Cursor

Cursor objects represents real Cursor in the PostgreSQL. PostgreSQL docs It can be built only from Transaction.

Cursor Parameters

• querystring: specify query for cursor.
• parameters: parameters for the querystring. Default None
• fetch_number: default fetch number. It is used in fetch() method and in async iterator. Default 10
• scroll: is cursor scrollable or not. Default as in PostgreSQL.

Cursor as async iterator

The most common situation is using Cursor as async iterator.

from psqlpy import ConnectionPool, QueryResult


async def main() -> None:
    db_pool = ConnectionPool()


    connection = await db_pool.connection()
    transaction = await connection.transaction()

    # Here we fetch 5 results in each iteration.
    async with cursor in transaction.cursor(
        querystring="SELECT * FROM users WHERE username = $1",
        parameters=["Some_Username"],
        fetch_number=5,
    ):
        async for fetched_result in cursor:
            dict_result: List[Dict[Any, Any]] = fetched_result.result()
            ... # do something with this result.

Cursor methods

There are a lot of methods to work with cursor.

Start

Declare (create) cursor.

async def main() -> None:
    await cursor.start()

Close

Close the cursor

async def main() -> None:
    await cursor.close()

Fetch

You can fetch next N records from the cursor. It's possible to specify N fetch record with parameter fetch_number, otherwise will be used fetch_number from the Cursor initialization.

async def main() -> None:
    result: QueryResult = await cursor.fetch(
        fetch_number=100,
    )

Fetch Next

Just fetch next record from the Cursor.

async def main() -> None:
    result: QueryResult = await cursor.fetch_next()

Fetch Prior

Just fetch previous record.

async def main() -> None:
    result: QueryResult = await cursor.fetch_prior()

Fetch First

Just fetch the first record.

async def main() -> None:
    result: QueryResult = await cursor.fetch_first()

Fetch Last

Just fetch the last record.

async def main() -> None:
    result: QueryResult = await cursor.fetch_last()

Fetch Absolute

Just fetch absolute records. It has absolute_number parameter, you must specify it.

async def main() -> None:
    result: QueryResult = await cursor.fetch_absolute(
        absolute_number=10,
    )

Fetch Relative

Just fetch absolute records. It has relative_number parameter, you must specify it.

async def main() -> None:
    result: QueryResult = await cursor.fetch_relative(
        relative_number=10,
    )

Fetch Forward All

Fetch forward all records in the cursor.

async def main() -> None:
    result: QueryResult = await cursor.fetch_forward_all()

Fetch Backward

Just backward records. It has backward_count parameter, you must specify it.

async def main() -> None:
    result: QueryResult = await cursor.fetch_backward(
        backward_count=10,
    )

Fetch Backward All

Fetch backward all records in the cursor.

async def main() -> None:
    result: QueryResult = await cursor.fetch_backward_all()