* FTS3 and FTS4 are SQLite virtual table modules * that allows full-text searches to be performed on a set of documents. *
* An FTS entity table always has a column named rowid that is the equivalent of an
* INTEGER PRIMARY KEY index. Therefore, an FTS entity can only have a single field
* annotated with {@link PrimaryKey}, it must be named rowid and must be of
* INTEGER affinity. The field can be optionally omitted in the class but can still be
* used in queries.
*
* All fields in an FTS entity are of TEXT affinity, except the for the 'rowid' and
* 'languageid' fields.
*
* Example: *
* {@literal @}Entity
* {@literal @}Fts4
* public class Mail {
* {@literal @}PrimaryKey
* {@literal @}ColumnInfo(name = "rowid")
* private final int rowId;
* private final String subject;
* private final String body;
*
* public Mail(int rowId, String subject, String body) {
* this.rowId = rowId;
* this.subject = subject;
* this.body = body;
* }
*
* public String getRowId() {
* return rowId;
* }
* public String getSubject() {
* return subject;
* }
* public void getBody() {
* return body;
* }
* }
*
*
* @see Entity
* @see Dao
* @see Database
* @see PrimaryKey
* @see ColumnInfo
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.CLASS)
@RequiresApi(16)
public @interface Fts4 {
/**
* The tokenizer to be used in the FTS table.
* * The default value is {@link FtsOptions#TOKENIZER_SIMPLE}. Tokenizer arguments can be defined * with {@link #tokenizerArgs()}. *
* If a custom tokenizer is used, the tokenizer and its arguments are not verified at compile * time. * * @return The tokenizer to use on the FTS table. Built-in available tokenizers are * {@link FtsOptions#TOKENIZER_SIMPLE}, {@link FtsOptions#TOKENIZER_PORTER} and * {@link FtsOptions#TOKENIZER_UNICODE61}. * @see #tokenizerArgs() * @see SQLite tokernizers * documentation */ String tokenizer() default TOKENIZER_SIMPLE; /** * Optional arguments to configure the defined tokenizer. *
* Tokenizer arguments consist of an argument name, followed by an "=" character, followed by
* the option value. For example, separators=. defines the dot character as an
* additional separator when using the {@link FtsOptions#TOKENIZER_UNICODE61} tokenizer.
*
* The available arguments that can be defined depend on the tokenizer defined, see the * SQLite tokernizers documentation for * details. * * @return A list of tokenizer arguments strings. */ String[] tokenizerArgs() default {}; /** * The external content entity who's mapping table will be used as content for the FTS table. *
* Declaring this value makes the mapping FTS table of this entity operate in "external content" * mode. In such mode the FTS table does not store its own content but instead uses the data in * the entity mapped table defined in this value. This option allows FTS4 to forego storing the * text being indexed which can be used to achieve significant space savings. *
* In "external mode" the content table and the FTS table need to be synced. Room will create * the necessary triggers to keep the tables in sync. Therefore, all write operations should * be performed against the content entity table and not the FTS table. *
* The content sync triggers created by Room will be removed before migrations are executed and * are re-created once migrations are complete. This prevents the triggers from interfering with * migrations but means that if data needs to be migrated then write operations might need to be * done in both the FTS and content tables. * * @return The external content entity. * @see External * Content FTS4 Tables */ Class contentEntity() default Object.class; /** * The column name to be used as 'languageid'. *
* Allows the FTS4 extension to use the defined column name to specify the language stored in
* each row. When this is defined a field of type INTEGER with the same name must
* exist in the class.
*
* FTS queries are affected by defining this option, see * the languageid= option * documentation for details. * * @return The column name to be used as 'languageid'. */ String languageId() default ""; /** * The FTS version used to store text matching information. *
* The default value is {@link MatchInfo#FTS4}. Disk space consumption can be reduced by * setting this option to FTS3, see * the matchinfo= option * documentation for details. * * @return The match info version, either {@link MatchInfo#FTS4} or {@link MatchInfo#FTS3}. */ MatchInfo matchInfo() default MatchInfo.FTS4; /** * The list of column names on the FTS table that won't be indexed. * * @return A list of column names that will not be indexed by the FTS extension. * @see The notindexed= option * documentation */ String[] notIndexed() default {}; /** * The list of prefix sizes to index. * * @return A list of non-zero positive prefix sizes to index. * @see The prefix= option * documentation */ int[] prefix() default {}; /** * The preferred 'rowid' order of the FTS table. *
* The default value is {@link Order#ASC}. If many queries are run against the FTS table use
* ORDER BY row DESC then it may improve performance to set this option to
* {@link Order#DESC}, enabling the FTS module to store its data in a way that optimizes
* returning results in descending order by rowid.
*
* @return The preferred order, either {@link Order#ASC} or {@link Order#DESC}.
*/
Order order() default Order.ASC;
}