MongoDB Index (5)

1 Creating an Index

1 is a positive-order index, and 1 is a negative-order index

Indexing increases query time by pressing, reducing insertion time

Db.books.ensureIndex ({number:1})

2. Create an index, specify a name

Db.book.ensureIndex ({name:-1},{name: "BookName"})

3. Unique index

Db.books.ensureIndex ({name:1},{unique:true})

4. Remove duplicate values

Db.books.ensureIndex ({name:1},{unique:true,dropdups:true})

5. Specifying an index for querying

Db.books.find ({no:1}). Hint ({no:1})

6. What query index is currently used

Db.books.find ({no:1}). Explain ()

7. Index of production look

Db.system.indexes.find ()

8. Creating an index locks the table, allowing the creation of an index to be resolved in the background

Db.books.ensureIndex ({number:1},{background:true})

9. Deleting an index

Db.runcommand ({dropindexes: "Books", Index: "No_1"})

MongoDB Index (5)