---
aliases:
- /develop/interact/search-and-query/administration/configuration
- /develop/interact/search-and-query/basic-constructs/configuration-parameters
categories:
- docs
- develop
- stack
- oss
- rs
- rc
- oss
- kubernetes
- clients
description: 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.
linkTitle: Configuration parameters
title: Configuration parameters
weight: 1
---
{{< note >}}
As of Redis 8 in Redis Open Source (Redis 8), configuration parameters for Redis Query Engine (RQE) are now set in the following ways:
* At load time via your `redis.conf` file.
* At run time (where applicable) using the [`CONFIG SET`]({{< relref "/commands/config-set" >}}) command.
Also, Redis 8 persists RQE configuration parameters just like any other configuration parameters (e.g., using the [`CONFIG REWRITE`]({{< relref "/commands/config-rewrite/" >}}) command).
{{< /note >}}
## RQE configuration parameters
The following table summarizes which configuration parameters can be set at run-time, and compatibility with Redis Software and Redis Cloud.
| Parameter name
(version < 8.0) | Parameter name
(version ≥ 8.0) | Run-time | Redis
Software | Redis
Cloud |
| :------- | :------- | :------- | :------- | :------- |
| BG_INDEX_SLEEP_GAP | [search-bg-index-sleep-gap](#search-bg-index-sleep-gap) | :white_large_square: |||
| CONCURRENT_WRITE_MODE | [search-concurrent-write-mode](#search-concurrent-write-mode) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| CONN_PER_SHARD | [search-conn-per-shard](#search-conn-per-shard) | :white_check_mark: |||
| CURSOR_MAX_IDLE | [search-cursor-max-idle](#search-cursor-max-idle) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| CURSOR_READ_SIZE | [search-cursor-read-size](#search-cursor-read-size) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| CURSOR_REPLY_THRESHOLD | [search-cursor-reply-threshold](#search-cursor-reply-threshold) | :white_check_mark: |||
| DEFAULT_DIALECT | [search-default-dialect](#search-default-dialect) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| EXTLOAD | [search-ext-load](#search-ext-load) | :white_large_square: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| FORK_GC_CLEAN_THRESHOLD | [search-fork-gc-clean-threshold](#search-fork-gc-clean-threshold) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| FORK_GC_RETRY_INTERVAL | [search-fork-gc-retry-interval](#search-fork-gc-retry-interval) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| FORK_GC_RUN_INTERVAL | [search-fork-gc-run-interval](#search-fork-gc-run-interval) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| FORKGC_SLEEP_BEFORE_EXIT | [search-fork-gc-sleep-before-exit](#search-fork-gc-sleep-before-exit) | :white_check_mark: |||
| FRISOINI | [search-friso-ini](#search-friso-ini) | :white_large_square: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| [GC_POLICY](#gc_policy) | There is no matching `CONFIG` parameter. | :white_large_square: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| GCSCANSIZE | [search-gc-scan-size](#search-gc-scan-size) | :white_large_square: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| INDEX_CURSOR_LIMIT | [search-index-cursor-limit](#search-index-cursor-limit) | :white_large_square: |||
| INDEX_THREADS | search-index-threads | :white_large_square: |||
| MAXAGGREGATERESULTS | [search-max-aggregate-results](#search-max-aggregate-results) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| MAXDOCTABLESIZE | [search-max-doctablesize](#search-max-doctablesize) | :white_large_square: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| MAXEXPANSIONS | [search-max-expansions](#search-max-expansions) | :white_check_mark: |||
| MAXPREFIXEXPANSIONS | [search-max-prefix-expansions](#search-max-prefix-expansions) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| MAXSEARCHRESULTS | [search-max-search-results](#search-max-search-results) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| MIN_OPERATION_WORKERS | [search-min-operation-workers](#search-min-operation-workers) | :white_check_mark: |||
| MIN_PHONETIC_TERM_LEN | [search-min-phonetic-term-len](#search-min-phonetic-term-len) | :white_check_mark: |||
| MINPREFIX | [search-min-prefix](#search-min-prefix) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| MINSTEMLEN | [search-min-stem-len](#search-min-stem-len) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| MULTI_TEXT_SLOP | [search-multi-text-slop](#search-multi-text-slop) | :white_large_square: |||
| NO_MEM_POOLS | [search-no-mem-pools](#search-no-mem-pools) | :white_large_square: |||
| NOGC | [search-no-gc](#search-no-gc) | :white_large_square: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| ON_TIMEOUT | [search-on-timeout](#search-on-timeout) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| PARTIAL_INDEXED_DOCS | [search-partial-indexed-docs](#search-partial-indexed-docs) | :white_large_square: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| RAW_DOCID_ENCODING | [search-raw-docid-encoding](#search-raw-docid-encoding) | :white_large_square: |||
| SEARCH_THREADS | [search-threads](#search-threads) | :white_large_square: |||
| SEARCH_IO_THREADS | [search-io-threads](#search-io-threads) | :white_large_square: |||
| TIERED_HNSW_BUFFER_LIMIT | [search-tiered-hnsw-buffer-limit](#search-tiered-hnsw-buffer-limit) | :white_large_square: |||
| TIMEOUT | [search-timeout](#search-timeout) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| TOPOLOGY_VALIDATION_TIMEOUT | [search-topology-validation-timeout](#search-topology-validation-timeout) | :white_check_mark: |||
| UNION_ITERATOR_HEAP | [search-union-iterator-heap](#search-union-iterator-heap) | :white_check_mark: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| UPGRADE_INDEX | [search-upgrade-index](#search-upgrade-index) | :white_large_square: | ✅ Supported
| ✅ Flexible & Annual
❌ Free & Fixed |
| VSS_MAX_RESIZE | [search-vss-max-resize](#search-vss-max-resize) | :white_check_mark: |||
| WORKERS_PRIORITY_BIAS_THRESHOLD | [search-workers-priority-bias-threshold](#search-workers-priority-bias-threshold) | :white_large_square: |||
| WORKERS | [search-workers](#search-workers) | :white_check_mark: |||
| OSS_GLOBAL_PASSWORD | Deprecated in v8.0.0. Replace with the `masterauth` password. | :white_large_square: | ✅ Supported
| ❌ Flexible & Annual
❌ Free & Fixed |
| MT_MODE | Deprecated in v8.0.0. Use search-workers. | :white_large_square: |||
| PRIVILEGED_THREADS_NUM | Deprecated in v8.0.0. Use search-workers-priority-bias-threshold.| :white_large_square: |||
| WORKER_THREADS | Deprecated in v8.0.0. Use search-min-operation-workers. | :white_large_square: |||
| SAFEMODE | Deprecated in v1.6.0. This is now the default setting. | :white_large_square: |||
| FORK_GC_CLEAN_NUMERIC_EMPTY_NODES | Deprecated in v8.0.0. | :white_large_square: |||
{{< note >}}
Parameter names for Redis Open Source versions < 8.0, while deprecated, will still be supported in Redis 8.
{{< /note >}}
---
### 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]({{< relref "/develop/ai/search-and-query/advanced-concepts/aggregations#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]({{< relref "/develop/ai/search-and-query/advanced-concepts/dialects" >}})
to be used by [`FT.CREATE`]({{< relref "/commands/ft.create/" >}}), [`FT.AGGREGATE`]({{< relref "/commands/ft.aggregate/" >}}), [`FT.EXPLAIN`]({{< relref "/commands/ft.explain/" >}}), [`FT.EXPLAINCLI`]({{< relref "/commands/ft.explaincli/" >}}), and [`FT.SPELLCHECK`]({{< relref "/commands/ft.spellcheck/" >}}).
See [Query dialects]({{< relref "/develop/ai/search-and-query/advanced-concepts/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]({{< relref "/develop/ai/search-and-query/administration/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`](#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`](#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]({{< relref "/develop/ai/search-and-query/advanced-concepts/chinese#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 Open Source 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`]({{< relref "/commands/ft.aggregate/" >}}). Cursors are also opened internally by the RQE for long-running queries. Once `INDEX_CURSOR_LIMIT` is reached, any further attempts to open a cursor will result in an error.
{{% alert title="Notes" color="info" %}}
* Caution should be used in modifying this parameter. Every open cursor results in additional memory usage.
* Cursor usage should be regulated first by use of [`FT.CURSOR DEL`]({{< relref "/commands/ft.cursor-del/" >}}) and/or [`MAXIDLE`]({{< relref "/commands/ft.aggregate/" >}}) prior to modifying `INDEX_CURSOR_LIMIT`
* See [Cursor API]({{< relref "/develop/ai/search-and-query/advanced-concepts/aggregations#cursor-api" >}}) for more details.
{{% /alert %}}
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 Open Source 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).
### 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 Open Source 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 (for example, 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 Open Source 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 RQE 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`](#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-io-threads
Sets the number of threads used in the coordinator to run I/O tasks with other shards.
Type: integer
Valid range: `[1 .. 256]`
Default: 1
### 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`](#search-on-timeout). The timeout can be disabled by setting it to `0`.
{{% alert title="Notes" color="info" %}}
* `search-timeout` refers to query time only.
* Parsing the query is not counted towards `search-timeout`.
* If `search-timeout` was not reached during the search, finalizing operations such as loading document content or reducers continue.
{{% /alert %}}
Type: integer
Value range: `[1 .. 9,223,372,036,854,775,807]`
Redis Open Source 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 RQE 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]({{< relref "/commands/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`]({{< relref "/commands/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
```
{{% alert title="Notes" color="info" %}}
* If the RDB file does not contain a legacy index that's specified in the configuration, a warning message will be added to the log file, and loading will continue.
* If the RDB file contains a legacy index that wasn't specified in the configuration, loading will fail and the server won't start.
{{% /alert %}}
### 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`]({{< relref "/develop/ai/search-and-query/vectors/#creation-attributes-per-algorithm" >}}).
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`
### search-on-oom
Specifies the response policy for queries when the server's current memory usage exceeds the configured [maxmemory](https://redis.io/docs/latest/develop/reference/eviction/#maxmem) limit.
* `IGNORE`: Execute the query regardless of current memory usage.
* `RETURN`: In cluster mode, the query returns partial results from shards that did not exceed the memory limit. Shards that exceed the limit will not contribute results.
* `FAIL`: Will return an error if memory usage exceeds the memory limit.
Type: string
Valid values: `IGNORE`, `RETURN`, `FAIL`
Default: `IGNORE`
{{% alert title="Notes" color="info" %}}
To prevent potential out-of-memory conditions, it is recommended that you set this parameter to FAIL or RETURN rather than IGNORE.
{{% /alert %}}
## Set configuration parameters at module load-time (deprecated)
These methods are deprecated beginning with Redis 8.
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]({{< relref "/operate/oss_and_stack/management/config" >}}):
```
loadmodule ./redisearch.so [OPT VAL]...
```
From the [Redis CLI]({{< relref "/develop/tools/cli" >}}), using the [MODULE LOAD]({{< relref "/commands/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 8.
RQE 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:
```sh
FT.CONFIG SET OPT1 VAL1
```
Similarly, you can retrieve current configuration parameter values using:
```sh
FT.CONFIG GET OPT1
FT.CONFIG GET *
```
Values set using [`FT.CONFIG SET`]({{< relref "/commands/ft.config-set/" >}}) are not persisted after server restart.