Handling Nulls

One of the core features of Quivr is its support for handling null values in data.

Data behind a Quivr table can have null values. You can explicitly permit nulls by passing a nullable=True parameter when contructing a quivr.Column. If this is not set, then any constructors of tables which provide null values will be rejected:

import quivr as qv

class MyTable(qv.Table):
    id = qv.StringColumn()

# This will raise an error:
t = MyTable.from_kwargs(id=["a", "b", None, "d"])

class MyTable2(qv.Table):
    id = qv.StringColumn(nullable=True)

# This is fine
t = MyTable2.from_kwargs(id=["a", "b", None, "d"])

Using defaults

Instead of raising an error in the presence of nulls, you can set a default that will be filled in when nulls are present.

This default value can be either a static literal value, or a callable which takes no arguments and which returns a value:

import quivr as qv
import uuid

class User(qv.Table):
    id = qv.StringColumn(default=uuid.uuidv4)
    login_attempts = qv.UInt32Column(default=0)

# This won't raise an error. Instead, it will call uuid.uuidv4()
# for each null id, and will insert '0' for each null login_attempts.
t = User.from_kwargs(
    id=["a", "b", None, "d", None],
    login_attempts=[0, 1, None, None, 3],
)

Default values will also get used if a column is omitted entirely from a constructor. For example:

# t.login_attempts will be filled with [0, 0, 0].
t = User.from_kwargs(
    id=["a", "b", "c"],
)

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