- * Notes about concurrent access to the taxonomy: - *
- * An implementation must allow multiple readers and a single writer to be - * active concurrently. Readers follow so-called "point in time" semantics, - * i.e., a reader object will only see taxonomy entries which were available - * at the time it was created. What the writer writes is only available to - * (new) readers after the writer's commit() is called. - *
- * Faceted search keeps two indices - namely Lucene's main index, and this - * taxonomy index. When one or more readers are active concurrently with the - * writer, care must be taken to avoid an inconsistency between the state of - * these two indices: When writing to the indices, the taxonomy must always - * be committed to disk *before* the main index, because the main index - * refers to categories listed in the taxonomy. - * Such control can best be achieved by turning off the main index's - * "autocommit" feature, and explicitly calling commit() for both indices - * (first for the taxonomy, then for the main index). - * In old versions of Lucene (2.2 or earlier), when autocommit could not be - * turned off, a more complicated solution needs to be used. E.g., use - * some sort of (possibly inter-process) locking to ensure that a reader - * is being opened only right after both indices have been flushed (and - * before anything else is written to them). - * - * @lucene.experimental - */ -public interface TaxonomyWriter extends Closeable { - - /** - * addCategory() adds a category with a given path name to the taxonomy, - * and returns its ordinal. If the category was already present in - * the taxonomy, its existing ordinal is returned. - *
- * Before adding a category, addCategory() makes sure that all its
- * ancestor categories exist in the taxonomy as well. As result, the
- * ordinal of a category is guaranteed to be smaller then the ordinal of
- * any of its descendants.
- */
- public int addCategory(CategoryPath categoryPath) throws IOException;
-
- /**
- * Calling commit() ensures that all the categories written so far are
- * visible to a reader that is opened (or reopened) after that call.
- * When the index is closed(), commit() is also implicitly done.
- */
- public void commit() throws IOException;
-
- /**
- * Like commit(), but also store properties with the index. These properties
- * are retrievable by {@link TaxonomyReader#getCommitUserData}.
- * See {@link IndexWriter#commit(Map)}.
- */
- public void commit(Map
- * When a category is specified as a path name, finding the path of its
- * parent is as trivial as dropping the last component of the path.
- * getParent() is functionally equivalent to calling getPath() on the
- * given ordinal, dropping the last component of the path, and then calling
- * getOrdinal() to get an ordinal back.
- *
- * If the given ordinal is the ROOT_ORDINAL, an INVALID_ORDINAL is returned.
- * If the given ordinal is a top-level category, the ROOT_ORDINAL is returned.
- * If an invalid ordinal is given (negative or beyond the last available
- * ordinal), an ArrayIndexOutOfBoundsException is thrown. However, it is
- * expected that getParent will only be called for ordinals which are
- * already known to be in the taxonomy.
- *
- * TODO (Facet): instead of a getParent(ordinal) method, consider having a
- * getCategory(categorypath, prefixlen) which is similar to addCategory
- * except it doesn't add new categories; This method can be used to get
- * the ordinals of all prefixes of the given category, and it can use
- * exactly the same code and cache used by addCategory() so it means less code.
- */
- public int getParent(int ordinal) throws IOException;
-
- /**
- * getSize() returns the number of categories in the taxonomy.
- *
- * Because categories are numbered consecutively starting with 0, it
- * means the taxonomy contains ordinals 0 through getSize()-1.
- *
- * Note that the number returned by getSize() is often slightly higher
- * than the number of categories inserted into the taxonomy; This is
- * because when a category is added to the taxonomy, its ancestors
- * are also added automatically (including the root, which always get
- * ordinal 0).
- */
- public int getSize();
-
-}