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Fields

Column(type='', name='', *, default_type='', default_expression='', comment='', codec_expression='', ttl_expression='') dataclass

Represents a ClickHouse column. Can be manually constructed or created from a pydantic.Field.

Parameters:

Name Type Description Default
type str

The ClickHouse type of the column.

 ''
name str

The name of the column.

 ''
default_type str

The default type of the column.

 ''
default_expression str

The default expression of the column.

 ''
comment str

The comment of the column.

 ''
codec_expression str

The codec expression of the column.

 ''
ttl_expression str

The TTL expression of the column.

 ''

Examples:

>>> Column(type="String", name="name")
Column(type='String', name='name', default_type='', default_expression='', comment='', codec_expression='', ttl_expression='')

from_field(name, info) classmethod

Create a Column instance from a pydantic.Field.

Parameters:

Name Type Description Default
name str

Name of the column.

 required
info FieldInfo

pydantic.FieldInfo instance.

 required

from_sql(**kwargs) classmethod

Create a Column instance from a SQL column definition.

Parameters:

Name Type Description Default
**kwargs Any

Column definition keyword arguments.

 {}

to_sql()

Convert the column to a SQL column definition.

Returns:

Type Description
str

SQL column definition as a string.

Expression(value)

ClickHouse Query expression with support for operations.

Accessing the columns on a table returns an Expression object.

Supports the following operations
  • Arithmetic: +, -, *, /
  • Comparison: <, <=, >, >=, ==, !=
  • Logical: &&, ||
  • Negation: !
  • Unary: +, -
  • Containment: in, not_in

Examples:

>>> Expression("column") + 1
column + 1
>>> Expression("column") > Expression("other)
column > other
>>> Expression("column").is_in([1, 2, 3])
column | in [1, 2, 3]

Function(name, *args)

ClickHouse dynamic function used in queries as fallback for PRQL expressions.

Created using the F object. Used to created PRQL s-strings.

Examples:

>>> Function("sum", "value").to_sql()
s'sum(value)'
>>> Function(F.toDate(column)).to_sql()
s'toDate(column)'

Aggregate(value)

ClickHouse Aggregate function used in group and window pipelines.

Used to distinguish between aggregate and non-aggregate expressions in group and and window.

Examples:

>>> Aggregate("value")
Aggregate(value)
>>> Aggregate(F.sum("value"))
Aggregate(sum(value))

Param(name, type=str)

ClickHouse parameter used in queries for parameterized values.

Requires a type for the parameter, which is used by ClickHouse to infer the type of the parameter.

Parameters:

Name Type Description Default
name str

Name of the parameter.

 required
type type

ClickHouse type. Defaults to str.

 str

Examples:

>>> Param("name", str)
Param(name, str)
>>> str(Param("name", str))
{{ name:String }}

Window(*, range=None, rows=None)

ClickHouse window specification used in window pipelines.

Parameters:

Name Type Description Default
range tuple[int | None, int | None] | None

tuple of (start, end) for range window. Start and end can be None, which represents unbounded. Cannot be specified with rows.

 None
rows tuple[int | None, int | None] | None

tuple of (start, end) for rows window. Start and end can be None, which represents unbounded. Cannot be specified with range.

 None