Fts4
@Target(allowedTargets = [AnnotationTarget.CLASS])
@Retention(value = AnnotationRetention.BINARY)
public annotation Fts4
Marks an Entity annotated class as a FTS4 entity. This class will have a mapping SQLite FTS4 table in the database.
FTS3 and FTS4 (https://www.sqlite.org/fts3.html) 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. Therefore, an FTS entity can only have a single property annotated with PrimaryKey, it must be named rowid and must be of INTEGER affinity. The property can be optionally omitted in the class but can still be used in queries.
All properties in an FTS entity are of TEXT affinity, except the for the 'rowid' and 'languageid' properties.
Example:
@Entity
@Fts4
data class Mail (
@PrimaryKey
@ColumnInfo(name = "rowid")
val rowId: Int,
val subject: String,
val body: String
)
| See also | |
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Entity |
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Dao |
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Database |
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PrimaryKey |
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ColumnInfo |
Summary
Public constructors |
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Public methods |
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final @NonNull KClass<@NonNull ?> |
The external content entity who's mapping table will be used as content for the FTS table. |
final @NonNull String |
The column name to be used as 'languageid'. |
final @NonNull FtsOptions.MatchInfo |
The FTS version used to store text matching information. |
final @NonNull String[] |
The list of column names on the FTS table that won't be indexed. |
final @NonNull FtsOptions.Order |
getOrder()The preferred 'rowid' order of the FTS table. |
final @NonNull int[] |
The list of prefix sizes to index. |
final @NonNull String |
The tokenizer to be used in the FTS table. |
final @NonNull String[] |
Optional arguments to configure the defined tokenizer. |
Public constructors
Public methods
getContentEntity
public final @NonNull KClass<@NonNull ?> getContentEntity()
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.
See the External Content FTS4 Tables documentation for details.
getLanguageId
public final @NonNull String getLanguageId()
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 property 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.
getMatchInfo
public final @NonNull FtsOptions.MatchInfo getMatchInfo()
The FTS version used to store text matching information.
The default value is FtsOptions.MatchInfo.FTS4. Disk space consumption can be reduced by setting this option to FTS3, see the matchinfo= option documentation for details.
| Returns | |
|---|---|
@NonNull FtsOptions.MatchInfo |
The match info version, either |
getNotIndexed
public final @NonNull String[] getNotIndexed()
The list of column names on the FTS table that won't be indexed.
For details, see the notindexed= option documentation.
| Returns | |
|---|---|
@NonNull String[] |
A list of column names that will not be indexed by the FTS extension. |
getOrder
public final @NonNull FtsOptions.Order getOrder()
The preferred 'rowid' order of the FTS table.
The default value is FtsOptions.Order.ASC. If many queries run against the FTS table use ORDER BY row DESC then it may improve performance to set this option to FtsOptions.Order.DESC, enabling the FTS module to store its data in a way that optimizes returning results in descending order by rowid.
| Returns | |
|---|---|
@NonNull FtsOptions.Order |
The preferred order, either |
getPrefix
public final @NonNull int[] getPrefix()
The list of prefix sizes to index.
For details, the prefix= option documentation.
| Returns | |
|---|---|
@NonNull int[] |
A list of non-zero positive prefix sizes to index. |
getTokenizer
public final @NonNull String getTokenizer()
The tokenizer to be used in the FTS table.
The default value is FtsOptions.TOKENIZER_SIMPLE. Tokenizer arguments can be defined with tokenizerArgs.
If a custom tokenizer is used, the tokenizer and its arguments are not verified at compile time.
For details, see SQLite tokernizers documentation
| Returns | |
|---|---|
@NonNull String |
The tokenizer to use on the FTS table. Built-in available tokenizers are |
getTokenizerArgs
public final @NonNull String[] getTokenizerArgs()
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 FtsOptions.TOKENIZER_UNICODE61 tokenizer.
The available arguments that can be defined depend on the tokenizer defined, see the SQLite tokenizers documentation for details.
| Returns | |
|---|---|
@NonNull String[] |
A list of tokenizer arguments strings. |