Meilisearch Documentation v1.0

# Known limitations

Currently, Meilisearch has a number of known limitations. Some of these limitations are the result of intentional design trade-offs, while others can be attributed to LMDB, the key-value store that Meilisearch uses under the hood.

This guide covers hard limits that cannot be altered. Meilisearch also has some default limits that can be changed, such as a default payload limit of 100MB and a default search limit of 20 hits.

# Maximum number of query words

Limitation: The maximum number of terms taken into account for each search query is 10. If a search query includes more than 10 words, all words after the 10th will be ignored.

Explanation: Queries with many search terms can lead to long response times. This goes against our goal of providing a fast search-as-you-type experience.

# Maximum number of document fields

Limitation: Documents have a soft maximum of 1000 fields.

Explanation: There is no limit on how many fields a document can have. However, documents with more than 1000 fields may cause the ranking rules to stop working, leading to undefined behavior.

# Maximum number of words per attribute

Limitation: Meilisearch can index a maximum of 65535 positions per attribute. Any words exceeding the 65535 position limit will be silently ignored.

Explanation: This limit is enforced for relevancy reasons. The more words there are in a given attribute, the less relevant the search queries will be.

# Example

Suppose you have three similar queries: Hello World, Hello, World, and Hello - World. Due to how our tokenizer works, each one of them will be processed differently and take up a different number of "positions" in our internal database.

If your query is Hello World:

  • Hello takes the position 0 of the attribute
  • World takes the position 1 of the attribute

If your query is Hello, World:

  • Hello takes the position 0 of the attribute
  • , takes the position 8 of the attribute
  • World takes the position 9 of the attribute

NOTE

, takes 8 positions as it is a hard separator. You can read more about word separators in our article about data types.

If your query is Hello - World:

  • Hello takes the position 0 of the attribute
  • - takes the position 1 of the attribute
  • World takes the position 2 of the attribute

NOTE

- takes 1 position as it is a soft separator. You can read more about word separators in our article about data types.

# Maximum number of attributes per document

Limitation: Meilisearch can index a maximum of 65,536 attributes per document. If a document contains more than 65,536 attributes, an error will be thrown.

Explanation: This limit is enforced for performance and storage reasons. Overly large internal data structures—resulting from documents with too many fields—lead to overly large databases on disk, and slower search performance.

# Maximum number of concurrent requests

Limitation: Meilisearch can receive a maximum of 1024 API requests at the exact same time. Requests exceeding this limit will cause Meilisearch to thrown an internal error.

Explanation: This limit applies only to receiving requests, not to processing or adding them to the Tasks queue. It is set by LMDB, Meilisearch's storage engine.

# Maximum number of documents in an index

Limitation: An index can contain no more than 4,294,967,296 documents.

Explanation: This is the largest possible value for a 32-bit unsigned integer. Since Meilisearch's engine uses unsigned integers to identify documents internally, this is the maximum number of documents that can be stored in an index.

# Length of individual filterableAttributes values

Limitation: Individual filterableAttributes values are limited to 500 bytes.

Explanation: Meilisearch stores filterableAttributes values as keys in LMDB, a data type whose size is limited to approximately 500 bytes. Note that this only applies to individual values—for example, a genres attribute can contain any number of values such as horror, comedy, or cyberpunk as long as each one of them is smaller than 500 bytes.

# Maximum filter depth

Limitation: Meilisearch does not accept searches with more than 2000 OR filters.

Explanation: OR filters create nested structures which can lead to a stack overflow.

# Example

Either of these filter expressions would cause a search query to fail:

user = 1 OR user = 2 […] OR user = 1500 OR user = 1501 […] OR user = 2000 OR user = 2001

[
  ["user = 1", "user = 2", […], "user = 1500", "user = 1501", […], "user = 2000", "user = 2001"]
]

# Size of integer fields

Limitation: Meilisearch can only exactly represent integers between -2⁵³ and 2⁵³.

Explanation: Meilisearch stores numeric values as double-precision floating-point numbers. This allows for greater precision and increases the range of magnitudes that Meilisearch can represent, but leads to inaccuracies in values beyond certain thresholds (opens new window).

Limitation: By default, Meilisearch returns up to 1000 documents per search.

Explanation: Meilisearch limits the maximum amount of returned search results to protect your database from malicious scraping. You may change this by using the maxTotalHits property of the pagination index settings. maxTotalHits only applies to the search route and has no effect on the get documents endpoint.

# Large datasets and internal errors

Limitation: Meilisearch might throw an internal error when indexing large batches of documents.

Explanation: Indexing a large batch of documents, such as a JSON file over 3.5GB in size, can result in Meilisearch opening too many file descriptors. Depending on your machine, this might reach your system's default resource usage limits and trigger an internal error. Use ulimit (opens new window) or a similar tool to increase resource consumption limits before running Meilisearch. For example, call ulimit -Sn 3000 in a UNIX environment to raise the number of allowed open file descriptors to 3000.

# Maximum database size

Limitation: The maximum size of an index is 500GiB, and the maximum size of the task database is 10GiB.

Explanation: Meilisearch allocates all the virtual memory it requires upfront. The maximum database size ensures instances can contain several large indexes without reaching operating system limits on the amount of virtual memory available to a single process.

# Maximum number of indexes in an instance

Limitation: A single Meilisearch instance can safely contain around 180 indexes in Linux and macOS environments, and around 15 indexes in Windows environments.

Explanation: Operating systems restrict the amount of virtual memory available to a single process. Since Meilisearch allocates the maximum index size for each index upfront, this effectively creates a limit on how many indexes an instance can contain. The values provided are indicative: because of the particularities of each specific setup, the actual maximum number of indexes per instance will vary from machine to machine. A Linux install might contain 200 indexes without issue, or return allocation failures at 181 indexes depending on the runtime environment.

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