Python库 | Products.ZCatalog-4.3.tar.gz

CompositeIndex README Overview CompositeIndex is a plugin index for the ZCatalog. Indexes containing more than one attribute to index an object are called “composite index”. Such indexes should be created if you expect to run queries that will have multiple attributes in the search phrase and all attributes combined will give significantly less hits than the any of the attributes alone. The key of a composite index is called “composite key” and is composed of two or more attributes of an object. Catalog queries containing attributes managed by CompositeIndex are transparently catched and transformed seamlessly into a CompositeIndex query. In particular, large sites with a combination of additional indexes (FieldIndex, KeywordIndex, BooleanIndex) and lots of content (>100k) will profit. The expected performance enhancement for combined index queries is about a factor of >2-3. For example many catalog queries in plone are based on the combination of indexed attributes as follows: 'Language', 'review_state', 'portal_type' and 'allowedRolesAndUsers'. Normally, the ZCatalog sequentially executes each corresponding atomic index and calculates intersection between each result. This strategy, in particular for large sites, decreases the performance of the catalog and simultaneously increases the volatility of ZODB’s object cache, because each index individually has a high number of hits whereas the the intersection between each index result has a low number of hits. CompositeIndex overcomes this difficulty because it already contains a pre-calculateted intersection by means of its composite keys. The loading of large sets and the following expensive computation of the intersection is therefore obsolete. IMPORTANT: CompositeIndex can only be used as an add-on not as a replacement for field, keyword and boolean indexes.