Getting Row ID from SQLite FTS3 Tables
SQLite’s FTS3 (Full Text Search) extension provides a powerful way to search through textual data within your database. However, retrieving the row ID of matching entries can sometimes be tricky. This article will guide you through different approaches to achieve this efficiently.
Methods for Retrieving Row IDs
1. Using the ‘rowid’ Column
In a regular SQLite table, you can directly access the row ID using the rowid column. However, FTS3 tables function differently. The rowid column in an FTS3 table does not hold the original row ID of the document. Instead, it serves as a unique identifier for the entry within the FTS3 table itself.
Example:
CREATE VIRTUAL TABLE my_fts_table USING FTS3;
INSERT INTO my_fts_table VALUES ('Document 1', 'This is the first document.');
INSERT INTO my_fts_table VALUES ('Document 2', 'Here is the second document.');
SELECT rowid, * FROM my_fts_table WHERE my_fts_table MATCH 'document';
rowid|docid|content
-----|------|----------
1 |1 |Document 1
2 |2 |Document 2
In this example, the rowid column reflects the entry’s order within the FTS3 table, not the corresponding row ID in the original table.
2. Using the ‘docid’ Column
To retrieve the original row ID of a document, you need to rely on the docid column. This column stores the row ID from the original table where the document content originates.
Example:
CREATE VIRTUAL TABLE my_fts_table USING FTS3;
INSERT INTO my_fts_table VALUES ('Document 1', 'This is the first document.');
INSERT INTO my_fts_table VALUES ('Document 2', 'Here is the second document.');
SELECT docid, * FROM my_fts_table WHERE my_fts_table MATCH 'document';
docid|rowid|content
-----|------|----------
1 |1 |Document 1
2 |2 |Document 2
Here, the docid column correctly reflects the row IDs of the original documents.
Additional Considerations
Remember that the ‘docid’ column can only be used when you’re retrieving data from the FTS3 table. If you’re performing a query directly on the original table, the ‘rowid’ column remains the standard way to access the unique ID of each row.
Moreover, when working with multiple FTS3 tables that might reference the same original table, you should carefully manage the ‘docid’ column to ensure consistency.
Conclusion
By understanding the unique characteristics of FTS3 tables and utilizing the ‘docid’ column, you can easily retrieve the row ID of matching entries from the original table. This enables you to efficiently link the results of your text searches with the specific records in your database.