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Administrating MarkLogic Server

Legacy Assignment Policy

After upgrading to MarkLogic 7.0 or a later version, existing databases will be configured with the rebalancer disabled and the legacy assignment policy. This is to preserve the expected behavior when new documents are loaded into the database.

Note

Under most circumstances you would not use the legacy policy when the database rebalancer is enabled. The segment policy, described in Segment Assignment Policy, is generally preferred over the legacy policy.

The legacy policy uses the URI of a document to decide which forest the document should be assigned to. The mapping from a URI to a forest uses the same algorithm as the one used on older releases of MarkLogic Server.

For example, as shown in the figure below, a new forest, ForestD, is added to the database that already has three forests: ForestA, ForestB, and ForestC, each contains 400 documents because the document URIs allow for even distribution of them among the forests. The data is rebalanced as follows:

  • ForestA moves 100 documents to ForestB

  • ForestB moves 200 documents to ForestC

  • ForestC moves 300 documents to ForestD

Fgure showing a new forest, ForestD, added to the database that already has three forests: ForestA, ForestB, and ForestC, each contains 400 documents because the document URIs allow for even distribution of them among the forests.

The legacy policy is the least efficient rebalancer policy, as it requires the greatest amount of document movement to rebalance the documents among the forests. For this reason, you should only use the legacy policy on legacy databases with the rebalancer disabled.

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