mirror of https://gitee.com/bigwinds/arangodb
34 lines
1.4 KiB
Plaintext
34 lines
1.4 KiB
Plaintext
!CHAPTER Cap Constraint
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!SUBSECTION Introduction to Cap Constraints
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This is an introduction to ArangoDB's size restrictions aka cap constraints for
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collections.
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It is possible to restrict the size of collections. If you add a document and
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the size exceeds the limit, then the least recently created or updated document(s)
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will be dropped. The size of a collection is measured in the number of
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active documents a collection contains, and optionally in the total size of
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the active documents' data in bytes.
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It is possible to only restrict the number of documents in a collection, or to
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only restrict the total active data size, or both at the same time. If there are
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restrictions on both document count and total size, then the first violated
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constraint will trigger the auto-deletion of "too" old documents until all
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constraints are satisfied.
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Using a cap constraint, a collection can be used as a FIFO container, with just
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the newest documents remaining in the collection.
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For example, a cap constraint can be used to keep a list of just the most recent
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log entries, and at the same time ensure that the collection does not grow
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indefinitely. Cap constraints can be used to automate the process of getting rid
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of "old" documents, and so save the user from implementing own jobs to purge
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"old" collection data.
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!SECTION Accessing Cap Constraints from the Shell
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<!-- js/server/modules/org/arangodb/arango-collection.js-->
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@startDocuBlock collectionEnsureCapConstraint
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