mirror of https://gitee.com/bigwinds/arangodb
25 lines
913 B
Plaintext
25 lines
913 B
Plaintext
!CHAPTER Hash Indexes
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!SUBSECTION Introduction to Hash Indexes
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This is an introduction to ArangoDB's hash indexes.
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It is possible to define a hash index on one or more attributes (or paths) of a
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document. This hash index is then used in queries to locate documents in O(1)
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operations. If the hash index is unique, then no two documents are allowed to have the
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same set of attribute values.
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Creating a new document or updating a document will fail if the uniqueness is violated.
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If the index is declared sparse, a document will be excluded from the index and no
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uniqueness checks will be performed if any index attribute value is not set or has a value
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of `null`.
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!SECTION Accessing Hash Indexes from the Shell
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<!-- js/server/modules/org/arangodb/arango-collection.js-->
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@startDocuBlock ensureUniqueConstraint
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<!-- js/server/modules/org/arangodb/arango-collection.js-->
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@startDocuBlock ensureHashIndex
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