What are the types and characteristics of mysql indexes?
MySQL index types include: 1. B-Tree index: fast equal value, range and prefix search; 2. Hash index: fast equal value search; 3. Full-text index: fuzzy search text field; 4. Spatial index: geospatial query; 5. Covering index: includes all columns required for query, improving query speed; 6. Unique index: ensuring unique index column values, improving data integrity.
MySQL index types and their characteristics
Indices are the key technology for MySQL query optimization and help speed up data Retrieve. MySQL supports multiple index types, each with its own unique characteristics.
1. B-Tree index
This is the most common index type in MySQL. B-Tree is a balanced search tree with data stored in leaf nodes. B-Tree indexes have the following features:
- Supports fast queries for equivalent values, ranges, and prefix searches.
- The index structure is highly balanced and insertion and deletion operations are efficient.
2. Hash index
Hash index stores key-value pairs through a hash table. Data is stored in hash buckets, and the bucket is located directly by the hash value of the key. Hash indexes have the following characteristics:
- are very fast for equivalent searches.
- Cannot be used for sorting and range queries.
- Hash collisions can cause performance degradation.
3. Full-text index
Full-text index is used to search text data. It breaks text into words or phrases and creates an index for each word. Full-text indexing has the following features:
- Supports fast fuzzy search on text fields.
- The index size may be large.
- May have a negative impact on performance.
4. Spatial index
Spatial index is used to search geospatial data. It divides the data space into smaller regions through a hierarchical grid and creates an index for each region. Spatial indexes have the following characteristics:
- Very fast for geospatial queries (such as intersect, contain, etc.).
- Applies only to spatial data types (such as POINT and GEOGRAPHY).
5. Covering index
A covering index is an index that contains all columns required by the query. When the query only involves columns in the index, there is no need to access the data table, thus improving query speed. Covering indexes have the following characteristics:
- are very effective for read-intensive queries.
- Excessive covering index may cause performance degradation.
6. Unique index
Unique index ensures that all values in the indexed column are unique. It has the following characteristics:
- Prevents the insertion of duplicate data.
- Improve data integrity.
- Insertion performance may be reduced in some cases.
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