Functions for Working with Tuples
tuple
A function that allows grouping multiple columns. For columns with the types T1, T2, …, it returns a Tuple(T1, T2, …) type tuple containing these columns. There is no cost to execute the function. Tuples are normally used as intermediate values for an argument of IN operators, or for creating a list of formal parameters of lambda functions. Tuples can’t be written to a table.
The function implements the operator (x, y, …).
Syntax
tuple(x, y, …)
tupleElement
A function that allows getting a column from a tuple.
If the second argument is a number index, it is the column index, starting from 1. If the second argument is a string name, it represents the name of the element. Besides, we can provide the third optional argument, such that when index out of bounds or no element exist for the name, the default value returned instead of throwing an exception. The second and third arguments, if provided, must be constants. There is no cost to execute the function.
The function implements operators x.index and x.name.
Syntax
tupleElement(tuple, index, [, default_value])
tupleElement(tuple, name, [, default_value])
untuple
Performs syntactic substitution of tuple elements in the call location.
Syntax
untuple(x)
You can use the EXCEPT expression to skip columns as a result of the query.
Arguments
x— Atuplefunction, column, or tuple of elements. Tuple.
Returned value
- None.
Examples
Input table:
┌─key─┬─v1─┬─v2─┬─v3─┬─v4─┬─v5─┬─v6────────┐
│ 1 │ 10 │ 20 │ 40 │ 30 │ 15 │ (33,'ab') │
│ 2 │ 25 │ 65 │ 70 │ 40 │ 6 │ (44,'cd') │
│ 3 │ 57 │ 30 │ 20 │ 10 │ 5 │ (55,'ef') │
│ 4 │ 55 │ 12 │ 7 │ 80 │ 90 │ (66,'gh') │
│ 5 │ 30 │ 50 │ 70 │ 25 │ 55 │ (77,'kl') │
└─────┴────┴────┴────┴────┴────┴───────────┘
Example of using a Tuple-type column as the untuple function parameter:
Query:
SELECT untuple(v6) FROM kv;
Result:
┌─_ut_1─┬─_ut_2─┐
│ 33 │ ab │
│ 44 │ cd │
│ 55 │ ef │
│ 66 │ gh │
│ 77 │ kl │
└───────┴───────┘
Note: the names are implementation specific and are subject to change. You should not assume specific names of the columns after application of the untuple.
Example of using an EXCEPT expression:
Query:
SELECT untuple((* EXCEPT (v2, v3),)) FROM kv;
Result:
┌─key─┬─v1─┬─v4─┬─v5─┬─v6────────┐
│ 1 │ 10 │ 30 │ 15 │ (33,'ab') │
│ 2 │ 25 │ 40 │ 6 │ (44,'cd') │
│ 3 │ 57 │ 10 │ 5 │ (55,'ef') │
│ 4 │ 55 │ 80 │ 90 │ (66,'gh') │
│ 5 │ 30 │ 25 │ 55 │ (77,'kl') │
└─────┴────┴────┴────┴───────────┘
See Also
tupleHammingDistance
Returns the Hamming Distance between two tuples of the same size.
Syntax
tupleHammingDistance(tuple1, tuple2)
Arguments
Tuples should have the same type of the elements.
Returned value
- The Hamming distance.
Type: The result type is calculated the same way it is for Arithmetic functions, based on the number of elements in the input tuples.
SELECT
toTypeName(tupleHammingDistance(tuple(0), tuple(0))) AS t1,
toTypeName(tupleHammingDistance((0, 0), (0, 0))) AS t2,
toTypeName(tupleHammingDistance((0, 0, 0), (0, 0, 0))) AS t3,
toTypeName(tupleHammingDistance((0, 0, 0, 0), (0, 0, 0, 0))) AS t4,
toTypeName(tupleHammingDistance((0, 0, 0, 0, 0), (0, 0, 0, 0, 0))) AS t5
┌─t1────┬─t2─────┬─t3─────┬─t4─────┬─t5─────┐
│ UInt8 │ UInt16 │ UInt32 │ UInt64 │ UInt64 │
└───────┴────────┴────────┴────────┴────────┘
Examples
Query:
SELECT tupleHammingDistance((1, 2, 3), (3, 2, 1)) AS HammingDistance;
Result:
┌─HammingDistance─┐
│ 2 │
└─────────────────┘
Can be used with MinHash functions for detection of semi-duplicate strings:
SELECT tupleHammingDistance(wordShingleMinHash(string), wordShingleMinHashCaseInsensitive(string)) as HammingDistance FROM (SELECT 'ClickHouse is a column-oriented database management system for online analytical processing of queries.' AS string);
Result:
┌─HammingDistance─┐
│ 2 │
└─────────────────┘
tupleToNameValuePairs
Turns a named tuple into an array of (name, value) pairs. For a Tuple(a T, b T, ..., c T) returns Array(Tuple(String, T), ...)
in which the Strings represents the named fields of the tuple and T are the values associated with those names. All values in the tuple should be of the same type.
Syntax
tupleToNameValuePairs(tuple)
Arguments
tuple— Named tuple. Tuple with any types of values.
Returned value
- An array with (name, value) pairs.
Type: Array(Tuple(String, ...)).
Example
Query:
CREATE TABLE tupletest (col Tuple(user_ID UInt64, session_ID UInt64)) ENGINE = Memory;
INSERT INTO tupletest VALUES (tuple( 100, 2502)), (tuple(1,100));
SELECT tupleToNameValuePairs(col) FROM tupletest;
Result:
┌─tupleToNameValuePairs(col)────────────┐
│ [('user_ID',100),('session_ID',2502)] │
│ [('user_ID',1),('session_ID',100)] │
└───────────────────────────────────────┘
It is possible to transform columns to rows using this function:
CREATE TABLE tupletest (col Tuple(CPU Float64, Memory Float64, Disk Float64)) ENGINE = Memory;
INSERT INTO tupletest VALUES(tuple(3.3, 5.5, 6.6));
SELECT arrayJoin(tupleToNameValuePairs(col)) FROM tupletest;
Result:
┌─arrayJoin(tupleToNameValuePairs(col))─┐
│ ('CPU',3.3) │
│ ('Memory',5.5) │
│ ('Disk',6.6) │
└───────────────────────────────────────┘
If you pass a simple tuple to the function, ClickHouse uses the indexes of the values as their names:
SELECT tupleToNameValuePairs(tuple(3, 2, 1));
Result:
┌─tupleToNameValuePairs(tuple(3, 2, 1))─┐
│ [('1',3),('2',2),('3',1)] │
└───────────────────────────────────────┘
tuplePlus
Calculates the sum of corresponding values of two tuples of the same size.
Syntax
tuplePlus(tuple1, tuple2)
Alias: vectorSum.
Arguments
Returned value
- Tuple with the sum.
Type: Tuple.
Example
Query:
SELECT tuplePlus((1, 2), (2, 3));
Result:
┌─tuplePlus((1, 2), (2, 3))─┐
│ (3,5) │
└───────────────────────────┘
tupleMinus
Calculates the subtraction of corresponding values of two tuples of the same size.
Syntax
tupleMinus(tuple1, tuple2)
Alias: vectorDifference.
Arguments
Returned value
- Tuple with the result of subtraction.
Type: Tuple.
Example
Query:
SELECT tupleMinus((1, 2), (2, 3));
Result:
┌─tupleMinus((1, 2), (2, 3))─┐
│ (-1,-1) │
└────────────────────────────┘
tupleMultiply
Calculates the multiplication of corresponding values of two tuples of the same size.
Syntax
tupleMultiply(tuple1, tuple2)
Arguments
Returned value
- Tuple with the multiplication.
Type: Tuple.
Example
Query:
SELECT tupleMultiply((1, 2), (2, 3));
Result:
┌─tupleMultiply((1, 2), (2, 3))─┐
│ (2,6) │
└───────────────────────────────┘
tupleDivide
Calculates the division of corresponding values of two tuples of the same size. Note that division by zero will return inf.
Syntax
tupleDivide(tuple1, tuple2)
Arguments
Returned value
- Tuple with the result of division.
Type: Tuple.
Example
Query:
SELECT tupleDivide((1, 2), (2, 3));
Result:
┌─tupleDivide((1, 2), (2, 3))─┐
│ (0.5,0.6666666666666666) │
└─────────────────────────────┘
tupleNegate
Calculates the negation of the tuple values.
Syntax
tupleNegate(tuple)
Arguments
tuple— Tuple.
Returned value
- Tuple with the result of negation.
Type: Tuple.
Example
Query:
SELECT tupleNegate((1, 2));
Result:
┌─tupleNegate((1, 2))─┐
│ (-1,-2) │
└─────────────────────┘
tupleMultiplyByNumber
Returns a tuple with all values multiplied by a number.
Syntax
tupleMultiplyByNumber(tuple, number)
Arguments
Returned value
- Tuple with multiplied values.
Type: Tuple.
Example
Query:
SELECT tupleMultiplyByNumber((1, 2), -2.1);
Result:
┌─tupleMultiplyByNumber((1, 2), -2.1)─┐
│ (-2.1,-4.2) │
└─────────────────────────────────────┘
tupleDivideByNumber
Returns a tuple with all values divided by a number. Note that division by zero will return inf.
Syntax
tupleDivideByNumber(tuple, number)
Arguments
Returned value
- Tuple with divided values.
Type: Tuple.
Example
Query:
SELECT tupleDivideByNumber((1, 2), 0.5);
Result:
┌─tupleDivideByNumber((1, 2), 0.5)─┐
│ (2,4) │
└──────────────────────────────────┘
dotProduct
Calculates the scalar product of two tuples of the same size.
Syntax
dotProduct(tuple1, tuple2)
Alias: scalarProduct.
Arguments
Returned value
- Scalar product.
Type: Int/UInt, Float or Decimal.
Example
Query:
SELECT dotProduct((1, 2), (2, 3));
Result:
┌─dotProduct((1, 2), (2, 3))─┐
│ 8 │
└────────────────────────────┘
tupleConcat
Combines tuples passed as arguments.
tupleConcat(tuples)
Arguments
tuples– Arbitrary number of arguments of Tuple type.
Example
SELECT tupleConcat((1, 2), (3, 4), (true, false)) AS res
┌─res──────────────────┐
│ (1,2,3,4,true,false) │
└──────────────────────┘
Distance functions
All supported functions are described in distance functions documentation.