Database file optimization

Avoid database schema changes.

If possible, avoid changing the schema (table structure) of a database once you’ve added data into the database’s tables. Normally a database file is structured with the table definitions at the start of the file. When you open a connection to a database, the runtime loads those definitions. When you add data to database tables, that data is added to the file after the table definition data. However, if you make schema changes, the new table definition data is mixed in with the table data in the database file. For example, adding a column to a table or adding a new table can result in the mixing of types of data. If the table definition data is not all located at the beginning of the database file, it takes longer to open a connection to the database. The connection is slower to open because it takes the runtime longer to read the table definition data from different parts of the file.

Use the SQLConnection.compact() method to optimize a database after schema changes.

If you must make schema changes, you can call the SQLConnection.compact() method after completing the changes. This operation restructures the database file so that the table definition data is located together at the start of the file. However, the compact() operation can be time-intensive, especially as a database file grows larger.

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