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Last edited by Hugo Beauzée-Luyssen

This section describes the helpers exposed by the SqliteTools.h header

Row

This class simplifies accessing a row from the database, and is used by all entities classes to construct an instance based on a database record.

This helpers can either be used to extract some specific columns at a given index (using the Row::load(uint32_t idx) accessor, or can be used to extract columns one after another using the Row::extract() accessor.

All accessors are templated and expect to be provided the type of the column being accessed.

In addition this class exposes a few accessors to provide insight about the number of column in the row.

It also exposes a comparison operator with nullptr_t which is expected to be used when iterating over rows in a result set:

Row sqliteRow;
while ( ( sqliteRow = stmt.row() ) != nullptr )
{
...
}

Statement

This class essentially wraps the raw sqlite3_stmt types and provides automatic management for a compiled statement.

It also contains a statements cache and the entry point for place holders bindings.

When a Statement gets constructed, its constructor will attempt to fetch an already compiled statement for that request. If it hasn't been compiled yet, it will do so and cache the resulting compiled statement in its cache for later use.

Tools

This class is responsible for creating or fetching the entities from the database, and connects the Statement & Row helpers together.

It provides the following operations:

  • fetchAll which fetches N entities from the database, based on the provided request.
  • fetchOne will fetch a single entity from the database
  • executeRequest executes a request and performs no particular check or treatment.
  • executeDelete will execute a deletion request by invoking executeRequest but returns false if a sporadic error is detected.
  • executeUpdate is identical to executeDelete but is provided as a self-documenting accessor, should the user want to execute an UPDATE instead of a DELETE
  • executeInsert executes an insertion request and returns the newly created row primary key, or 0 in case of error.
  • checkTriggerStatement ensures that a trigger statement in database is the same as the provided one. This is used to ensure migrations are correctly executed
  • checkIndexStatement does the same as checkTriggerStatement but for indexes.
  • checkTableSchem ensures a table schema in database is the expected one. This is also used to ensure migrations were successful.
  • listTables will list all known tables from the database, excluding sqlite's internal tables
  • sanitizePattern provides a minimal escaping for search patterns

Please bear in mind that no check is performed on the actual request, meaning that you can pass a SELECT ... request to executeDelete, but the prototypes ensure that you will not be able to do anything meaningful with the results.

The fetch & executeXXXX helpers will also acquire a read or write context respectively if no context was opened for the calling thread (see https://code.videolan.org/videolan/medialibrary/-/wikis/doc/sqlite/Thread-model)

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