What happens if an index does not fit into ram?
Indexes do not have to fit entirely into RAM in all cases. If the value of the indexed field increments with every insert, and most queries select recently added documents; then MongoDB only needs to keep the parts of the index that hold the most recent or “right-most” values in RAM.
Are DB indexes kept in-memory?
An index is usually maintained as a B+ Tree on disk & in-memory, and any index is stored in blocks on disk. The entries in the index block are always sorted on the index/search key. The leaf index block of the index contains a row locator.
Can indexes slow down queries?
As shown, indexes can speed up some queries and slow down others. In this article, we provided some basic guidelines for clustered and nonclustered indexes, as well as which columns are preferred to build indexes on, and which should be avoided.
What is the maximum size of index key limit and number of indexes per collection?
Explanation. The total size of an index entry, which can include structural overhead depending on the BSON type, must be less than 1024 bytes. A single collection can have no more than 64 indexes.
Does data type matter while creating index?
It does not matter if the data in a column is generally increasing. If you create an index on the column, the index will create it’s own data structure that will simply reference the actual items in your table without concern for stored order (a non-clustered index).
When to use a B + tree structure in InnoDB?
InnoDB uses a B+Tree structure for its indexes. A B+Tree is particularly efficient when data doesn’t fit in memory and must be read from the disk, as it ensures that a fixed maximum number of reads would be required to access any data requested, based only on the depth of the tree, which scales nicely.
How is the index page structure in InnoDB?
The physical structure of InnoDB’s INDEX pages was described in The physical structure of InnoDB index pages. We’ll now look into how InnoDB logically structures its indexes, using some practical examples. InnoDB uses a B+Tree structure for its indexes.
How are InnoDB tables created in MySQL 5.7?
InnoDB In-Memory Structures Buffer Pool Change Buffer Adaptive Hash Index Log Buffer InnoDB On-Disk Structures Tables Creating InnoDB Tables Creating Tables Externally Importing InnoDB Tables Moving or Copying InnoDB Tables
Where does the next record start in InnoDB?
For both leaf and non-leaf pages, each record (including the infimum and supremum system records) contain a “next record” pointer, which stores an offset (within the page) to the next record. The linked list starts at infimum and links all records in ascending order by key, terminating at supremum.