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.

Design limitations

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.

Database size

Limitation: The default maximum database size is 100GiB. This size can be modified using the options --max-index-size & --max-task-db-size as described in the configuration reference.

Explanation: MeiliSearch uses two databases: one for storage and one for tasks. On launch, LMDB needs to know the maximum size that it will need to reserve on disk for both of them.

Maximum 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 datatypes.

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 datatypes.

Maximum 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 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 datatype 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.

Other limitations

Payload size

Limitation: The default limit for the payload size is ~100MB.

Explanation: MeiliSearch memory consumption can be an issue in some systems and keeping payload sizes relatively small ensures an optimal experience for most users. This limit can be modified if you want to take full advantage of particularly powerful hardware.