not provided. Specify the lower bound vector timestamp for one keyspace when using `at_plus` scan consistency. Scan vectors are built of two-element [`value`, `guard`] entries: `value`: a vBucket’s sequence number (a JSON number) `guard`: a vBucket’s UUID (a string) Scan vectors have two forms: Full: an array of [`value`, `guard`] entries, giving an entry for every vBucket in the system. Sparse: an object providing entries for specific vBuckets, mapping a vBucket number (a string) to each [`value`, `guard`] entry. Note that `scan_vector` can only be used if the query uses at most one keyspace; if it is used for a query referencing more than one keyspace, the query will fail with an error. For queries referencing multiple keyspaces, use `scan_vectors`. Example : `{ "5" : [ 5409393, "VB5ID" ], "19" : [ 47574574, "VB19ID" ] }`	object
scan_vectors optional	Required if `scan_consistency` is `at_plus` and `scan_vector` not provided. A map from keyspace names to scan vectors. See `scan_vector`. The scan vectors can be Full or Sparse.	object
scan_wait optional	Can be supplied with `scan_consistency` values of `request_plus`, `statement_plus` and `at_plus`. Specifies the maximum time the client is willing to wait for an index to catch up to the vector timestamp in the request. Specifies how much time the client is willing to wait for the indexer to satisfy the required `scan_consistency` and `scan_vector` criteria. After receiving the scan request, if the indexer is unable to catch up within the `scan_wait` time and initiate the scan, the indexer aborts with an error and the scan fails. Its format includes an amount and a mandatory unit, e.g. `10ms` (10 milliseconds) or `0.5s` (half a second). Valid units are: `ns` (nanoseconds) `us` (microseconds) `ms` (milliseconds) `s` (seconds) `m` (minutes) `h` (hours) Specify `0` or a negative integer to disable. Default : `""` Example : `"30m"`	string (duration)
signature optional	Include a header for the results schema in the response. Default : `true` Example : `false`	boolean
sort_projection optional	If `true`, causes statement projection terms to be sorted alphabetically. If `false` (the default), statement projection terms are returned in the order specified by the query. Default : `false` Example : `true`	boolean
statement optional	Required if `prepared` not provided. Any valid SQL statement for a POST request, or a read-only SQL statement (SELECT, EXPLAIN) for a GET request. If both `prepared` and `statement` are present and non-empty, an error is returned. When specifying the request parameters as form data, the statement may not contain an unescaped semicolon (`;`). If it does, the Query Service responds with error 1040. To avoid this, either URL-encode the semicolon as `%3B`, or just omit the semicolon if possible. This restriction does not apply when specifying the request parameters in JSON format. Example : "SELECT * FROM `travel-sample`.inventory.hotel LIMIT 1"	string
timeout optional	Maximum time to spend on the request before timing out. The value for this parameter is a string. Its format includes an amount and a mandatory unit, e.g. `10ms` (10 milliseconds) or `0.5s` (half a second). Valid units are: `ns` (nanoseconds) `us` (microseconds) `ms` (milliseconds) `s` (seconds) `m` (minutes) `h` (hours) Specify a duration of `0` or a negative duration to disable. When disabled, no timeout is applied and the request runs for however long it takes. If tximplicit or txid is set, this parameter is ignored. The request inherits the remaining time of the transaction as timeout. Example : `"30m"`	string (duration)
txdata optional	Transaction data. For internal use only.	object
txid optional	Required for statements within a transaction. Transaction ID. Specifies the transaction to which a statement belongs. For use with DML statements within a transaction, rollbacks, and commits. The transaction ID should be the same as the transaction ID generated by the `BEGIN TRANSACTION` statement. The transaction must be active and non-expired. Example : `"d81d9b4a-b758-4f98-b007-87ba262d3a51"`	string (UUID)
tximplicit optional	Specifies that a DML statement is a singleton transaction. When this parameter is true, the Query service starts a transaction and executes the statement. If execution is successful, the Query service commits the transaction; otherwise the transaction is rolled back. The statement may not be part of an ongoing transaction. If the txid request-level parameter is set, the `tximplicit` parameter is ignored. Default : `false` Example : `true`	boolean
txstmtnum optional	Transaction statement number. The transaction statement number must be a positive integer, and must be higher than any previous transaction statement numbers in the transaction. If the transaction statement number is lower than the transaction statement number for any previous statement, an error is generated. Example : `10`	integer (int32)
txtimeout optional	Maximum time to spend on a transaction before timing out. Only applies to `BEGIN TRANSACTION` statements, or DML statements for which tximplicit is set. For other statements, it is ignored. Within a transaction, the request-level timeout parameter is ignored. The transaction timeout clock starts when the `BEGIN WORK` statement is successful. Once the transaction timeout is reached, no statement is allowed to continue in the transaction. The value for this parameter is a string. Its format includes an amount and a mandatory unit, e.g. `10ms` (10 milliseconds) or `0.5s` (half a second). Valid units are: `ns` (nanoseconds) `us` (microseconds) `ms` (milliseconds) `s` (seconds) `m` (minutes) `h` (hours) Specify a duration of `0` to disable. When disabled, the request-level timeout is set to the default. The default is `"15s"` for cbq files or scripts, `"2m"` for interactive cbq sessions or redirected input. Example : `"30m"`	string (duration)
use_cbo optional	Specifies whether the cost-based optimizer is enabled. Example : `true`	boolean
use_fts optional	Specifies that the query should use a full-text index. If the query contains a `USING FTS` hint, that takes priority over this parameter. If the query does not contain a `USING FTS` hint, and this parameter is set to true, all full-text indexes are considered for the query. If a qualified full-text index is available, it is selected for the query. If none of the available full-text indexes are qualified, the available GSI indexes are considered instead. Refer to Flex Indexes for more information. Default : `false` Example : `true`	boolean
use_replica optional	Specifies whether a query can fetch data from a replica vBucket if active vBuckets are inaccessible. The possible values are: `off` — read from replica is disabled for this request. `on` — read from replica is enabled for this request, unless it has been disabled for all requests at node level. `unset` — read from replica is specified by the node-level setting. If the node-level setting is also `unset`, read from replica is disabled for this request. Do not enable read from replica when you require consistent results. Only SELECT queries that are not within a transaction can read from replica. Reading from replica is only possible with databases running Couchbase Server 7.6.0 or later. Note that KV range scans cannot currently be started on a replica vBucket. If a query uses sequential scan and a data node becomes unavailable, the query might return an error, even if read from replica is enabled for the request. Default : `"unset"` Example : `"true"`	enum (off, on, unset)
<symbol><identifier> optional	Supplies the value for a named parameter in the statement. Applicable if the statement or prepared statement contains 1 or more named parameters. The name of this property consists of two parts: The `$` character. In databases running Couchbase Server 7.6.0 and later, this may be the `$` character or the `@` character. An identifier that specifies the name of the parameter. This must start with an alpha character, followed by one or more alphanumeric characters. The value of the named parameter can be any JSON value. Refer to Named Parameters and Positional Parameters for details.	string (any JSON value)

Transactional Scan Consistency

If the request contains a BEGIN TRANSACTION statement, or a DML statement with the tximplicit parameter set to true, then the scan_consistency parameter sets the transactional scan consistency. If you specify a transactional scan consistency of request_plus, statement_plus, or at_plus, or if you specify no transactional scan consistency, the transactional scan consistency is set to request_plus; otherwise, the transactional scan consistency is set as specified.

Table 2. Transactional scan consistency
Scan consistency at start of transaction	Transactional scan consistency
Not set	`request_plus`
`not_bounded`	`not_bounded`
`request_plus` `statement_plus` `at_plus`	`request_plus`

Any DML statements within the transaction that have no scan consistency set will inherit from the transactional scan consistency. Individual DML statements within the transaction may override the transactional scan consistency. If you specify a scan consistency of not_bounded for a statement within the transaction, the scan consistency for the statement is set as specified. When you specify a scan consistency of request_plus, statement_plus, or at_plus for a statement within the transaction, the scan consistency for the statement is set to request_plus.

However, request_plus consistency is not supported for statements using a full-text index. If any statement within the transaction uses a full-text index, by means of the SEARCH function or the Flex Index feature, the scan consistency is set to not_bounded for the duration of the full-text search.

Table 3. Overriding the transactional scan consistency
Scan consistency for statement within transaction	Inherited scan consistency
Not set	Transactional scan consistency (`not_bounded` for full-text search)
`not_bounded`	`not_bounded`
`request_plus` `statement_plus` `at_plus`	`request_plus` (`not_bounded` for full-text search)

Named Parameters and Positional Parameters

You can add placeholder parameters to a statement, so that you can safely supply variable values when you run the statement. A placeholder parameter may be a named parameter or a positional parameter.

To add a named parameter to a query, enter a dollar sign $ or an at sign @ followed by the parameter name.
To add a positional parameter to a query, enter a dollar sign $ or an at sign @ followed by the number of the parameter, or enter a question mark ?.

To run a query containing placeholder parameters, you must supply values for the parameters.

You can use an additional request-level parameter to supply the value for a named parameter. The name of this property is a dollar sign $ or an at sign @ followed by the parameter name.
The args request-level parameter enables you to supply a list of values for positional parameters.

You can supply the values for placeholder parameters using any of the methods used to specify request-level parameters.

Couchbase Server 7.6

The at sign @ syntax is only supported in clusters running Couchbase Server 7.6.0 or later. The dollar sign $ syntax is supported in all versions of Couchbase Server.

Examples

To try the examples in this section, set the query context to the inventory scope in the travel sample dataset. For more information, see Query Context.

Example 1. Named Parameters

Capella UI
Command Line

The following query uses named parameter placeholders. The parameter values are supplied using the Query Options window.

Named Parameters
name	`$country`	value	`"France"`
name	`$altitude`	value	`500`

SELECT COUNT(*) FROM airport
WHERE country = $country AND geo.alt > @altitude;

The named parameters and named parameter placeholders in this example use a mixture of @ and $ symbol prefixes. In clusters running Couchbase Server 7.6.0 and later, you can use either of these symbols as preferred. In previous versions of Couchbase Server, you must use the $ symbol prefix.

The following query uses named parameter placeholders. The parameter values are supplied using the cbq shell.

\SET -@country "France";
\SET -$altitude 500;

SELECT COUNT(*) FROM airport
WHERE country = $country AND geo.alt > @altitude;

Example 2. Numbered Positional Parameters

Capella UI
Command Line

The following query uses numbered positional parameter placeholders. The parameter values are supplied using the Query Options window.

Positional Parameters
$1	`"France"`
$2	`500`

SELECT COUNT(*) FROM airport
WHERE country = $1 AND geo.alt > @2;

In this case, the first positional parameter value is used for the placeholder numbered $1, the second positional parameter value is used for the placeholder numbered @2, and so on.

The numbered positional parameter placeholders in this example use a mixture of @ and $ symbol prefixes. In clusters running Couchbase Server 7.6.0 and later, you can use either of these symbols as preferred. In previous versions of Couchbase Server, you must use the $ symbol prefix.

The following query uses numbered positional parameter placeholders. The parameter values are supplied using the cbq shell.

\SET -args ["France", 500];

SELECT COUNT(*) FROM airport
WHERE country = $1 AND geo.alt > @2;

In this case, the first positional parameter value is used for the placeholder numbered $1, the second positional parameter value is used for the placeholder numbered @2, and so on.

Example 3. Unnumbered Positional Parameters

Capella UI
Command Line

The following query uses unnumbered positional parameter placeholders. The parameter values are supplied using the Query Options window.

Positional Parameters
$1	`"France"`
$2	`500`

SELECT COUNT(*) FROM airport
WHERE country = ? AND geo.alt > ?;

In this case, the first positional parameter value is used for the first ? placeholder, the second positional parameter value is used for the second ? placeholder, and so on.

The following query uses unnumbered positional parameter placeholders. The parameter values are supplied using the cbq shell.

\SET -args ["France", 500];

SELECT COUNT(*) FROM airport
WHERE country = ? AND geo.alt > ?;

In this case, the first positional parameter value is used for the first ? placeholder, the second positional parameter value is used for the second ? placeholder, and so on.

For more details and examples, including examples using SDKs, see the Prepare Statements for Reuse guide.