| 1 | package com.hammurapi.store; |
| 2 | |
| 3 | import java.util.Comparator; |
| 4 | |
| 5 | import com.hammurapi.extract.Extractor; |
| 6 | import com.hammurapi.extract.Predicate; |
| 7 | |
| 8 | /** |
| 9 | * Store.addIndex() returns object which implements one or |
| 10 | * more of Index sub-interfaces. Index instances are used |
| 11 | * to directly leverage index functionality without going through |
| 12 | * Store.get() methods. |
| 13 | * @author Pavel Vlasov |
| 14 | * |
| 15 | * This interface extends Iterable. Iterator returned by index |
| 16 | * iterates over objects in the store which match index predicate |
| 17 | * and in the order, if the index is ordered. Iteration over indices shall be |
| 18 | * performed within store's read lock. |
| 19 | * @param <T> |
| 20 | */ |
| 21 | public interface Index<T,PK,V,S extends Store<T,PK,S>> extends Iterable<T> { |
| 22 | |
| 23 | enum Type { |
| 24 | /** |
| 25 | * Unique index is evaluated as part of insert/update (synchronously). |
| 26 | * If uniqueness is violated, exception is thrown and insert/update is |
| 27 | * not executed. |
| 28 | */ |
| 29 | UNIQUE, |
| 30 | /** |
| 31 | * Synchronous indices as evaluated as part of insert/update (by writer). |
| 32 | * If index extractor throws an exception, this exception is propagated |
| 33 | * to the caller and insert/update operation doesn't get executed. |
| 34 | */ |
| 35 | SYNCHRONOUS, |
| 36 | /** |
| 37 | * Asynchronous index modifications get evaluated in a separate task. |
| 38 | * If reader accesses the index before the index update task goes to |
| 39 | * execution, index update is performed as part of the access operation (by reader). |
| 40 | * If index extractor throws exception, then index gets marked as |
| 41 | * corrupted and is removed from the store. If the reader |
| 42 | * accesses the index directly through one of index interfaces, |
| 43 | * then the exception is propagated to the caller code. |
| 44 | * All operations on a corrupted index result in exception. |
| 45 | */ |
| 46 | ASYNCHRONOUS, |
| 47 | /** |
| 48 | * Lazy index modifications get queued and are evaluated |
| 49 | * as part of the access operation (by reader). If index |
| 50 | * extractor throws exception, then index gets marked as |
| 51 | * corrupted and is removed from the store. If the reader |
| 52 | * accesses the index directly through one of index interfaces, |
| 53 | * then the exception is propagated to the caller code. |
| 54 | * All operations on a corrupted index result in exception. |
| 55 | */ |
| 56 | LAZY |
| 57 | |
| 58 | } |
| 59 | |
| 60 | /** |
| 61 | * @return Back-link to the store. |
| 62 | */ |
| 63 | S getStore(); |
| 64 | |
| 65 | Predicate<T,S> getPredicate(); |
| 66 | |
| 67 | Extractor<T, V, S> getExtractor(); |
| 68 | |
| 69 | boolean isUnique(); |
| 70 | |
| 71 | boolean isOrdered(); |
| 72 | |
| 73 | Comparator<V> getComparator(); |
| 74 | } |