Configuration parameters

Redis Query Engine can be tuned through multiple configuration parameters. Some of these parameters can only be set at load-time, while other parameters can be set either at load-time or at run-time.

Redis Query Engine configuration parameters

The following table summarizes which configuration parameters can be set at run-time, and compatibility with Redis Software and Redis Cloud.

search-bg-index-sleep-gap

The number of iterations to run while performing background indexing before usleep(1) (sleep for 1 microsecond) is called, ensuring that Redis can process other commands.

Type: integer

Valid range: [1 .. 4294967295]

Default: 100

search-concurrent-write-mode

If enabled, the tokenization of write queries will be performed concurrently.

Type: boolean

Default: FALSE

search-conn-per-shard

The number of connections to each shard in a cluster. If 0, the number of connections is set to search-workers + 1.

Type: integer

Valid range: [0 .. 9,223,372,036,854,775,807]

Default: 0

search-cursor-max-idle

The maximum idle time (in ms) that can be set to the cursor api.

Type: integer

Valid range: [0 .. 9,223,372,036,854,775,807]

Default: 300000

search-cursor-read-size

Type: integer

Default: 1000

search-cursor-reply-threshold

The maximum number of replies to accumulate before triggering _FT.CURSOR READ on the shards.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Default: 1

search-default-dialect

The default DIALECT to be used by FT.CREATE, FT.AGGREGATE, FT.EXPLAIN, FT.EXPLAINCLI, and FT.SPELLCHECK. See Query dialects for more information.

Default: 1

search-ext-load

If present, Redis will try to load an extension dynamic library from the specified file path. See Extensions for details.

Type: string

Default: not set

search-fork-gc-clean-numeric-empty-nodes

Clean empty nodes from numeric tree.

Type: boolean

Default: TRUE

search-fork-gc-clean-threshold

The fork GC will only start to clean when the number of uncleaned documents exceeds this threshold, otherwise it will skip this run.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Default: 100

search-fork-gc-retry-interval

Interval (in seconds) in which Redis will retry to run fork GC in case of a failure. This setting can only be combined with the search-gc-policy FORK setting.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Default: 5

search-fork-gc-run-interval

Interval (in seconds) between two consecutive fork GC runs. This setting can only be combined with the search-gc-policy FORK setting.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Default: 30

search-fork-gc-sleep-before-exit

The number of seconds for the fork GC to sleep before exit. This value should always be set to 0 except when testing.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Default: 0

search-friso-ini

If present, load the custom Chinese dictionary from the specified path. See Using custom dictionaries for more details.

Type: string

Default: not set

GC_POLICY

The garbage collection policy. The two supported policies are:

• FORK: uses a forked thread for garbage collection (v1.4.1 and above). This is the default GC policy since v1.6.1 and is ideal for general purpose workloads.
• LEGACY: uses a synchronous, in-process fork. This is ideal for read-heavy and append-heavy workloads with very few updates/deletes. Deprecated in v2.6.0.

Note: When GC_POLICY is set to FORK, it can be combined with the search-fork-gc-run-interval and search-fork-gc-retry-interval settings.

Type: string

Valid values: FORK or DEFAULT

Default: FORK

search-gc-scan-size

The bulk size of the internal GC used for cleaning up indexes.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Redis CE default: 100

Redis Software default: -1 (unlimited)

Redis Cloud defaults:

• Flexible & Annual: -1 (unlimited)
• Free & Fixed: 10000

search-index-cursor-limit

Added in v2.10.8.

The maximum number of cursors that can be opened, per shard, at any given time. Cursors can be opened by the user via FT.AGGREGATE WITHCURSOR. Cursors are also opened internally by the Redis Query Engine for long-running queries. Once INDEX_CURSOR_LIMIT is reached, any further attempts to open a cursor will result in an error.

Type: integer

Default: 128

search-max-aggregate-results

The maximum number of results to be returned by the FT.AGGREGATE command if LIMIT is used.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Redis CE default: -1 (unlimited)

Redis Software default: -1 (unlimited)

Redis Cloud defaults:

• Flexible & Annual: -1 (unlimited)
• Free & Fixed: 10000

search-max-doctablesize

The maximum size of the internal hash table used for storing documents. Note: this configuration option doesn't limit the number of documents that can be stored. It only affects the hash table internal array maximum size. Decreasing this property can decrease the memory overhead in cases where the index holds a small number of documents that are constantly updated.

Type: integer

Valid range: [1 .. 18,446,744,073,709,551,615]

Default: 1000000

search-max-expansions

This parameter is an alias for search-max-prefix-expansions.

search-max-prefix-expansions

The maximum number of expansions allowed for query prefixes. The maximum number of expansions allowed for query prefixes. Setting it too high can cause performance issues. If search-max-prefix-expansions is reached, the query will continue with the first acquired results. The configuration is applicable for all affix queries including prefix, suffix, and infix (contains) queries.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Default: 200

search-max-search-results

The maximum number of results to be returned by the FT.SEARCH command if LIMIT is used. Set it to -1 to remove the limit.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Redis CE default: 1000000

Redis Software default: 1000000

Redis Cloud defaults:

• Flexible & Annual: 1000000
• Free & Fixed: 10000

search-min-operation-workers

The number of worker threads to use for background tasks when the server is in an operation event.

Type: integer

Valid range: [0 .. 8192]

Default: 4

search-min-phonetic-term-len

The minimum length of term to be considered for phonetic matching.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Default: 3

search-min-prefix

The minimum number of characters allowed for prefix queries (e.g., hel*). Setting it to 1 can reduce performance.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Default: 2

search-min-stem-len

The minimum word length to stem. Setting it lower than 4 can reduce performance.

Type: integer

Valid range: [2 .. 4,294,967,295]

Redis CE default: 4

Redis Software and Redis Cloud default: 2

search-multi-text-slop

Set the delta that is used to increase positional offsets between array slots for multi text values. This will allow you to control the level of separation between phrases in different array slots; related to the SLOP parameter of FT.SEARCH command.

Type: integer

Valid range: [0 .. 4,294,967,295]

Default: 100

search-no-mem-pools

Set Redis Query Engine to run without memory pools.

Type: boolean

Default: FALSE

search-no-gc

If set to TRUE, garbage collection is disabled for all indexes.

Type: boolean

Default: FALSE

search-on-timeout

The response policy for queries that exceed the search-timeout setting can be one of the following:

• RETURN: this policy will return the top results accumulated by the query until it timed out.
• FAIL: will return an error when the query exceeds the timeout value.

Type: string

Valid values: RETURN, FAIL

Default: RETURN

search-partial-indexed-docs

Added in v2.0.0.

Enable/disable the Redis command filter. The filter optimizes partial updates of hashes and may avoid re-indexing the hash if changed fields are not part of the schema.

The Redis command filter will be executed upon each Redis command. Though the filter is optimized, this will introduce a small increase in latency on all commands.
This configuration is best used with partially indexed documents where the non-indexed fields are updated frequently.

Type: integer

Valid values: 0 (false), 1 (true)

Default: 0

search-raw-docid-encoding

Disable compression for DocID inverted indexes to boost CPU performance.

Type: boolean

Default: FALSE

search-threads

Sets the number of search threads in the coordinator thread pool.

Type: integer

search-tiered-hnsw-buffer-limit

Used for setting the buffer limit threshold for vector tiered HNSW indexes. If Redis is using WORKERS for indexing, and the number of vectors waiting in the buffer to be indexed exceeds this limit, new vectors are inserted directly into HNSW.

Type: integer

Valid range: [0 .. 9,223,372,036,854,775,807]

Default: 1024

search-timeout

The maximum amount of time in milliseconds that a search query is allowed to run. If this time is exceeded, Redis returns the top results accumulated so far, or an error depending on the policy set with search-on-timeout. The timeout can be disabled by setting it to 0.

Type: integer

Value range: [1 .. 9,223,372,036,854,775,807]

Redis CE default: 500

Redis Software default: 500

Redis Cloud defaults:

• Flexible & Annual: 500
• Free & Fixed: 100

search-topology-validation-timeout

Sets the timeout in milliseconds for topology validation. After this timeout, any pending requests will be processed, even if the topology is not fully connected. A value of 0 means no timeout.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Default: 30000

search-union-iterator-heap

The minimum number of iterators in a union at which the iterator will switch to a heap based implementation.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Default: 20

search-upgrade-index

Relevant only when loading an v1.x RDB file. Specify the argument for upgrading the index. This configuration setting is a special configuration option introduced to upgrade indexes from v1.x Redis Query Engine versions, otherwise known as legacy indexes. This configuration option needs to be given for each legacy index, followed by the index name and all valid options for the index description (also referred to as the ON arguments for following hashes) as described on FT.CREATE command page.

Type: string

Default: there is no default for index name, and the other arguments have the same defaults as with the FT.CREATE command.

Example

search-upgrade-index idx PREFIX 1 tt LANGUAGE french LANGUAGE_FIELD MyLang SCORE 0.5 SCORE_FIELD MyScore
    PAYLOAD_FIELD MyPayload UPGRADE_INDEX idx1

search-vss-max-resize

Added in v2.4.8.

The maximum memory resize (in bytes) for vector indexes. The maximum memory resize (in bytes) for vector indexes. This value will override default memory limits if you need to allow for a large BLOCK_SIZE.

Type: integer

Valid range: [0 .. 4,294,967,295]

Default: 0

search-workers-priority-bias-threshold

The number of high priority tasks to be executed at any given time by the worker thread pool before executing low priority tasks. After this number of high priority tasks are being executed, the worker thread pool will execute high and low priority tasks alternately.

Type: integer

Valid range: [1 .. 9,223,372,036,854,775,807]

Default: 1

search-workers

The number of worker threads to use for query processing and background tasks.

Type: integer

Valid range: [0 .. 8192]

Default: 0

Set configuration parameters at module load-time (deprecated)

These methods are deprecated beginning with Redis CE v8.0.0.

Setting configuration parameters at load-time is done by appending arguments after the --loadmodule argument when starting a server from the command line, or after the loadmodule directive in a Redis config file. For example:

In redis.conf:

loadmodule ./redisearch.so [OPT VAL]...

From the Redis CLI, using the MODULE LOAD command:

127.0.0.6379> MODULE LOAD redisearch.so [OPT VAL]...

From the command line:

$ redis-server --loadmodule ./redisearch.so [OPT VAL]...

Set configuration parameters at run-time (for supported parameters, deprecated)

These methods are deprecated beginning with Redis CE v8.0.0.

Redis Query Engine exposes the FT.CONFIG endpoint to allow for the setting and retrieval of configuration parameters at run-time.

To set the value of a configuration parameter at run-time (for supported parameters), simply run:

FT.CONFIG SET OPT1 VAL1

Similarly, you can retrieve current configuration parameter values using:

FT.CONFIG GET OPT1
FT.CONFIG GET *

Values set using FT.CONFIG SET are not persisted after server restart.