Expression Functions

Overview

Import from krishiv.functions or krishiv.sql.functions:

from krishiv.functions import col, lit, sum, avg, count, expr
from krishiv.sql.functions import upper, lower, date_trunc, coalesce

Function	Signature	Description
`col(name)`	`col(name: str) -> Column`	Reference a column by name.
`column(name)`	`column(name: str) -> Column`	Alias for `col`.
`lit(value)`	`lit(value: Any) -> Column`	Constant literal value (int, float, str, bool, None).
`expr(sql)`	`expr(sql: str) -> Column`	Parse a SQL expression string into a Column.
`call_function(name, *args)`	`Column`	Call a named SQL function or UDF with Column arguments.
`function(name, *args)`	`Column`	Alias for `call_function`.

Function	Description
`count(col='*')`	Count rows or non-null values of a column.
`count_all()`	COUNT(*) — count all rows.
`sum(col)`	Sum of numeric values.
`avg(col)`	Arithmetic mean.
`mean(col)`	Alias for `avg`.
`min(col)`	Minimum value.
`max(col)`	Maximum value.

Function	Description
`coalesce(*cols)`	Return the first non-null value.
`ifnull(value, replacement)`	Return `replacement` if `value` is null.
`nullif(left, right)`	Return null if `left == right`, else `left`.
`isnull(col)`	True if the column is null.
`isnotnull(col)`	True if the column is not null.
`isnan(col)`	True if the value is NaN.

Function	Description
`upper(col)`	Convert to uppercase.
`lower(col)`	Convert to lowercase.
`length(col)`	String length (character count).
`trim(col)`	Strip leading and trailing whitespace.
`ltrim(col)`	Strip leading whitespace.
`rtrim(col)`	Strip trailing whitespace.
`concat(*cols)`	Concatenate strings.

Function	Description
`abs(col)`	Absolute value.
`round(col, scale=0)`	Round to `scale` decimal places.
`floor(col)`	Floor (round down to integer).
`ceil(col)`	Ceiling (round up to integer).
`sqrt(col)`	Square root.
`exp(col)`	e raised to the power of `col`.
`log(col)`	Natural logarithm.
`sin(col)`	Sine (radians).
`cos(col)`	Cosine (radians).
`tan(col)`	Tangent (radians).

Function	Description
`current_date()`	Current date (evaluates at query planning time).
`current_timestamp()`	Current timestamp.
`date_trunc(unit, timestamp)`	Truncate to a time unit ('year', 'month', 'day', 'hour', 'minute', 'second').

Function	Description
`asc(col)`	Wrap column in ascending sort order.
`desc(col)`	Wrap column in descending sort order.
`cast(col, data_type)`	Cast column to `data_type` string (e.g. `'int64'`, `'utf8'`).
`try_cast(col, data_type)`	Cast returning null on failure instead of erroring.