Expression API — Apache DataFusion documentation (original) (raw)
DataFrame methods such as select and filter accept one or more logical expressions and there are many functions available for creating logical expressions. These are documented below.
Tip
Most functions and methods may receive and return an Expr, which can be chained together using a fluent-style API:
use datafusion::prelude::*;
// create the expression (a > 6) AND (b < 7)
col("a").gt(lit(6)).and(col("b").lt(lit(7)));
Identifiers¶
| Syntax | Description |
|---|---|
| col(ident) | Reference a column in a dataframe col("a") |
Note
ident
A type which implement Into<Column> trait
Literal Values¶
| Syntax | Description |
|---|---|
| lit(value) | Literal value such as lit(123) or lit("hello") |
Note
value
A type which implement Literal
Boolean Expressions¶
| Syntax | Description |
|---|---|
| and(x, y), x.and(y) | Logical AND |
| or(x, y), x.or(y) | Logical OR |
| !x, not(x), x.not() | Logical NOT |
Note
! is a bitwise or logical complement operator in Rust, but it only works as a logical NOT in expression API.
Note
Since && and || are logical operators in Rust and cannot be overloaded these are not available in the expression API.
Bitwise Expressions¶
| Syntax | Description |
|---|---|
| x & y, bitwise_and(x, y), x.bitand(y) | AND |
| x | y, bitwise_or(x, y), x.bitor(y) | OR |
| x ^ y, bitwise_xor(x, y), x.bitxor(y) | XOR |
| x << y, bitwise_shift_left(x, y), x.shl(y) | Left shift |
| x >> y, bitwise_shift_right(x, y), x.shr(y) | Right shift |
Comparison Expressions¶
| Syntax | Description |
|---|---|
| x.eq(y) | Equal |
| x.not_eq(y) | Not Equal |
| x.gt(y) | Greater Than |
| x.gt_eq(y) | Greater Than or Equal |
| x.lt(y) | Less Than |
| x.lt_eq(y) | Less Than or Equal |
Note
Comparison operators (<, <=, ==, >=, >) could be overloaded by the PartialOrd and PartialEq trait in Rust, but these operators always return a bool which makes them not work with the expression API.
Arithmetic Expressions¶
| Syntax | Description |
|---|---|
| x + y, x.add(y) | Addition |
| x - y, x.sub(y) | Subtraction |
| x * y, x.mul(y) | Multiplication |
| x / y, x.div(y) | Division |
| x % y, x.rem(y) | Remainder |
| -x, x.neg() | Negation |
Math Functions¶
| Syntax | Description |
|---|---|
| abs(x) | absolute value |
| acos(x) | inverse cosine |
| acosh(x) | inverse hyperbolic cosine |
| asin(x) | inverse sine |
| asinh(x) | inverse hyperbolic sine |
| atan(x) | inverse tangent |
| atanh(x) | inverse hyperbolic tangent |
| atan2(y, x) | inverse tangent of y / x |
| cbrt(x) | cube root |
| ceil(x) | nearest integer greater than or equal to argument |
| cos(x) | cosine |
| cosh(x) | hyperbolic cosine |
| degrees(x) | converts radians to degrees |
| exp(x) | exponential |
| factorial(x) | factorial |
| floor(x) | nearest integer less than or equal to argument |
| gcd(x, y) | greatest common divisor |
| isnan(x) | predicate determining whether NaN/-NaN or not |
| iszero(x) | predicate determining whether 0.0/-0.0 or not |
| lcm(x, y) | least common multiple |
| ln(x) | natural logarithm |
| log(base, x) | logarithm of x for a particular base |
| log10(x) | base 10 logarithm |
| log2(x) | base 2 logarithm |
| nanvl(x, y) | returns x if x is not NaN otherwise returns y |
| pi() | approximate value of π |
| power(base, exponent) | base raised to the power of exponent |
| radians(x) | converts degrees to radians |
| round(x) | round to nearest integer |
| signum(x) | sign of the argument (-1, 0, +1) |
| sin(x) | sine |
| sinh(x) | hyperbolic sine |
| sqrt(x) | square root |
| tan(x) | tangent |
| tanh(x) | hyperbolic tangent |
| trunc(x) | truncate toward zero |
Note
Unlike to some databases the math functions in Datafusion works the same way as Rust math functions, avoiding failing on corner cases e.g.
select log(-1), log(0), sqrt(-1); +----------------+---------------+-----------------+ | log(Int64(-1)) | log(Int64(0)) | sqrt(Int64(-1)) | +----------------+---------------+-----------------+ | NaN | -inf | NaN | +----------------+---------------+-----------------+
Conditional Expressions¶
| Syntax | Description |
|---|---|
| coalesce([value, …]) | Returns the first of its arguments that is not null. Null is returned only if all arguments are null. It is often used to substitute a default value for null values when data is retrieved for display. |
| case(expr) .when(expr) .end(),case(expr) .when(expr) .otherwise(expr) | CASE expression. The expression may chain multiple when expressions and end with an end or otherwise expression. Example: case(col(“a”) % lit(3)) .when(lit(0), lit(“A”)) .when(lit(1), lit(“B”)) .when(lit(2), lit(“C”)) .end()or, end with otherwise to match any other conditions: case(col(“b”).gt(lit(100))) .when(lit(true), lit(“value > 100”)) .otherwise(lit(“value <= 100”)) |
| nullif(value1, value2) | Returns a null value if value1 equals value2; otherwise it returns value1. This can be used to perform the inverse operation of the coalesce expression. |
String Expressions¶
| Syntax | Description |
|---|---|
| ascii(character) | Returns a numeric representation of the character (character). Example: ascii('a') -> 97 |
| bit_length(text) | Returns the length of the string (text) in bits. Example: bit_length('spider') -> 48 |
| btrim(text, characters) | Removes all specified characters (characters) from both the beginning and the end of the string (text). Example: btrim('aabchelloccb', 'abc') -> hello |
| char_length(text) | Returns number of characters in the string (text). The same as character_length and length. Example: character_length('lion') -> 4 |
| character_length(text) | Returns number of characters in the string (text). The same as char_length and length. Example: char_length('lion') -> 4 |
| concat(value1, [value2 [, …]]) | Concatenates the text representations (value1, [value2 [, ...]]) of all the arguments. NULL arguments are ignored. Example: concat('aaa', 'bbc', NULL, 321) -> aaabbc321 |
| concat_ws(separator, value1, [value2 [, …]]) | Concatenates the text representations (value1, [value2 [, ...]]) of all the arguments with the separator (separator). NULL arguments are ignored. concat_ws('/', 'path', 'to', NULL, 'my', 'folder', 123) -> path/to/my/folder/123 |
| chr(integer) | Returns a character by its numeric representation (integer). Example: chr(90) -> 8 |
| initcap | Converts the first letter of each word to upper case and the rest to lower case. Example: initcap('hi TOM') -> Hi Tom |
| left(text, number) | Returns a certain number (number) of first characters (text). Example: left('like', 2) -> li |
| length(text) | Returns number of characters in the string (text). The same as character_length and char_length. Example: length('lion') -> 4 |
| lower(text) | Converts all characters in the string (text) into lower case. Example: lower('HELLO') -> hello |
| lpad(text, length, [, fill]) | Extends the string to length (length) by prepending the characters (fill) (a space by default). Example: lpad('bb', 5, 'a') → aaabb |
| ltrim(text, text) | Removes all specified characters (characters) from the beginning of the string (text). Example: ltrim('aabchelloccb', 'abc') -> helloccb |
| md5(text) | Computes the MD5 hash of the argument (text). |
| octet_length(text) | Returns number of bytes in the string (text). |
| repeat(text, number) | Repeats the string the specified number of times. Example: repeat('1', 4) -> 1111 |
| replace(string, from, to) | Replaces a specified string (from) with another specified string (to) in the string (string). Example: replace('Hello', 'replace', 'el') -> Hola |
| reverse(text) | Reverses the order of the characters in the string (text). Example: reverse('hello') -> olleh |
| right(text, number) | Returns a certain number (number) of last characters (text). Example: right('like', 2) -> ke |
| rpad(text, length, [, fill]) | Extends the string to length (length) by prepending the characters (fill) (a space by default). Example: rpad('bb', 5, 'a') → bbaaa |
| rtrim | Removes all specified characters (characters) from the end of the string (text). Example: rtrim('aabchelloccb', 'abc') -> aabchello |
| digest(input, algorithm) | Computes the binary hash of input, using the algorithm. |
| split_part(string, delimiter, index) | Splits the string (string) based on a delimiter (delimiter) and picks out the desired field based on the index (index). |
| starts_with(string, prefix) | Returns true if the string (string) starts with the specified prefix (prefix). If not, it returns false. Example: starts_with('Hi Tom', 'Hi') -> true |
| strpos | Finds the position from where the substring matches the string |
| substr(string, position, [, length]) | Returns substring from the position (position) with length (length) characters in the string (string). |
| translate(string, from, to) | Replaces the characters in from with the counterpart in to. Example: translate('abcde', 'acd', '15') -> 1b5e |
| trim(string) | Removes all characters, space by default from the string (string) |
| upper | Converts all characters in the string into upper case. Example: upper('hello') -> HELLO |
Array Expressions¶
| Syntax | Description |
|---|---|
| array_any_value(array) | Returns the first non-null element in the array. array_any_value([NULL, 1, 2, 3]) -> 1 |
| array_append(array, element) | Appends an element to the end of an array. array_append([1, 2, 3], 4) -> [1, 2, 3, 4] |
| array_concat(array[, …, array_n]) | Concatenates arrays. array_concat([1, 2, 3], [4, 5, 6]) -> [1, 2, 3, 4, 5, 6] |
| array_has(array, element) | Returns true if the array contains the element array_has([1,2,3], 1) -> true |
| array_has_all(array, sub-array) | Returns true if all elements of sub-array exist in array array_has_all([1,2,3], [1,3]) -> true |
| array_has_any(array, sub-array) | Returns true if any elements exist in both arrays array_has_any([1,2,3], [1,4]) -> true |
| array_dims(array) | Returns an array of the array’s dimensions. array_dims([[1, 2, 3], [4, 5, 6]]) -> [2, 3] |
| array_distinct(array) | Returns distinct values from the array after removing duplicates. array_distinct([1, 3, 2, 3, 1, 2, 4]) -> [1, 2, 3, 4] |
| array_element(array, index) | Extracts the element with the index n from the array array_element([1, 2, 3, 4], 3) -> 3 |
| empty(array) | Returns true for an empty array or false for a non-empty array. empty([1]) -> false |
| flatten(array) | Converts an array of arrays to a flat array flatten([[1], [2, 3], [4, 5, 6]]) -> [1, 2, 3, 4, 5, 6] |
| array_length(array, dimension) | Returns the length of the array dimension. array_length([1, 2, 3, 4, 5]) -> 5 |
| array_ndims(array) | Returns the number of dimensions of the array. array_ndims([[1, 2, 3], [4, 5, 6]]) -> 2 |
| array_pop_front(array) | Returns the array without the first element. array_pop_front([1, 2, 3]) -> [2, 3] |
| array_pop_back(array) | Returns the array without the last element. array_pop_back([1, 2, 3]) -> [1, 2] |
| array_position(array, element) | Searches for an element in the array, returns first occurrence. array_position([1, 2, 2, 3, 4], 2) -> 2 |
| array_positions(array, element) | Searches for an element in the array, returns all occurrences. array_positions([1, 2, 2, 3, 4], 2) -> [2, 3] |
| array_prepend(element, array) | Prepends an element to the beginning of an array. array_prepend(1, [2, 3, 4]) -> [1, 2, 3, 4] |
| array_repeat(element, count) | Returns an array containing element count times. array_repeat(1, 3) -> [1, 1, 1] |
| array_remove(array, element) | Removes the first element from the array equal to the given value. array_remove([1, 2, 2, 3, 2, 1, 4], 2) -> [1, 2, 3, 2, 1, 4] |
| array_remove_n(array, element, max) | Removes the first max elements from the array equal to the given value. array_remove_n([1, 2, 2, 3, 2, 1, 4], 2, 2) -> [1, 3, 2, 1, 4] |
| array_remove_all(array, element) | Removes all elements from the array equal to the given value. array_remove_all([1, 2, 2, 3, 2, 1, 4], 2) -> [1, 3, 1, 4] |
| array_replace(array, from, to) | Replaces the first occurrence of the specified element with another specified element. array_replace([1, 2, 2, 3, 2, 1, 4], 2, 5) -> [1, 5, 2, 3, 2, 1, 4] |
| array_replace_n(array, from, to, max) | Replaces the first max occurrences of the specified element with another specified element. array_replace_n([1, 2, 2, 3, 2, 1, 4], 2, 5, 2) -> [1, 5, 5, 3, 2, 1, 4] |
| array_replace_all(array, from, to) | Replaces all occurrences of the specified element with another specified element. array_replace_all([1, 2, 2, 3, 2, 1, 4], 2, 5) -> [1, 5, 5, 3, 5, 1, 4] |
| array_slice(array, begin,end) | Returns a slice of the array. array_slice([1, 2, 3, 4, 5, 6, 7, 8], 3, 6) -> [3, 4, 5, 6] |
| array_slice(array, begin, end, stride) | Returns a slice of the array with added stride feature. array_slice([1, 2, 3, 4, 5, 6, 7, 8], 3, 6, 2) -> [3, 5, 6] |
| array_to_string(array, delimiter) | Converts each element to its text representation. array_to_string([1, 2, 3, 4], ',') -> 1,2,3,4 |
| array_intersect(array1, array2) | Returns an array of the elements in the intersection of array1 and array2. array_intersect([1, 2, 3, 4], [5, 6, 3, 4]) -> [3, 4] |
| array_union(array1, array2) | Returns an array of the elements in the union of array1 and array2 without duplicates. array_union([1, 2, 3, 4], [5, 6, 3, 4]) -> [1, 2, 3, 4, 5, 6] |
| array_except(array1, array2) | Returns an array of the elements that appear in the first array but not in the second. array_except([1, 2, 3, 4], [5, 6, 3, 4]) -> [1, 2] |
| array_resize(array, size, value) | Resizes the list to contain size elements. Initializes new elements with value or empty if value is not set. array_resize([1, 2, 3], 5, 0) -> [1, 2, 3, 0, 0] |
| array_sort(array, desc, null_first) | Returns sorted array. array_sort([3, 1, 2, 5, 4]) -> [1, 2, 3, 4, 5] |
| cardinality(array/map) | Returns the total number of elements in the array or map. cardinality([[1, 2, 3], [4, 5, 6]]) -> 6 |
| make_array(value1, [value2 [, …]]) | Returns an Arrow array using the specified input expressions. make_array(1, 2, 3) -> [1, 2, 3] |
| range(start [, stop, step]) | Returns an Arrow array between start and stop with step. SELECT range(2, 10, 3) -> [2, 5, 8] |
| string_to_array(array, delimiter, null_string) | Splits a string based on a delimiter and returns an array of parts. Any parts matching the optional null_string will be replaced with NULL. string_to_array('abc#def#ghi', '#', ' ') -> ['abc', 'def', 'ghi'] |
| trim_array(array, n) | Deprecated |
Regular Expressions¶
| Syntax | Description |
|---|---|
| regexp_match | Matches a regular expression against a string and returns matched substrings. |
| regexp_replace | Replaces strings that match a regular expression |
Temporal Expressions¶
| Syntax | Description |
|---|---|
| date_part | Extracts a subfield from the date. |
| date_trunc | Truncates the date to a specified level of precision. |
| from_unixtime | Returns the unix time in format. |
| to_timestamp | Converts a string to a Timestamp(_, _) |
| to_timestamp_millis | Converts a string to a Timestamp(Milliseconds, None) |
| to_timestamp_micros | Converts a string to a Timestamp(Microseconds, None) |
| to_timestamp_seconds | Converts a string to a Timestamp(Seconds, None) |
| now() | Returns current time. |
Other Expressions¶
| Syntax | Description |
|---|---|
| array([value1, …]) | Returns an array of fixed size with each argument ([value1, ...]) on it. |
| in_list(expr, list, negated) | Returns true if (expr) belongs or not belongs (negated) to a list (list), otherwise returns false. |
| random() | Returns a random value from 0 (inclusive) to 1 (exclusive). |
| sha224(text) | Computes the SHA224 hash of the argument (text). |
| sha256(text) | Computes the SHA256 hash of the argument (text). |
| sha384(text) | Computes the SHA384 hash of the argument (text). |
| sha512(text) | Computes the SHA512 hash of the argument (text). |
| to_hex(integer) | Converts the integer (integer) to the corresponding hexadecimal string. |
Aggregate Functions¶
| Syntax | Description |
|---|---|
| avg(expr) | Сalculates the average value for expr. |
| approx_distinct(expr) | Calculates an approximate count of the number of distinct values for expr. |
| approx_median(expr) | Calculates an approximation of the median for expr. |
| approx_percentile_cont(expr, percentile) | Calculates an approximation of the specified percentile for expr. |
| approx_percentile_cont_with_weight(expr, weight_expr, percentile) | Calculates an approximation of the specified percentile for expr and weight_expr. |
| bit_and(expr) | Computes the bitwise AND of all non-null input values for expr. |
| bit_or(expr) | Computes the bitwise OR of all non-null input values for expr. |
| bit_xor(expr) | Computes the bitwise exclusive OR of all non-null input values for expr. |
| bool_and(expr) | Returns true if all non-null input values (expr) are true, otherwise false. |
| bool_or(expr) | Returns true if any non-null input value (expr) is true, otherwise false. |
| count(expr) | Returns the number of rows for expr. |
| count_distinct | Creates an expression to represent the count(distinct) aggregate function |
| cube(exprs) | Creates a grouping set for all combination of exprs |
| grouping_set(exprs) | Create a grouping set. |
| max(expr) | Finds the maximum value of expr. |
| median(expr) | Сalculates the median of expr. |
| min(expr) | Finds the minimum value of expr. |
| rollup(exprs) | Creates a grouping set for rollup sets. |
| sum(expr) | Сalculates the sum of expr. |
Aggregate Function Builder¶
You can also use the ExprFunctionExt trait to more easily build Aggregate arguments Expr.
See datafusion-examples/examples/expr_api.rs for example usage.
| Syntax | Equivalent to |
|---|---|
| first_value_udaf.call(vec![expr]).order_by(vec![expr]).build().unwrap() | first_value(expr, Some(vec![expr])) |
Subquery Expressions¶
| Syntax | Description |
|---|---|
| exists | Creates an EXISTS subquery expression |
| in_subquery | df1.filter(in_subquery(col("foo"), df2))? is the equivalent of the SQL WHERE foo IN |
| not_exists | Creates a NOT EXISTS subquery expression |
| not_in_subquery | Creates a NOT IN subquery expression |
| scalar_subquery | Creates a scalar subquery expression |
User-Defined Function Expressions¶
| Syntax | Description |
|---|---|
| create_udf | Creates a new UDF with a specific signature and specific return type. |
| create_udaf | Creates a new UDAF with a specific signature, state type and return type. |