Compute Functions#
The generic Compute API#
Functions and function registry#
Functions represent compute operations over inputs of possibly varying types. Internally, a function is implemented by one or several “kernels”, depending on the concrete input types (for example, a function adding values from two inputs can have different kernels depending on whether the inputs are integral or floating-point).
Functions are stored in a global FunctionRegistry
where
they can be looked up by name.
Input shapes#
Computation inputs are represented as a general Datum
class,
which is a tagged union of several shapes of data such as Scalar
,
Array
and ChunkedArray
. Many compute functions support
both array (chunked or not) and scalar inputs, however some will mandate
particular input types. For example, while array_sort_indices
requires its
first and only input to be an array, the generalized sort_indices
function accepts an array, chunked array, record batch or table.
Invoking functions#
Compute functions can be invoked by name using
arrow::compute::CallFunction()
:
std::shared_ptr<arrow::Array> numbers_array = ...;
std::shared_ptr<arrow::Scalar> increment = ...;
arrow::Datum incremented_datum;
ARROW_ASSIGN_OR_RAISE(incremented_datum,
arrow::compute::CallFunction("add", {numbers_array, increment}));
std::shared_ptr<Array> incremented_array = std::move(incremented_datum).make_array();
(note this example uses implicit conversion from std::shared_ptr<Array>
to Datum
)
Many compute functions are also available directly as concrete APIs, here
arrow::compute::Add()
:
std::shared_ptr<arrow::Array> numbers_array = ...;
std::shared_ptr<arrow::Scalar> increment = ...;
arrow::Datum incremented_datum;
ARROW_ASSIGN_OR_RAISE(incremented_datum,
arrow::compute::Add(numbers_array, increment));
std::shared_ptr<Array> incremented_array = std::move(incremented_datum).make_array();
Some functions accept or require an options structure that determines the exact semantics of the function:
ScalarAggregateOptions scalar_aggregate_options;
scalar_aggregate_options.skip_nulls = false;
std::shared_ptr<arrow::Array> array = ...;
arrow::Datum min_max;
ARROW_ASSIGN_OR_RAISE(min_max,
arrow::compute::CallFunction("min_max", {array},
&scalar_aggregate_options));
// Unpack struct scalar result (a two-field {"min", "max"} scalar)
std::shared_ptr<arrow::Scalar> min_value, max_value;
min_value = min_max.scalar_as<arrow::StructScalar>().value[0];
max_value = min_max.scalar_as<arrow::StructScalar>().value[1];
However, Grouped Aggregations are
not invocable via CallFunction
.
See also
Implicit casts#
Functions may require conversion of their arguments before execution if a kernel does not match the argument types precisely. For example comparison of dictionary encoded arrays is not directly supported by any kernel, but an implicit cast can be made allowing comparison against the decoded array.
Each function may define implicit cast behaviour as appropriate. For example comparison and arithmetic kernels require identically typed arguments, and support execution against differing numeric types by promoting their arguments to numeric type which can accommodate any value from either input.
Common numeric type#
The common numeric type of a set of input numeric types is the smallest numeric type which can accommodate any value of any input. If any input is a floating point type the common numeric type is the widest floating point type among the inputs. Otherwise the common numeric type is integral and is signed if any input is signed. For example:
Input types |
Common numeric type |
Notes |
---|---|---|
int32, int32 |
int32 |
|
int16, int32 |
int32 |
Max width is 32, promote LHS to int32 |
uint16, int32 |
int32 |
One input signed, override unsigned |
uint32, int32 |
int64 |
Widen to accommodate range of uint32 |
uint16, uint32 |
uint32 |
All inputs unsigned, maintain unsigned |
int16, uint32 |
int64 |
|
uint64, int16 |
int64 |
int64 cannot accommodate all uint64 values |
float32, int32 |
float32 |
Promote RHS to float32 |
float32, float64 |
float64 |
|
float32, int64 |
float32 |
int64 is wider, still promotes to float32 |
In particular, note that comparing a uint64
column to an int16
column
may emit an error if one of the uint64
values cannot be expressed as the
common type int64
(for example, 2 ** 63
).
Available functions#
Type categories#
To avoid exhaustively listing supported types, the tables below use a number of general type categories:
“Numeric”: Integer types (Int8, etc.) and Floating-point types (Float32, Float64, sometimes Float16). Some functions also accept Decimal128 and Decimal256 input.
“Temporal”: Date types (Date32, Date64), Time types (Time32, Time64), Timestamp, Duration, Interval.
“Binary-like”: Binary, LargeBinary, sometimes also FixedSizeBinary.
“String-like”: String, LargeString.
“List-like”: List, LargeList, ListView, LargeListView, and sometimes also FixedSizeList.
“Nested”: List-likes (including FixedSizeList), Struct, Union, and related types like Map.
If you are unsure whether a function supports a concrete input type, we
recommend you try it out. Unsupported input types return a TypeError
Status
.
Aggregations#
Scalar aggregations operate on a (chunked) array or scalar value and reduce the input to a single output value.
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
all |
Unary |
Boolean |
Scalar Boolean |
(1) |
|
any |
Unary |
Boolean |
Scalar Boolean |
(1) |
|
approximate_median |
Unary |
Numeric |
Scalar Float64 |
||
count |
Unary |
Any |
Scalar Int64 |
(2) |
|
count_all |
Nullary |
Scalar Int64 |
|||
count_distinct |
Unary |
Non-nested types |
Scalar Int64 |
(2) |
|
first |
Unary |
Numeric, Binary |
Scalar Input type |
(11) |
|
first_last |
Unary |
Numeric, Binary |
Scalar Struct |
(11) |
|
index |
Unary |
Any |
Scalar Int64 |
(3) |
|
last |
Unary |
Numeric, Binary |
Scalar Input type |
(11) |
|
max |
Unary |
Non-nested types |
Scalar Input type |
||
mean |
Unary |
Numeric |
Scalar Decimal/Float64 |
(4) |
|
min |
Unary |
Non-nested types |
Scalar Input type |
||
min_max |
Unary |
Non-nested types |
Scalar Struct |
(5) |
|
mode |
Unary |
Numeric |
Struct |
(6) |
|
product |
Unary |
Numeric |
Scalar Numeric |
(7) |
|
quantile |
Unary |
Numeric |
Scalar Numeric |
(8) |
|
stddev |
Unary |
Numeric |
Scalar Float64 |
(9) |
|
sum |
Unary |
Numeric |
Scalar Numeric |
(7) |
|
tdigest |
Unary |
Numeric |
Float64 |
(10) |
|
variance |
Unary |
Numeric |
Scalar Float64 |
(9) |
(1) If null values are taken into account, by setting the ScalarAggregateOptions parameter skip_nulls = false, then Kleene logic logic is applied. The min_count option is not respected.
(2) CountMode controls whether only non-null values are counted (the default), only null values are counted, or all values are counted.
(3) Returns -1 if the value is not found. The index of a null value is always -1, regardless of whether there are nulls in the input.
(4) For decimal inputs, the resulting decimal will have the same precision and scale. The result is rounded away from zero.
(5) Output is a
{"min": input type, "max": input type}
Struct.Of the interval types, only the month interval is supported, as the day-time and month-day-nano types are not sortable.
(6) Output is an array of
{"mode": input type, "count": Int64}
Struct. It contains the N most common elements in the input, in descending order, where N is given inModeOptions::n
. If two values have the same count, the smallest one comes first. Note that the output can have less than N elements if the input has less than N distinct values.(7) Output is Int64, UInt64, Float64, or Decimal128/256, depending on the input type.
(8) Output is Float64 or input type, depending on QuantileOptions.
(9) Decimal arguments are cast to Float64 first.
(10) tdigest/t-digest computes approximate quantiles, and so only needs a fixed amount of memory. See the reference implementation for details.
(11) Result is based on the ordering of input data
Decimal arguments are cast to Float64 first.
Grouped Aggregations (“group by”)#
Grouped aggregations are not directly invokable, but are used as part of a SQL-style “group by” operation. Like scalar aggregations, grouped aggregations reduce multiple input values to a single output value. Instead of aggregating all values of the input, however, grouped aggregations partition the input values on some set of “key” columns, then aggregate each group individually, emitting one output value per input group.
As an example, for the following table:
Column |
Column |
---|---|
“a” |
2 |
“a” |
5 |
“b” |
null |
“b” |
null |
null |
null |
null |
9 |
we can compute a sum of the column x
, grouped on the column key
.
This gives us three groups, with the following results. Note that null is
treated as a distinct key value.
Column |
Column |
---|---|
“a” |
7 |
“b” |
null |
null |
9 |
The supported aggregation functions are as follows. All function names are
prefixed with hash_
, which differentiates them from their scalar
equivalents above and reflects how they are implemented internally.
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
hash_all |
Unary |
Boolean |
Boolean |
(1) |
|
hash_any |
Unary |
Boolean |
Boolean |
(1) |
|
hash_approximate_median |
Unary |
Numeric |
Float64 |
||
hash_count |
Unary |
Any |
Int64 |
(2) |
|
hash_count_all |
Nullary |
Int64 |
|||
hash_count_distinct |
Unary |
Any |
Int64 |
(2) |
|
hash_distinct |
Unary |
Any |
List of input type |
(2) (3) |
|
hash_first |
Unary |
Numeric, Binary |
Input type |
(10) |
|
hash_first_last |
Unary |
Numeric, Binary |
Struct |
(10) |
|
hash_last |
Unary |
Numeric, Binary |
Input type |
(10) |
|
hash_list |
Unary |
Any |
List of input type |
(3) |
|
hash_max |
Unary |
Non-nested, non-binary/string-like |
Input type |
||
hash_mean |
Unary |
Numeric |
Decimal/Float64 |
(4) |
|
hash_min |
Unary |
Non-nested, non-binary/string-like |
Input type |
||
hash_min_max |
Unary |
Non-nested types |
Struct |
(5) |
|
hash_one |
Unary |
Any |
Input type |
(6) |
|
hash_product |
Unary |
Numeric |
Numeric |
(7) |
|
hash_stddev |
Unary |
Numeric |
Float64 |
(8) |
|
hash_sum |
Unary |
Numeric |
Numeric |
(7) |
|
hash_tdigest |
Unary |
Numeric |
FixedSizeList[Float64] |
(9) |
|
hash_variance |
Unary |
Numeric |
Float64 |
(8) |
(1) If null values are taken into account, by setting the
ScalarAggregateOptions::skip_nulls
to false, then Kleene logic logic is applied. The min_count option is not respected.(2) CountMode controls whether only non-null values are counted (the default), only null values are counted, or all values are counted. For hash_distinct, it instead controls whether null values are emitted. This never affects the grouping keys, only group values (i.e. you may get a group where the key is null).
(3)
hash_distinct
andhash_list
gather the grouped values into a list array.(4) For decimal inputs, the resulting decimal will have the same precision and scale. The result is rounded away from zero.
(5) Output is a
{"min": input type, "max": input type}
Struct array.Of the interval types, only the month interval is supported, as the day-time and month-day-nano types are not sortable.
(6)
hash_one
returns one arbitrary value from the input for each group. The function is biased towards non-null values: if there is at least one non-null value for a certain group, that value is returned, and only if all the values arenull
for the group will the function returnnull
.(7) Output is Int64, UInt64, Float64, or Decimal128/256, depending on the input type.
(8) Decimal arguments are cast to Float64 first.
(9) T-digest computes approximate quantiles, and so only needs a fixed amount of memory. See the reference implementation for details.
(10) Result is based on ordering of the input data.
Decimal arguments are cast to Float64 first.
Element-wise (“scalar”) functions#
All element-wise functions accept both arrays and scalars as input. The semantics for unary functions are as follow:
scalar inputs produce a scalar output
array inputs produce an array output
Binary functions have the following semantics (which is sometimes called “broadcasting” in other systems such as NumPy):
(scalar, scalar)
inputs produce a scalar output(array, array)
inputs produce an array output (and both inputs must be of the same length)(scalar, array)
and(array, scalar)
produce an array output. The scalar input is handled as if it were an array of the same length N as the other input, with the same value repeated N times.
Arithmetic functions#
These functions expect inputs of numeric type and apply a given arithmetic operation to each element(s) gathered from the input(s). If any of the input element(s) is null, the corresponding output element is null. For binary functions, input(s) will be cast to the common numeric type (and dictionary decoded, if applicable) before the operation is applied.
The default variant of these functions does not detect overflow (the result
then typically wraps around). Most functions are also available in an
overflow-checking variant, suffixed _checked
, which returns
an Invalid
Status
when overflow is detected.
For functions which support decimal inputs (currently add
, subtract
,
multiply
, and divide
and their checked variants), decimals of different
precisions/scales will be promoted appropriately. Mixed decimal and
floating-point arguments will cast all arguments to floating-point, while mixed
decimal and integer arguments will cast all arguments to decimals.
Mixed time resolution temporal inputs will be cast to finest input resolution.
Function name |
Arity |
Input types |
Output type |
Notes |
---|---|---|---|---|
abs |
Unary |
Numeric/Duration |
Numeric/Duration |
|
abs_checked |
Unary |
Numeric/Duration |
Numeric/Duration |
|
add |
Binary |
Numeric/Temporal |
Numeric/Temporal |
(1) |
add_checked |
Binary |
Numeric/Temporal |
Numeric/Temporal |
(1) |
divide |
Binary |
Numeric/Temporal |
Numeric/Temporal |
(1) |
divide_checked |
Binary |
Numeric/Temporal |
Numeric/Temporal |
(1) |
exp |
Unary |
Numeric |
Float32/Float64 |
|
expm1 |
Unary |
Numeric |
Float32/Float64 |
|
multiply |
Binary |
Numeric/Temporal |
Numeric/Temporal |
(1) |
multiply_checked |
Binary |
Numeric/Temporal |
Numeric/Temporal |
(1) |
negate |
Unary |
Numeric/Duration |
Numeric/Duration |
|
negate_checked |
Unary |
Signed Numeric/Duration |
Signed Numeric/Duration |
|
power |
Binary |
Numeric |
Numeric |
|
power_checked |
Binary |
Numeric |
Numeric |
|
sign |
Unary |
Numeric/Duration |
Int8/Float32/Float64 |
(2) |
sqrt |
Unary |
Numeric |
Numeric |
|
sqrt_checked |
Unary |
Numeric |
Numeric |
|
subtract |
Binary |
Numeric/Temporal |
Numeric/Temporal |
(1) |
subtract_checked |
Binary |
Numeric/Temporal |
Numeric/Temporal |
(1) |
(1) Precision and scale of computed DECIMAL results
Operation
Result precision and scale
addsubtractscale = max(s1, s2)precision = max(p1-s1, p2-s2) + 1 + scalemultiply
scale = s1 + s2precision = p1 + p2 + 1divide
scale = max(4, s1 + p2 - s2 + 1)precision = p1 - s1 + s2 + scaleIt’s compatible with Redshift’s decimal promotion rules. All decimal digits are preserved for
add
,subtract
andmultiply
operations. The result precision ofdivide
is at least the sum of precisions of both operands with enough scale kept. Error is returned if the result precision is beyond the decimal value range.(2) Output is any of (-1,1) for nonzero inputs and 0 for zero input. NaN values return NaN. Integral and decimal values return signedness as Int8 and floating-point values return it with the same type as the input values.
Bit-wise functions#
Function name |
Arity |
Input types |
Output type |
---|---|---|---|
bit_wise_and |
Binary |
Numeric |
Numeric |
bit_wise_not |
Unary |
Numeric |
Numeric |
bit_wise_or |
Binary |
Numeric |
Numeric |
bit_wise_xor |
Binary |
Numeric |
Numeric |
shift_left |
Binary |
Numeric |
Numeric |
shift_left_checked |
Binary |
Numeric |
Numeric (1) |
shift_right |
Binary |
Numeric |
Numeric |
shift_right_checked |
Binary |
Numeric |
Numeric (1) |
(1) An error is emitted if the shift amount (i.e. the second input) is out of bounds for the data type. However, an overflow when shifting the first input is not error (truncated bits are silently discarded).
Rounding functions#
Rounding functions displace numeric inputs to an approximate value with a simpler representation based on the rounding criterion.
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
ceil |
Unary |
Numeric |
Float32/Float64/Decimal |
||
floor |
Unary |
Numeric |
Float32/Float64/Decimal |
||
round |
Unary |
Numeric |
Input Type |
(1)(2) |
|
round_to_multiple |
Unary |
Numeric |
Input Type |
(1)(3) |
|
round_binary |
Binary |
Numeric |
Input Type |
(1)(4) |
|
trunc |
Unary |
Numeric |
Float32/Float64/Decimal |
(1) By default rounding functions change a value to the nearest integer using HALF_TO_EVEN to resolve ties. Options are available to control the rounding criterion. All
round
functions have theround_mode
option to set the rounding mode.(2) Round to a number of digits where the
ndigits
option ofRoundOptions
specifies the rounding precision in terms of number of digits. A negative value corresponds to digits in the non-fractional part. For example, -2 corresponds to rounding to the nearest multiple of 100 (zeroing the ones and tens digits). Default value ofndigits
is 0 which rounds to the nearest integer. For integer inputs a non-negativendigits
value is ignored and the input is returned unchanged. For integer inputs, if-ndigits
is larger than the maximum number of digits the input type can hold, an error is returned.(3) Round to a multiple where the
multiple
option ofRoundToMultipleOptions
specifies the rounding scale. The rounding multiple has to be a positive value and can be casted to input type. For example, 100 corresponds to rounding to the nearest multiple of 100 (zeroing the ones and tens digits). Default value ofmultiple
is 1 which rounds to the nearest integer.(4) Round the first input to multiple of the second input. The rounding multiple has to be a positive value and can be casted to the first input type. For example, 100 corresponds to rounding to the nearest multiple of 100 (zeroing the ones and tens digits).
For round
functions, the following rounding modes are available.
Tie-breaking modes are prefixed with HALF and round non-ties to the nearest integer.
The example values are given for default values of ndigits
and multiple
.
|
Operation performed |
Example values |
---|---|---|
DOWN |
Round to nearest integer less than or equal in magnitude;
also known as |
3.2 -> 3, 3.7 -> 3, -3.2 -> -4, -3.7 -> -4 |
UP |
Round to nearest integer greater than or equal in magnitude;
also known as |
3.2 -> 4, 3.7 -> 4, -3.2 -> -3, -3.7 -> -3 |
TOWARDS_ZERO |
Get the integral part without fractional digits;
also known as |
3.2 -> 3, 3.7 -> 3, -3.2 -> -3, -3.7 -> -3 |
TOWARDS_INFINITY |
Round negative values with |
3.2 -> 4, 3.7 -> 4, -3.2 -> -4, -3.7 -> -4 |
HALF_DOWN |
Round ties with |
3.5 -> 3, 4.5 -> 4, -3.5 -> -4, -4.5 -> -5 |
HALF_UP |
Round ties with |
3.5 -> 4, 4.5 -> 5, -3.5 -> -3, -4.5 -> -4 |
HALF_TOWARDS_ZERO |
Round ties with |
3.5 -> 3, 4.5 -> 4, -3.5 -> -3, -4.5 -> -4 |
HALF_TOWARDS_INFINITY |
Round ties with |
3.5 -> 4, 4.5 -> 5, -3.5 -> -4, -4.5 -> -5 |
HALF_TO_EVEN |
Round ties to nearest even integer |
3.5 -> 4, 4.5 -> 4, -3.5 -> -4, -4.5 -> -4 |
HALF_TO_ODD |
Round ties to nearest odd integer |
3.5 -> 3, 4.5 -> 5, -3.5 -> -3, -4.5 -> -5 |
The following table gives examples of how ndigits
(for the round
and round_binary
functions) and multiple
(for round_to_multiple
)
influence the operation performed, respectively.
Round |
Round |
Operation performed |
---|---|---|
1 |
0 |
Round to integer |
0.001 |
3 |
Round to 3 decimal places |
10 |
-1 |
Round to multiple of 10 |
2 |
NA |
Round to multiple of 2 |
Logarithmic functions#
Logarithmic functions are also supported, and also offer _checked
variants that check for domain errors if needed.
Decimal values are accepted, but are cast to Float64 first.
Function name |
Arity |
Input types |
Output type |
---|---|---|---|
ln |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
ln_checked |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
log10 |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
log10_checked |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
log1p |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
log1p_checked |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
log2 |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
log2_checked |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
logb |
Binary |
Float32/Float64/Decimal |
Float32/Float64 |
logb_checked |
Binary |
Float32/Float64/Decimal |
Float32/Float64 |
Trigonometric functions#
Trigonometric functions are also supported, and also offer _checked
variants that check for domain errors if needed.
Decimal values are accepted, but are cast to Float64 first.
Function name |
Arity |
Input types |
Output type |
---|---|---|---|
acos |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
acos_checked |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
asin |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
asin_checked |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
atan |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
atan2 |
Binary |
Float32/Float64/Decimal |
Float32/Float64 |
cos |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
cos_checked |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
sin |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
sin_checked |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
tan |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
tan_checked |
Unary |
Float32/Float64/Decimal |
Float32/Float64 |
Comparisons#
These functions expect two inputs of numeric type (in which case they will be
cast to the common numeric type before comparison),
or two inputs of Binary- or String-like types, or two inputs of Temporal types.
If any input is dictionary encoded it will be expanded for the purposes of
comparison. If any of the input elements in a pair is null, the corresponding
output element is null. Decimal arguments will be promoted in the same way as
for add
and subtract
.
Function names |
Arity |
Input types |
Output type |
---|---|---|---|
equal |
Binary |
Numeric, Temporal, Binary- and String-like |
Boolean |
greater |
Binary |
Numeric, Temporal, Binary- and String-like |
Boolean |
greater_equal |
Binary |
Numeric, Temporal, Binary- and String-like |
Boolean |
less |
Binary |
Numeric, Temporal, Binary- and String-like |
Boolean |
less_equal |
Binary |
Numeric, Temporal, Binary- and String-like |
Boolean |
not_equal |
Binary |
Numeric, Temporal, Binary- and String-like |
Boolean |
These functions take any number of inputs of numeric type (in which case they will be cast to the common numeric type before comparison) or of temporal types. If any input is dictionary encoded it will be expanded for the purposes of comparison.
Function names |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
max_element_wise |
Varargs |
Numeric, Temporal, Binary- and String-like |
Numeric or Temporal |
(1) |
|
min_element_wise |
Varargs |
Numeric, Temporal, Binary- and String-like |
Numeric or Temporal |
(1) |
(1) By default, nulls are skipped (but the kernel can be configured to propagate nulls). For floating point values, NaN will be taken over null but not over any other value. For binary- and string-like values, only identical type parameters are supported.
Logical functions#
The normal behaviour for these functions is to emit a null if any of the
inputs is null (similar to the semantics of NaN
in floating-point
computations).
Some of them are also available in a Kleene logic variant (suffixed
_kleene
) where null is taken to mean “undefined”. This is the
interpretation of null used in SQL systems as well as R and Julia,
for example.
For the Kleene logic variants, therefore:
“true AND null”, “null AND true” give “null” (the result is undefined)
“true OR null”, “null OR true” give “true”
“false AND null”, “null AND false” give “false”
“false OR null”, “null OR false” give “null” (the result is undefined)
Function name |
Arity |
Input types |
Output type |
---|---|---|---|
and |
Binary |
Boolean |
Boolean |
and_kleene |
Binary |
Boolean |
Boolean |
and_not |
Binary |
Boolean |
Boolean |
and_not_kleene |
Binary |
Boolean |
Boolean |
invert |
Unary |
Boolean |
Boolean |
or |
Binary |
Boolean |
Boolean |
or_kleene |
Binary |
Boolean |
Boolean |
xor |
Binary |
Boolean |
Boolean |
String predicates#
These functions classify the input string elements according to their character
contents. An empty string element emits false in the output. For ASCII
variants of the functions (prefixed ascii_
), a string element with non-ASCII
characters emits false in the output.
The first set of functions operates on a character-per-character basis, and emit true in the output if the input contains only characters of a given class:
Function name |
Arity |
Input types |
Output type |
Matched character class |
Notes |
---|---|---|---|---|---|
ascii_is_alnum |
Unary |
String-like |
Boolean |
Alphanumeric ASCII |
|
ascii_is_alpha |
Unary |
String-like |
Boolean |
Alphabetic ASCII |
|
ascii_is_decimal |
Unary |
String-like |
Boolean |
Decimal ASCII |
(1) |
ascii_is_lower |
Unary |
String-like |
Boolean |
Lowercase ASCII |
(2) |
ascii_is_printable |
Unary |
String-like |
Boolean |
Printable ASCII |
|
ascii_is_space |
Unary |
String-like |
Boolean |
Whitespace ASCII |
|
ascii_is_upper |
Unary |
String-like |
Boolean |
Uppercase ASCII |
(2) |
utf8_is_alnum |
Unary |
String-like |
Boolean |
Alphanumeric Unicode |
|
utf8_is_alpha |
Unary |
String-like |
Boolean |
Alphabetic Unicode |
|
utf8_is_decimal |
Unary |
String-like |
Boolean |
Decimal Unicode |
|
utf8_is_digit |
Unary |
String-like |
Boolean |
Unicode digit |
(3) |
utf8_is_lower |
Unary |
String-like |
Boolean |
Lowercase Unicode |
(2) |
utf8_is_numeric |
Unary |
String-like |
Boolean |
Numeric Unicode |
(4) |
utf8_is_printable |
Unary |
String-like |
Boolean |
Printable Unicode |
|
utf8_is_space |
Unary |
String-like |
Boolean |
Whitespace Unicode |
|
utf8_is_upper |
Unary |
String-like |
Boolean |
Uppercase Unicode |
(2) |
(1) Also matches all numeric ASCII characters and all ASCII digits.
(2) Non-cased characters, such as punctuation, do not match.
(3) This is currently the same as
utf8_is_decimal
.(4) Unlike
utf8_is_decimal
, non-decimal numeric characters also match.
The second set of functions also consider the character order in a string element:
Function name |
Arity |
Input types |
Output type |
Notes |
---|---|---|---|---|
ascii_is_title |
Unary |
String-like |
Boolean |
(1) |
utf8_is_title |
Unary |
String-like |
Boolean |
(1) |
(1) Output is true iff the input string element is title-cased, i.e. any word starts with an uppercase character, followed by lowercase characters. Word boundaries are defined by non-cased characters.
The third set of functions examines string elements on a byte-per-byte basis:
Function name |
Arity |
Input types |
Output type |
Notes |
---|---|---|---|---|
string_is_ascii |
Unary |
String-like |
Boolean |
(1) |
(1) Output is true iff the input string element contains only ASCII characters, i.e. only bytes in [0, 127].
String transforms#
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
ascii_capitalize |
Unary |
String-like |
String-like |
(1) |
|
ascii_lower |
Unary |
String-like |
String-like |
(1) |
|
ascii_reverse |
Unary |
String-like |
String-like |
(2) |
|
ascii_swapcase |
Unary |
String-like |
String-like |
(1) |
|
ascii_title |
Unary |
String-like |
String-like |
(1) |
|
ascii_upper |
Unary |
String-like |
String-like |
(1) |
|
binary_length |
Unary |
Binary- or String-like |
Int32 or Int64 |
(3) |
|
binary_repeat |
Binary |
Binary/String (Arg 0); Integral (Arg 1) |
Binary- or String-like |
(4) |
|
binary_replace_slice |
Unary |
String-like |
Binary- or String-like |
(5) |
|
binary_reverse |
Unary |
Binary |
Binary |
(6) |
|
replace_substring |
Unary |
String-like |
String-like |
(7) |
|
replace_substring_regex |
Unary |
String-like |
String-like |
(8) |
|
utf8_capitalize |
Unary |
String-like |
String-like |
(9) |
|
utf8_length |
Unary |
String-like |
Int32 or Int64 |
(10) |
|
utf8_lower |
Unary |
String-like |
String-like |
(9) |
|
utf8_replace_slice |
Unary |
String-like |
String-like |
(7) |
|
utf8_reverse |
Unary |
String-like |
String-like |
(11) |
|
utf8_swapcase |
Unary |
String-like |
String-like |
(9) |
|
utf8_title |
Unary |
String-like |
String-like |
(9) |
|
utf8_upper |
Unary |
String-like |
String-like |
(9) |
(1) Each ASCII character in the input is converted to lowercase or uppercase. Non-ASCII characters are left untouched.
(2) ASCII input is reversed to the output. If non-ASCII characters are present,
Invalid
Status
will be returned.(3) Output is the physical length in bytes of each input element. Output type is Int32 for Binary/String, Int64 for LargeBinary/LargeString.
(4) Repeat the input binary string a given number of times.
(5) Replace the slice of the substring from
ReplaceSliceOptions::start
(inclusive) toReplaceSliceOptions::stop
(exclusive) byReplaceSubstringOptions::replacement
. The binary kernel measures the slice in bytes, while the UTF8 kernel measures the slice in codeunits.(6) Perform a byte-level reverse.
(7) Replace non-overlapping substrings that match to
ReplaceSubstringOptions::pattern
byReplaceSubstringOptions::replacement
. IfReplaceSubstringOptions::max_replacements
!= -1, it determines the maximum number of replacements made, counting from the left.(8) Replace non-overlapping substrings that match to the regular expression
ReplaceSubstringOptions::pattern
byReplaceSubstringOptions::replacement
, using the Google RE2 library. IfReplaceSubstringOptions::max_replacements
!= -1, it determines the maximum number of replacements made, counting from the left. Note that if the pattern contains groups, backreferencing can be used.(9) Each UTF8-encoded character in the input is converted to lowercase or uppercase.
(10) Output is the number of characters (not bytes) of each input element. Output type is Int32 for String, Int64 for LargeString.
(11) Each UTF8-encoded code unit is written in reverse order to the output. If the input is not valid UTF8, then the output is undefined (but the size of output buffers will be preserved).
String padding#
These functions append/prepend a given padding byte (ASCII) or codepoint (UTF8) in order to center (center), right-align (lpad), or left-align (rpad) a string.
Function name |
Arity |
Input types |
Output type |
Options class |
---|---|---|---|---|
ascii_center |
Unary |
String-like |
String-like |
|
ascii_lpad |
Unary |
String-like |
String-like |
|
ascii_rpad |
Unary |
String-like |
String-like |
|
utf8_center |
Unary |
String-like |
String-like |
|
utf8_lpad |
Unary |
String-like |
String-like |
|
utf8_rpad |
Unary |
String-like |
String-like |
String trimming#
These functions trim off characters on both sides (trim), or the left (ltrim) or right side (rtrim).
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
ascii_ltrim |
Unary |
String-like |
String-like |
(1) |
|
ascii_ltrim_whitespace |
Unary |
String-like |
String-like |
(2) |
|
ascii_rtrim |
Unary |
String-like |
String-like |
(1) |
|
ascii_rtrim_whitespace |
Unary |
String-like |
String-like |
(2) |
|
ascii_trim |
Unary |
String-like |
String-like |
(1) |
|
ascii_trim_whitespace |
Unary |
String-like |
String-like |
(2) |
|
utf8_ltrim |
Unary |
String-like |
String-like |
(3) |
|
utf8_ltrim_whitespace |
Unary |
String-like |
String-like |
(4) |
|
utf8_rtrim |
Unary |
String-like |
String-like |
(3) |
|
utf8_rtrim_whitespace |
Unary |
String-like |
String-like |
(4) |
|
utf8_trim |
Unary |
String-like |
String-like |
(3) |
|
utf8_trim_whitespace |
Unary |
String-like |
String-like |
(4) |
(1) Only characters specified in
TrimOptions::characters
will be trimmed off. Both the input string and thecharacters
argument are interpreted as ASCII characters.(2) Only trim off ASCII whitespace characters (
'\t'
,'\n'
,'\v'
,'\f'
,'\r'
and' '
).(3) Only characters specified in
TrimOptions::characters
will be trimmed off.(4) Only trim off Unicode whitespace characters.
String splitting#
These functions split strings into lists of strings. All kernels can optionally
be configured with a max_splits
and a reverse
parameter, where
max_splits == -1
means no limit (the default). When reverse
is true,
the splitting is done starting from the end of the string; this is only relevant
when a positive max_splits
is given.
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
ascii_split_whitespace |
Unary |
String-like |
List-like |
(1) |
|
split_pattern |
Unary |
Binary- or String-like |
List-like |
(2) |
|
split_pattern_regex |
Unary |
Binary- or String-like |
List-like |
(3) |
|
utf8_split_whitespace |
Unary |
String-like |
List-like |
(4) |
(1) A non-zero length sequence of ASCII defined whitespace bytes (
'\t'
,'\n'
,'\v'
,'\f'
,'\r'
and' '
) is seen as separator.(2) The string is split when an exact pattern is found (the pattern itself is not included in the output).
(3) The string is split when a regex match is found (the matched substring itself is not included in the output).
(4) A non-zero length sequence of Unicode defined whitespace codepoints is seen as separator.
String component extraction#
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
extract_regex |
Unary |
Binary- or String-like |
Struct |
(1) |
(1) Extract substrings defined by a regular expression using the Google RE2 library. The output struct field names refer to the named capture groups, e.g. ‘letter’ and ‘digit’ for the regular expression
(?P<letter>[ab])(?P<digit>\\d)
.
String joining#
These functions do the inverse of string splitting.
Function name |
Arity |
Input type 1 |
Input type 2 |
Output type |
Options class |
Notes |
---|---|---|---|---|---|---|
binary_join |
Binary |
List of Binary- or String-like |
String-like |
String-like |
(1) |
|
binary_join_element_wise |
Varargs |
Binary- or String-like (varargs) |
Binary- or String-like |
Binary- or String-like |
(2) |
(1) The first input must be an array, while the second can be a scalar or array. Each list of values in the first input is joined using each second input as separator. If any input list is null or contains a null, the corresponding output will be null.
(2) All arguments are concatenated element-wise, with the last argument treated as the separator (scalars are recycled in either case). Null separators emit null. If any other argument is null, by default the corresponding output will be null, but it can instead either be skipped or replaced with a given string.
String Slicing#
This function transforms each sequence of the array to a subsequence, according to start and stop indices, and a non-zero step (defaulting to 1). Slicing semantics follow Python slicing semantics: the start index is inclusive, the stop index exclusive; if the step is negative, the sequence is followed in reverse order.
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
binary_slice |
Unary |
Binary-like |
Binary-like |
(1) |
|
utf8_slice_codeunits |
Unary |
String-like |
String-like |
(2) |
(1) Slice string into a substring defined by (
start
,stop
,step
) as given bySliceOptions
wherestart
andstop
are measured in bytes. Null inputs emit null.(2) Slice string into a substring defined by (
start
,stop
,step
) as given bySliceOptions
wherestart
andstop
are measured in codeunits. Null inputs emit null.
Containment tests#
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
count_substring |
Unary |
Binary- or String-like |
Int32 or Int64 |
(1) |
|
count_substring_regex |
Unary |
Binary- or String-like |
Int32 or Int64 |
(1) |
|
ends_with |
Unary |
Binary- or String-like |
Boolean |
(2) |
|
find_substring |
Unary |
Binary- and String-like |
Int32 or Int64 |
(3) |
|
find_substring_regex |
Unary |
Binary- and String-like |
Int32 or Int64 |
(3) |
|
index_in |
Unary |
Boolean, Null, Numeric, Temporal, Binary- and String-like |
Int32 |
(4) |
|
is_in |
Unary |
Boolean, Null, Numeric, Temporal, Binary- and String-like |
Boolean |
(5) |
|
match_like |
Unary |
Binary- or String-like |
Boolean |
(6) |
|
match_substring |
Unary |
Binary- or String-like |
Boolean |
(7) |
|
match_substring_regex |
Unary |
Binary- or String-like |
Boolean |
(8) |
|
starts_with |
Unary |
Binary- or String-like |
Boolean |
(2) |
(1) Output is the number of occurrences of
MatchSubstringOptions::pattern
in the corresponding input string. Output type is Int32 for Binary/String, Int64 for LargeBinary/LargeString.(2) Output is true iff
MatchSubstringOptions::pattern
is a suffix/prefix of the corresponding input.(3) Output is the index of the first occurrence of
MatchSubstringOptions::pattern
in the corresponding input string, otherwise -1. Output type is Int32 for Binary/String, Int64 for LargeBinary/LargeString.(4) Output is the index of the corresponding input element in
SetLookupOptions::value_set
, if found there. Otherwise, output is null.(5) Output is true iff the corresponding input element is equal to one of the elements in
SetLookupOptions::value_set
.(6) Output is true iff the SQL-style LIKE pattern
MatchSubstringOptions::pattern
fully matches the corresponding input element. That is,%
will match any number of characters,_
will match exactly one character, and any other character matches itself. To match a literal percent sign or underscore, precede the character with a backslash.(7) Output is true iff
MatchSubstringOptions::pattern
is a substring of the corresponding input element.(8) Output is true iff
MatchSubstringOptions::pattern
matches the corresponding input element at any position.
Categorizations#
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
is_finite |
Unary |
Null, Numeric |
Boolean |
(1) |
|
is_inf |
Unary |
Null, Numeric |
Boolean |
(2) |
|
is_nan |
Unary |
Null, Numeric |
Boolean |
(3) |
|
is_null |
Unary |
Any |
Boolean |
(4) |
|
is_valid |
Unary |
Any |
Boolean |
(5) |
|
true_unless_null |
Unary |
Any |
Boolean |
(6) |
(1) Output is true iff the corresponding input element is finite (neither Infinity, -Infinity, nor NaN). Hence, for Decimal and integer inputs this always returns true.
(2) Output is true iff the corresponding input element is Infinity/-Infinity. Hence, for Decimal and integer inputs this always returns false.
(3) Output is true iff the corresponding input element is NaN. Hence, for Decimal and integer inputs this always returns false.
(4) Output is true iff the corresponding input element is null. NaN values can also be considered null by setting
NullOptions::nan_is_null
.(5) Output is true iff the corresponding input element is non-null, else false.
- (6) Output is true iff the corresponding input element is non-null, else null.
Mostly intended for expression simplification/guarantees.
Selecting / multiplexing#
For each “row” of input values, these functions emit one of the input values, depending on a condition.
Function name |
Arity |
Input types |
Output type |
Notes |
---|---|---|---|---|
case_when |
Varargs |
Struct of Boolean (Arg 0), Any (rest) |
Input type |
(1) |
choose |
Varargs |
Integral (Arg 0), Fixed-width/Binary-like (rest) |
Input type |
(2) |
coalesce |
Varargs |
Any |
Input type |
(3) |
if_else |
Ternary |
Boolean (Arg 0), Any (rest) |
Input type |
(4) |
(1) This function acts like a SQL “case when” statement or switch-case. The input is a “condition” value, which is a struct of Booleans, followed by the values for each “branch”. There must be either exactly one value argument for each child of the condition struct, or one more value argument than children (in which case we have an “else” or “default” value). The output is of the same type as the value inputs; each row will be the corresponding value from the first value datum for which the corresponding Boolean is true, or the corresponding value from the “default” input, or null otherwise.
Note that currently, while all types are supported, dictionaries will be unpacked.
(2) The first input must be an integral type. The rest of the arguments can be any type, but must all be the same type or promotable to a common type. Each value of the first input (the ‘index’) is used as a zero-based index into the remaining arguments (i.e. index 0 is the second argument, index 1 is the third argument, etc.), and the value of the output for that row will be the corresponding value of the selected input at that row. If the index is null, then the output will also be null.
(3) Each row of the output will be the corresponding value of the first input which is non-null for that row, otherwise null.
(4) First input must be a Boolean scalar or array. Second and third inputs could be scalars or arrays and must be of the same type. Output is an array (or scalar if all inputs are scalar) of the same type as the second/ third input. If the nulls present on the first input, they will be promoted to the output, otherwise nulls will be chosen based on the first input values.
Also see: replace_with_mask.
Structural transforms#
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
list_value_length |
Unary |
List-like |
Int32 or Int64 |
(1) |
|
make_struct |
Varargs |
Any |
Struct |
(2) |
(1) Each output element is the length of the corresponding input element (null if input is null). Output type is Int32 for List, ListView, and FixedSizeList, Int64 for LargeList and LargeListView.
(2) The output struct’s field types are the types of its arguments. The field names are specified using an instance of
MakeStructOptions
. The output shape will be scalar if all inputs are scalar, otherwise any scalars will be broadcast to arrays.
Conversions#
A general conversion function named cast
is provided which accepts a large
number of input and output types. The type to cast to can be passed in a
CastOptions
instance. As an alternative, the same service is
provided by a concrete function Cast()
.
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
ceil_temporal |
Unary |
Temporal |
Temporal |
||
floor_temporal |
Unary |
Temporal |
Temporal |
||
round_temporal |
Unary |
Temporal |
Temporal |
||
cast |
Unary |
Many |
Variable |
||
strftime |
Unary |
Temporal |
String |
(1) |
|
strptime |
Unary |
String-like |
Timestamp |
The conversions available with cast
are listed below. In all cases, a
null input value is converted into a null output value.
(1) Output precision of
%S
(seconds) flag depends on the input timestamp precision. Timestamps with second precision are represented as integers while milliseconds, microsecond and nanoseconds are represented as fixed floating point numbers with 3, 6 and 9 decimal places respectively. To obtain integer seconds, cast to timestamp with second resolution. The character for the decimal point is localized according to the locale. See detailed formatting documentation for descriptions of other flags.
Truth value extraction
Input type |
Output type |
Notes |
---|---|---|
Binary- and String-like |
Boolean |
(1) |
Numeric |
Boolean |
(2) |
(1) Output is true iff the corresponding input value has non-zero length.
(2) Output is true iff the corresponding input value is non-zero.
Same-kind conversion
Input type |
Output type |
Notes |
---|---|---|
Int32 |
32-bit Temporal |
(1) |
Int64 |
64-bit Temporal |
(1) |
(Large)Binary |
(Large)String |
(2) |
(Large)String |
(Large)Binary |
(3) |
Numeric |
Numeric |
(4) (5) |
32-bit Temporal |
Int32 |
(1) |
64-bit Temporal |
Int64 |
(1) |
Temporal |
Temporal |
(4) (5) |
(1) No-operation cast: the raw values are kept identical, only the type is changed.
(2) Validates the contents if
CastOptions::allow_invalid_utf8
is false.(3) No-operation cast: only the type is changed.
(4) Overflow and truncation checks are enabled depending on the given
CastOptions
.(5) Not all such casts have been implemented.
String representations
Input type |
Output type |
Notes |
---|---|---|
Boolean |
String-like |
|
Numeric |
String-like |
Generic conversions
Input type |
Output type |
Notes |
---|---|---|
Dictionary |
Dictionary value type |
(1) |
Extension |
Extension storage type |
|
Struct |
Struct |
(2) |
List-like |
List-like or (Large)ListView |
(3) |
(Large)ListView |
List-like or (Large)ListView |
(4) |
Map |
Map or List of two-field struct |
(5) |
Null |
Any |
|
Any |
Extension |
(6) |
(1) The dictionary indices are unchanged, the dictionary values are cast from the input value type to the output value type (if a conversion is available).
(2) The field names of the output type must be the same or a subset of the field names of the input type; they also must have the same order. Casting to a subset of field names “selects” those fields such that each output field matches the data of the input field with the same name.
(3) The list offsets are unchanged, the list values are cast from the input value type to the output value type (if a conversion is available). If the output type is (Large)ListView, then sizes are derived from the offsets.
(4) If output type is list-like, offsets (consequently, the values array) might have to be rebuilt to be sorted and spaced adequately. If output type is a list-view type, the offsets and sizes are unchanged. In any case, the list values are cast from the input value type to the output value type (if a conversion is available).
(5) Offsets are unchanged, the keys and values are cast from respective input to output types (if a conversion is available). If output type is a list of struct, the key field is output as the first field and the value field the second field, regardless of field names chosen.
(6) Any input type that can be cast to the resulting extension’s storage type. This excludes extension types, unless being cast to the same extension type.
Temporal component extraction#
These functions extract datetime components (year, month, day, etc) from temporal types. For timestamps inputs with non-empty timezone, localized timestamp components will be returned.
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
day |
Unary |
Temporal |
Int64 |
||
day_of_week |
Unary |
Temporal |
Int64 |
(1) |
|
day_of_year |
Unary |
Temporal |
Int64 |
||
hour |
Unary |
Timestamp, Time |
Int64 |
||
is_dst |
Unary |
Timestamp |
Boolean |
||
iso_week |
Unary |
Temporal |
Int64 |
(2) |
|
iso_year |
Unary |
Temporal |
Int64 |
(2) |
|
iso_calendar |
Unary |
Temporal |
Struct |
(3) |
|
is_leap_year |
Unary |
Timestamp, Date |
Boolean |
||
microsecond |
Unary |
Timestamp, Time |
Int64 |
||
millisecond |
Unary |
Timestamp, Time |
Int64 |
||
minute |
Unary |
Timestamp, Time |
Int64 |
||
month |
Unary |
Temporal |
Int64 |
||
nanosecond |
Unary |
Timestamp, Time |
Int64 |
||
quarter |
Unary |
Temporal |
Int64 |
||
second |
Unary |
Timestamp, Time |
Int64 |
||
subsecond |
Unary |
Timestamp, Time |
Float64 |
||
us_week |
Unary |
Temporal |
Int64 |
(4) |
|
us_year |
Unary |
Temporal |
Int64 |
(4) |
|
week |
Unary |
Timestamp |
Int64 |
(5) |
|
year |
Unary |
Temporal |
Int64 |
||
year_month_day |
Unary |
Temporal |
Struct |
(6) |
(1) Outputs the number of the day of the week. By default week begins on Monday represented by 0 and ends on Sunday represented by 6. Day numbering can start with 0 or 1 based on
DayOfWeekOptions::count_from_zero
parameter.DayOfWeekOptions::week_start
can be used to set the starting day of the week using ISO convention (Monday=1, Sunday=7).DayOfWeekOptions::week_start
parameter is not affected byDayOfWeekOptions::count_from_zero
.(2) First ISO week has the majority (4 or more) of it’s days in January. ISO year starts with the first ISO week. ISO week starts on Monday. See ISO 8601 week date definition for more details.
(3) Output is a
{"iso_year": output type, "iso_week": output type, "iso_day_of_week": output type}
Struct.(4) First US week has the majority (4 or more) of its days in January. US year starts with the first US week. US week starts on Sunday.
(5) Returns week number allowing for setting several parameters. If
WeekOptions::week_starts_monday
is true, the week starts with Monday, else Sunday if false. IfWeekOptions::count_from_zero
is true, dates from the current year that fall into the last ISO week of the previous year are numbered as week 0, else week 52 or 53 if false. IfWeekOptions::first_week_is_fully_in_year
is true, the first week (week 1) must fully be in January; else if false, a week that begins on December 29, 30, or 31 is considered the first week of the new year.(6) Output is a
{"year": int64(), "month": int64(), "day": int64()}
Struct.
Temporal difference#
These functions compute the difference between two timestamps in the specified unit. The difference is determined by the number of boundaries crossed, not the span of time. For example, the difference in days between 23:59:59 on one day and 00:00:01 on the next day is one day (since midnight was crossed), not zero days (even though less than 24 hours elapsed). Additionally, if the timestamp has a defined timezone, the difference is calculated in the local timezone. For instance, the difference in years between “2019-12-31 18:00:00-0500” and “2019-12-31 23:00:00-0500” is zero years, because the local year is the same, even though the UTC years would be different.
Function name |
Arity |
Input types |
Output type |
Options class |
---|---|---|---|---|
day_time_interval_between |
Binary |
Temporal |
DayTime interval |
|
days_between |
Binary |
Timestamp, Date |
Int64 |
|
hours_between |
Binary |
Temporal |
Int64 |
|
microseconds_between |
Binary |
Temporal |
Int64 |
|
milliseconds_between |
Binary |
Temporal |
Int64 |
|
minutes_between |
Binary |
Temporal |
Int64 |
|
month_day_nano_interval_between |
Binary |
Temporal |
MonthDayNano interval |
|
month_interval_between |
Binary |
Timestamp, Date |
Month interval |
|
nanoseconds_between |
Binary |
Temporal |
Int64 |
|
quarters_between |
Binary |
Timestamp, Date |
Int64 |
|
seconds_between |
Binary |
Temporal |
Int64 |
|
weeks_between |
Binary |
Timestamp, Date |
Int64 |
|
years_between |
Binary |
Timestamp, Date |
Int64 |
Timezone handling#
assume_timezone
function is meant to be used when an external system produces
“timezone-naive” timestamps which need to be converted to “timezone-aware”
timestamps (see for example the definition
in the Python documentation).
Input timestamps are assumed to be relative to the timezone given in
AssumeTimezoneOptions::timezone
. They are converted to
UTC-relative timestamps with the timezone metadata set to the above value.
An error is returned if the timestamps already have the timezone metadata set.
local_timestamp
function converts UTC-relative timestamps to local “timezone-naive”
timestamps. The timezone is taken from the timezone metadata of the input
timestamps. This function is the inverse of assume_timezone
. Please note:
all temporal functions already operate on timestamps as if they were in local
time of the metadata provided timezone. Using local_timestamp
is only meant to be
used when an external system expects local timestamps.
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
assume_timezone |
Unary |
Timestamp |
Timestamp |
(1) |
|
local_timestamp |
Unary |
Timestamp |
Timestamp |
(2) |
(1) In addition to the timezone value,
AssumeTimezoneOptions
allows choosing the behaviour when a timestamp is ambiguous or nonexistent in the given timezone (because of DST shifts).
Random number generation#
This function generates an array of uniformly-distributed double-precision numbers in range [0, 1). The options provide the length of the output and the algorithm for generating the random numbers, using either a seed or a system-provided, platform-specific random generator.
Function name |
Arity |
Output type |
Options class |
---|---|---|---|
random |
Nullary |
Float64 |
Array-wise (“vector”) functions#
Cumulative Functions#
Cumulative functions are vector functions that perform a running accumulation on
their input using a given binary associative operation with an identity element
(a monoid) and output an array containing the corresponding intermediate running
values. The input is expected to be of numeric type. By default these functions
do not detect overflow. They are also available in an overflow-checking variant,
suffixed _checked
, which returns an Invalid
Status
when
overflow is detected.
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
cumulative_sum |
Unary |
Numeric |
Numeric |
(1) |
|
cumulative_sum_checked |
Unary |
Numeric |
Numeric |
(1) |
|
cumulative_prod |
Unary |
Numeric |
Numeric |
(1) |
|
cumulative_prod_checked |
Unary |
Numeric |
Numeric |
(1) |
|
cumulative_max |
Unary |
Numeric |
Numeric |
(1) |
|
cumulative_min |
Unary |
Numeric |
Numeric |
(1) |
|
cumulative_mean |
Unary |
Numeric |
Float64 |
(1) (2) |
(1) CumulativeOptions has two optional parameters. The first parameter
CumulativeOptions::start
is a starting value for the running accumulation. It has a default value of 0 forsum
, 1 forprod
, min of input type formax
, and max of input type formin
. Specified values ofstart
must be castable to the input type. The second parameterCumulativeOptions::skip_nulls
is a boolean. When set to false (the default), the first encountered null is propagated. When set to true, each null in the input produces a corresponding null in the output and doesn’t affect the accumulation forward.(2)
CumulativeOptions::start
is ignored.
Associative transforms#
Function name |
Arity |
Input types |
Output type |
Notes |
---|---|---|---|---|
dictionary_encode |
Unary |
Boolean, Null, Numeric, Temporal, Binary- and String-like |
Dictionary |
(1) |
unique |
Unary |
Boolean, Null, Numeric, Temporal, Binary- and String-like |
Input type |
(2) |
value_counts |
Unary |
Boolean, Null, Numeric, Temporal, Binary- and String-like |
Input type |
(3) |
(1) Output is
Dictionary(Int32, input type)
. It is a no-op if input is already a Dictionary array.(2) Duplicates are removed from the output while the original order is maintained.
(3) Output is a
{"values": input type, "counts": Int64}
Struct. Each output element corresponds to a unique value in the input, along with the number of times this value has appeared.
Selections#
These functions select and return a subset of their input.
Function name |
Arity |
Input type 1 |
Input type 2 |
Output type |
Options class |
Notes |
---|---|---|---|---|---|---|
array_filter |
Binary |
Any |
Boolean |
Input type 1 |
(2) |
|
array_take |
Binary |
Any |
Integer |
Input type 1 |
(3) |
|
drop_null |
Unary |
Any |
Input type 1 |
(1) |
||
filter |
Binary |
Any |
Boolean |
Input type 1 |
(2) |
|
take |
Binary |
Any |
Integer |
Input type 1 |
(3) |
(1) Each element in the input is appended to the output iff it is non-null. If the input is a record batch or table, any null value in a column drops the entire row.
(2) Each element in input 1 (the values) is appended to the output iff the corresponding element in input 2 (the filter) is true. How nulls in the filter are handled can be configured using FilterOptions.
(3) For each element i in input 2 (the indices), the i’th element in input 1 (the values) is appended to the output.
Containment tests#
This function returns the indices at which array elements are non-null and non-zero.
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
indices_nonzero |
Unary |
Boolean, Null, Numeric, Decimal |
UInt64 |
Sorts and partitions#
By default, in these functions, nulls are considered greater than any other value
(they will be sorted or partitioned at the end of the array). Floating-point
NaN values are considered greater than any other non-null value, but smaller
than nulls. This behaviour can be changed using the null_placement
setting
in the respective option classes.
Note
Binary- and String-like inputs are ordered lexicographically as bytestrings, even for String types.
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
array_sort_indices |
Unary |
Boolean, Numeric, Temporal, Binary- and String-like |
UInt64 |
(1) (2) |
|
partition_nth_indices |
Unary |
Boolean, Numeric, Temporal, Binary- and String-like |
UInt64 |
(3) |
|
rank |
Unary |
Boolean, Numeric, Temporal, Binary- and String-like |
UInt64 |
(4) |
|
select_k_unstable |
Unary |
Boolean, Numeric, Temporal, Binary- and String-like |
UInt64 |
(5) (6) |
|
sort_indices |
Unary |
Boolean, Numeric, Temporal, Binary- and String-like |
UInt64 |
(1) (5) |
(1) The output is an array of indices into the input, that define a stable sort of the input.
(2) The input must be an array. The default order is ascending.
(3) The output is an array of indices into the input array, that define a partial non-stable sort such that the N’th index points to the N’th element in sorted order, and all indices before the N’th point to elements less or equal to elements at or after the N’th (similar to
std::nth_element()
). N is given inPartitionNthOptions::pivot
.(4) The output is a one-based numerical array of ranks
(5) The input can be an array, chunked array, record batch or table. If the input is a record batch or table, one or more sort keys must be specified.
(6) The output is an array of indices into the input, that define a non-stable sort of the input.
Structural transforms#
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
list_element |
Binary |
List-like (Arg 0), Integral (Arg 1) |
List value type |
(1) |
|
list_flatten |
Unary |
List-like |
List value type |
(2) |
|
list_parent_indices |
Unary |
List-like |
Int64 |
(3) |
|
list_slice |
Unary |
List-like |
List-like |
(4) |
|
map_lookup |
Unary |
Map |
Computed |
(5) |
|
struct_field |
Unary |
Struct or Union |
Computed |
(6) |
(1) Output is an array of the same length as the input list array. The output values are the values at the specified index of each child list.
(2) The top level of nesting is removed: all values in the list child array, including nulls, are appended to the output. However, nulls in the parent list array are discarded.
(3) For each value in the list child array, the index at which it is found in the list-like array is appended to the output. Indices of null lists in the parent array might still be present in the output if they are non-empty null lists. If the parent is a list-view, child array values that are not used by any non-null list-view are null in the output.
(4) For each list element, compute the slice of that list element, then return another list-like array of those slices. Can return either a fixed or variable size list-like array, as determined by options provided.
(5) Extract either the
FIRST
,LAST
orALL
items from a map whose key match the given query key passed via options. The output type is an Array of items for theFIRST
/LAST
options and an Array of List of items for theALL
option.(6) Extract a child value based on a sequence of indices passed in the options. The validity bitmap of the result will be the intersection of all intermediate validity bitmaps. For example, for an array with type
struct<a: int32, b: struct<c: int64, d: float64>>
:An empty sequence of indices yields the original value unchanged.
The index
0
yields an array of typeint32
whose validity bitmap is the intersection of the bitmap for the outermost struct and the bitmap for the childa
.The index
1, 1
yields an array of typefloat64
whose validity bitmap is the intersection of the bitmaps for the outermost struct, for structb
, and for the childd
.
For unions, a validity bitmap is synthesized based on the type codes. Also, the index is always the child index and not a type code. Hence for array with type
sparse_union<2: int32, 7: utf8>
:The index
0
yields an array of typeint32
, which is valid at an index n if and only if the child arraya
is valid at index n and the type code at index n is 2.The indices
2
and7
are invalid.
Replace functions#
These functions create a copy of the first input with some elements replaced, based on the remaining inputs.
Function name |
Arity |
Input type 1 |
Input type 2 |
Input type 3 |
Output type |
Notes |
---|---|---|---|---|---|---|
fill_null_backward |
Unary |
Fixed-width or binary |
Input type 1 |
(1) |
||
fill_null_forward |
Unary |
Fixed-width or binary |
Input type 1 |
(1) |
||
replace_with_mask |
Ternary |
Fixed-width or binary |
Boolean |
Input type 1 |
Input type 1 |
(2) |
(1) Valid values are carried forward/backward to fill null values.
(2) Each element in input 1 for which the corresponding Boolean in input 2 is true is replaced with the next value from input 3. A null in input 2 results in a corresponding null in the output.
Also see: if_else.
Pairwise functions#
Pairwise functions are unary vector functions that perform a binary operation on a pair of elements in the input array, typically on adjacent elements. The n-th output is computed by applying the binary operation to the n-th and (n-p)-th inputs, where p is the period. The default period is 1, in which case the binary operation is applied to adjacent pairs of inputs. The period can also be negative, in which case the n-th output is computed by applying the binary operation to the n-th and (n+abs(p))-th inputs.
Function name |
Arity |
Input types |
Output type |
Options class |
Notes |
---|---|---|---|---|---|
pairwise_diff |
Unary |
Numeric/Temporal |
Numeric/Temporal |
(1)(2) |
|
pairwise_diff_checked |
Unary |
Numeric/Temporal |
Numeric/Temporal |
(1)(3) |
(1) Computes the first order difference of an array, It internally calls the scalar function
Subtract
(or the checked variant) to compute differences, so its behavior and supported types are the same asSubtract
. The period can be specified inPairwiseOptions
.(2) Wraps around the result when overflow is detected.
(3) Returns an
Invalid
Status
when overflow is detected.