mnemosine.schema.index_json_attribute

Kind: function

Signature

index_json_attribute(conn, attr: str, as_type: str='TEXT') -> str

Documentation

Materialize a metadata JSON attribute as a generated column plus index.

Adds a VIRTUAL generated column to nodes that extracts metadata.attr (using json_extract) and creates an index on it, so WHERE metadata->'attr' = ... style queries can use the index. Safe to call repeatedly: existing columns and indexes are left untouched.

Args:

• conn (sqlite3.Connection): An open connection to the database.
• attr (str): The metadata attribute to index.
• as_type (str): SQL type for the column: TEXT, INTEGER,
• REAL or BLOB. Defaults to TEXT.

Returns:

• str: The name of the generated column (<attr>_gen).

Raises:

• ValueError: If as_type is not one of TEXT/INTEGER/
• REAL/BLOB.

Example:

>>> from mnemosine import Storage
>>> with Storage(":memory:") as db:
...     db.node(kind="doc").update(n=1).save()
...     db.node(kind="doc").update(n=2).save()
...     col = db.index_attribute("n", as_type="INTEGER")
...     db.conn.execute(f"SELECT count(*) FROM nodes WHERE {col} > 1").fetchone()[0]
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