Hash Functions 

Hash functions can be used for the deterministic pseudo-random shuffling of elements.

Simhash is a hash function, which returns close hash values for close (similar) arguments.

halfMD5 

Interprets all the input parameters as strings and calculates the MD5 hash value for each of them. Then combines hashes, takes the first 8 bytes of the hash of the resulting string, and interprets them as UInt64 in big-endian byte order.

halfMD5(par1, ...)

The function is relatively slow (5 million short strings per second per processor core).
Consider using the sipHash64 function instead.

Arguments

The function takes a variable number of input parameters. Arguments can be any of the supported data types.

Returned Value

A UInt64 data type hash value.

Example

SELECT halfMD5(array('e','x','a'), 'mple', 10, toDateTime('2019-06-15 23:00:00')) AS halfMD5hash, toTypeName(halfMD5hash) AS type;
┌────────halfMD5hash─┬─type───┐
│ 186182704141653334 │ UInt64 │
└────────────────────┴────────┘

MD4 

Calculates the MD4 from a string and returns the resulting set of bytes as FixedString(16).

MD5 

Calculates the MD5 from a string and returns the resulting set of bytes as FixedString(16).
If you do not need MD5 in particular, but you need a decent cryptographic 128-bit hash, use the ‘sipHash128’ function instead.
If you want to get the same result as output by the md5sum utility, use lower(hex(MD5(s))).

sipHash64 

Produces a 64-bit SipHash hash value.

sipHash64(par1,...)

This is a cryptographic hash function. It works at least three times faster than the MD5 function.

Function interprets all the input parameters as strings and calculates the hash value for each of them. Then combines hashes by the following algorithm:

  1. After hashing all the input parameters, the function gets the array of hashes.
  2. Function takes the first and the second elements and calculates a hash for the array of them.
  3. Then the function takes the hash value, calculated at the previous step, and the third element of the initial hash array, and calculates a hash for the array of them.
  4. The previous step is repeated for all the remaining elements of the initial hash array.

Arguments

The function takes a variable number of input parameters. Arguments can be any of the supported data types.

Returned Value

A UInt64 data type hash value.

Example

SELECT sipHash64(array('e','x','a'), 'mple', 10, toDateTime('2019-06-15 23:00:00')) AS SipHash, toTypeName(SipHash) AS type;
┌──────────────SipHash─┬─type───┐
│ 13726873534472839665 │ UInt64 │
└──────────────────────┴────────┘

sipHash128 

Calculates SipHash from a string.
Accepts a String-type argument. Returns FixedString(16).
Differs from sipHash64 in that the final xor-folding state is only done up to 128 bits.

cityHash64 

Produces a 64-bit CityHash hash value.

cityHash64(par1,...)

This is a fast non-cryptographic hash function. It uses the CityHash algorithm for string parameters and implementation-specific fast non-cryptographic hash function for parameters with other data types. The function uses the CityHash combinator to get the final results.

Arguments

The function takes a variable number of input parameters. Arguments can be any of the supported data types.

Returned Value

A UInt64 data type hash value.

Examples

Call example:

SELECT cityHash64(array('e','x','a'), 'mple', 10, toDateTime('2019-06-15 23:00:00')) AS CityHash, toTypeName(CityHash) AS type;
┌─────────────CityHash─┬─type───┐
│ 12072650598913549138 │ UInt64 │
└──────────────────────┴────────┘

The following example shows how to compute the checksum of the entire table with accuracy up to the row order:

SELECT groupBitXor(cityHash64(*)) FROM table

intHash32 

Calculates a 32-bit hash code from any type of integer.
This is a relatively fast non-cryptographic hash function of average quality for numbers.

intHash64 

Calculates a 64-bit hash code from any type of integer.
It works faster than intHash32. Average quality.

SHA1, SHA224, SHA256, SHA512 

Calculates SHA-1, SHA-224, SHA-256, SHA-512 hash from a string and returns the resulting set of bytes as FixedString.

Syntax

SHA1('s')
...
SHA512('s')

The function works fairly slowly (SHA-1 processes about 5 million short strings per second per processor core, while SHA-224 and SHA-256 process about 2.2 million).
We recommend using this function only in cases when you need a specific hash function and you can’t select it.
Even in these cases, we recommend applying the function offline and pre-calculating values when inserting them into the table, instead of applying it in SELECT queries.

Arguments

  • s — Input string for SHA hash calculation. String.

Returned value

  • SHA hash as a hex-unencoded FixedString. SHA-1 returns as FixedString(20), SHA-224 as FixedString(28), SHA-256 — FixedString(32), SHA-512 — FixedString(64).

Type: FixedString.

Example

Use the hex function to represent the result as a hex-encoded string.

Query:

SELECT hex(SHA1('abc'));

Result:

┌─hex(SHA1('abc'))─────────────────────────┐
│ A9993E364706816ABA3E25717850C26C9CD0D89D │
└──────────────────────────────────────────┘

URLHash(url[, N]) 

A fast, decent-quality non-cryptographic hash function for a string obtained from a URL using some type of normalization.
URLHash(s) – Calculates a hash from a string without one of the trailing symbols /,? or # at the end, if present.
URLHash(s, N) – Calculates a hash from a string up to the N level in the URL hierarchy, without one of the trailing symbols /,? or # at the end, if present.
Levels are the same as in URLHierarchy. This function is specific to Yandex.Metrica.

farmFingerprint64 

farmHash64 

Produces a 64-bit FarmHash or Fingerprint value. farmFingerprint64 is preferred for a stable and portable value.

farmFingerprint64(par1, ...)
farmHash64(par1, ...)

These functions use the Fingerprint64 and Hash64 methods respectively from all available methods.

Arguments

The function takes a variable number of input parameters. Arguments can be any of the supported data types.

Returned Value

A UInt64 data type hash value.

Example

SELECT farmHash64(array('e','x','a'), 'mple', 10, toDateTime('2019-06-15 23:00:00')) AS FarmHash, toTypeName(FarmHash) AS type;
┌─────────────FarmHash─┬─type───┐
│ 17790458267262532859 │ UInt64 │
└──────────────────────┴────────┘

javaHash 

Calculates JavaHash from a string. This hash function is neither fast nor having a good quality. The only reason to use it is when this algorithm is already used in another system and you have to calculate exactly the same result.

Syntax

SELECT javaHash('')

Returned value

A Int32 data type hash value.

Example

Query:

SELECT javaHash('Hello, world!');

Result:

┌─javaHash('Hello, world!')─┐
│               -1880044555 │
└───────────────────────────┘

javaHashUTF16LE 

Calculates JavaHash from a string, assuming it contains bytes representing a string in UTF-16LE encoding.

Syntax

javaHashUTF16LE(stringUtf16le)

Arguments

  • stringUtf16le — a string in UTF-16LE encoding.

Returned value

A Int32 data type hash value.

Example

Correct query with UTF-16LE encoded string.

Query:

SELECT javaHashUTF16LE(convertCharset('test', 'utf-8', 'utf-16le'));

Result:

┌─javaHashUTF16LE(convertCharset('test', 'utf-8', 'utf-16le'))─┐
│                                                      3556498 │
└──────────────────────────────────────────────────────────────┘

hiveHash 

Calculates HiveHash from a string.

SELECT hiveHash('')

This is just JavaHash with zeroed out sign bit. This function is used in Apache Hive for versions before 3.0. This hash function is neither fast nor having a good quality. The only reason to use it is when this algorithm is already used in another system and you have to calculate exactly the same result.

Returned value

A Int32 data type hash value.

Type: hiveHash.

Example

Query:

SELECT hiveHash('Hello, world!');

Result:

┌─hiveHash('Hello, world!')─┐
│                 267439093 │
└───────────────────────────┘

metroHash64 

Produces a 64-bit MetroHash hash value.

metroHash64(par1, ...)

Arguments

The function takes a variable number of input parameters. Arguments can be any of the supported data types.

Returned Value

A UInt64 data type hash value.

Example

SELECT metroHash64(array('e','x','a'), 'mple', 10, toDateTime('2019-06-15 23:00:00')) AS MetroHash, toTypeName(MetroHash) AS type;
┌────────────MetroHash─┬─type───┐
│ 14235658766382344533 │ UInt64 │
└──────────────────────┴────────┘

jumpConsistentHash 

Calculates JumpConsistentHash form a UInt64.
Accepts two arguments: a UInt64-type key and the number of buckets. Returns Int32.
For more information, see the link: JumpConsistentHash

murmurHash2_32, murmurHash2_64 

Produces a MurmurHash2 hash value.

murmurHash2_32(par1, ...)
murmurHash2_64(par1, ...)

Arguments

Both functions take a variable number of input parameters. Arguments can be any of the supported data types.

Returned Value

  • The murmurHash2_32 function returns hash value having the UInt32 data type.
  • The murmurHash2_64 function returns hash value having the UInt64 data type.

Example

SELECT murmurHash2_64(array('e','x','a'), 'mple', 10, toDateTime('2019-06-15 23:00:00')) AS MurmurHash2, toTypeName(MurmurHash2) AS type;
┌──────────MurmurHash2─┬─type───┐
│ 11832096901709403633 │ UInt64 │
└──────────────────────┴────────┘

gccMurmurHash 

Calculates a 64-bit MurmurHash2 hash value using the same hash seed as gcc. It is portable between CLang and GCC builds.

Syntax

gccMurmurHash(par1, ...)

Arguments

Returned value

  • Calculated hash value.

Type: UInt64.

Example

Query:

SELECT
    gccMurmurHash(1, 2, 3) AS res1,
    gccMurmurHash(('a', [1, 2, 3], 4, (4, ['foo', 'bar'], 1, (1, 2)))) AS res2

Result:

┌─────────────────res1─┬────────────────res2─┐
│ 12384823029245979431 │ 1188926775431157506 │
└──────────────────────┴─────────────────────┘

murmurHash3_32, murmurHash3_64 

Produces a MurmurHash3 hash value.

murmurHash3_32(par1, ...)
murmurHash3_64(par1, ...)

Arguments

Both functions take a variable number of input parameters. Arguments can be any of the supported data types.

Returned Value

  • The murmurHash3_32 function returns a UInt32 data type hash value.
  • The murmurHash3_64 function returns a UInt64 data type hash value.

Example

SELECT murmurHash3_32(array('e','x','a'), 'mple', 10, toDateTime('2019-06-15 23:00:00')) AS MurmurHash3, toTypeName(MurmurHash3) AS type;
┌─MurmurHash3─┬─type───┐
│     2152717 │ UInt32 │
└─────────────┴────────┘

murmurHash3_128 

Produces a 128-bit MurmurHash3 hash value.

murmurHash3_128( expr )

Arguments

Returned Value

A FixedString(16) data type hash value.

Example

SELECT hex(murmurHash3_128('example_string')) AS MurmurHash3, toTypeName(MurmurHash3) AS type;
┌─MurmurHash3──────────────────────┬─type───┐
│ 368A1A311CB7342253354B548E7E7E71 │ String │
└──────────────────────────────────┴────────┘

xxHash32, xxHash64 

Calculates xxHash from a string. It is proposed in two flavors, 32 and 64 bits.

SELECT xxHash32('')

OR

SELECT xxHash64('')

Returned value

A Uint32 or Uint64 data type hash value.

Type: xxHash.

Example

Query:

SELECT xxHash32('Hello, world!');

Result:

┌─xxHash32('Hello, world!')─┐
│                 834093149 │
└───────────────────────────┘

See Also

ngramSimHash 

Splits a ASCII string into n-grams of ngramsize symbols and returns the n-gram simhash. Is case sensitive.

Can be used for detection of semi-duplicate strings with bitHammingDistance. The smaller is the Hamming Distance of the calculated simhashes of two strings, the more likely these strings are the same.

Syntax

ngramSimHash(string[, ngramsize])

Arguments

  • string — String. String.
  • ngramsize — The size of an n-gram. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.

Returned value

  • Hash value.

Type: UInt64.

Example

Query:

SELECT ngramSimHash('ClickHouse') AS Hash;

Result:

┌───────Hash─┐
│ 1627567969 │
└────────────┘

ngramSimHashCaseInsensitive 

Splits a ASCII string into n-grams of ngramsize symbols and returns the n-gram simhash. Is case insensitive.

Can be used for detection of semi-duplicate strings with bitHammingDistance. The smaller is the Hamming Distance of the calculated simhashes of two strings, the more likely these strings are the same.

Syntax

ngramSimHashCaseInsensitive(string[, ngramsize])

Arguments

  • string — String. String.
  • ngramsize — The size of an n-gram. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.

Returned value

  • Hash value.

Type: UInt64.

Example

Query:

SELECT ngramSimHashCaseInsensitive('ClickHouse') AS Hash;

Result:

┌──────Hash─┐
│ 562180645 │
└───────────┘

ngramSimHashUTF8 

Splits a UTF-8 string into n-grams of ngramsize symbols and returns the n-gram simhash. Is case sensitive.

Can be used for detection of semi-duplicate strings with bitHammingDistance. The smaller is the Hamming Distance of the calculated simhashes of two strings, the more likely these strings are the same.

Syntax

ngramSimHashUTF8(string[, ngramsize])

Arguments

  • string — String. String.
  • ngramsize — The size of an n-gram. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.

Returned value

  • Hash value.

Type: UInt64.

Example

Query:

SELECT ngramSimHashUTF8('ClickHouse') AS Hash;

Result:

┌───────Hash─┐
│ 1628157797 │
└────────────┘

ngramSimHashCaseInsensitiveUTF8 

Splits a UTF-8 string into n-grams of ngramsize symbols and returns the n-gram simhash. Is case insensitive.

Can be used for detection of semi-duplicate strings with bitHammingDistance. The smaller is the Hamming Distance of the calculated simhashes of two strings, the more likely these strings are the same.

Syntax

ngramSimHashCaseInsensitiveUTF8(string[, ngramsize])

Arguments

  • string — String. String.
  • ngramsize — The size of an n-gram. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.

Returned value

  • Hash value.

Type: UInt64.

Example

Query:

SELECT ngramSimHashCaseInsensitiveUTF8('ClickHouse') AS Hash;

Result:

┌───────Hash─┐
│ 1636742693 │
└────────────┘

wordShingleSimHash 

Splits a ASCII string into parts (shingles) of shinglesize words and returns the word shingle simhash. Is case sensitive.

Can be used for detection of semi-duplicate strings with bitHammingDistance. The smaller is the Hamming Distance of the calculated simhashes of two strings, the more likely these strings are the same.

Syntax

wordShingleSimHash(string[, shinglesize])

Arguments

  • string — String. String.
  • shinglesize — The size of a word shingle. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.

Returned value

  • Hash value.

Type: UInt64.

Example

Query:

SELECT wordShingleSimHash('ClickHouse® is a column-oriented database management system (DBMS) for online analytical processing of queries (OLAP).') AS Hash;

Result:

┌───────Hash─┐
│ 2328277067 │
└────────────┘

wordShingleSimHashCaseInsensitive 

Splits a ASCII string into parts (shingles) of shinglesize words and returns the word shingle simhash. Is case insensitive.

Can be used for detection of semi-duplicate strings with bitHammingDistance. The smaller is the Hamming Distance of the calculated simhashes of two strings, the more likely these strings are the same.

Syntax

wordShingleSimHashCaseInsensitive(string[, shinglesize])

Arguments

  • string — String. String.
  • shinglesize — The size of a word shingle. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.

Returned value

  • Hash value.

Type: UInt64.

Example

Query:

SELECT wordShingleSimHashCaseInsensitive('ClickHouse® is a column-oriented database management system (DBMS) for online analytical processing of queries (OLAP).') AS Hash;

Result:

┌───────Hash─┐
│ 2194812424 │
└────────────┘

wordShingleSimHashUTF8 

Splits a UTF-8 string into parts (shingles) of shinglesize words and returns the word shingle simhash. Is case sensitive.

Can be used for detection of semi-duplicate strings with bitHammingDistance. The smaller is the Hamming Distance of the calculated simhashes of two strings, the more likely these strings are the same.

Syntax

wordShingleSimHashUTF8(string[, shinglesize])

Arguments

  • string — String. String.
  • shinglesize — The size of a word shingle. Optinal. Possible values: any number from 1 to 25. Default value: 3. UInt8.

Returned value

  • Hash value.

Type: UInt64.

Example

Query:

SELECT wordShingleSimHashUTF8('ClickHouse® is a column-oriented database management system (DBMS) for online analytical processing of queries (OLAP).') AS Hash;

Result:

┌───────Hash─┐
│ 2328277067 │
└────────────┘

wordShingleSimHashCaseInsensitiveUTF8 

Splits a UTF-8 string into parts (shingles) of shinglesize words and returns the word shingle simhash. Is case insensitive.

Can be used for detection of semi-duplicate strings with bitHammingDistance. The smaller is the Hamming Distance of the calculated simhashes of two strings, the more likely these strings are the same.

Syntax

wordShingleSimHashCaseInsensitiveUTF8(string[, shinglesize])

Arguments

  • string — String. String.
  • shinglesize — The size of a word shingle. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.

Returned value

  • Hash value.

Type: UInt64.

Example

Query:

SELECT wordShingleSimHashCaseInsensitiveUTF8('ClickHouse® is a column-oriented database management system (DBMS) for online analytical processing of queries (OLAP).') AS Hash;

Result:

┌───────Hash─┐
│ 2194812424 │
└────────────┘

ngramMinHash 

Splits a ASCII string into n-grams of ngramsize symbols and calculates hash values for each n-gram. Uses hashnum minimum hashes to calculate the minimum hash and hashnum maximum hashes to calculate the maximum hash. Returns a tuple with these hashes. Is case sensitive.

Can be used for detection of semi-duplicate strings with tupleHammingDistance. For two strings: if one of the returned hashes is the same for both strings, we think that those strings are the same.

Syntax

ngramMinHash(string[, ngramsize, hashnum])

Arguments

  • string — String. String.
  • ngramsize — The size of an n-gram. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two hashes — the minimum and the maximum.

Type: Tuple(UInt64, UInt64).

Example

Query:

SELECT ngramMinHash('ClickHouse') AS Tuple;

Result:

┌─Tuple──────────────────────────────────────┐
│ (18333312859352735453,9054248444481805918) │
└────────────────────────────────────────────┘

ngramMinHashCaseInsensitive 

Splits a ASCII string into n-grams of ngramsize symbols and calculates hash values for each n-gram. Uses hashnum minimum hashes to calculate the minimum hash and hashnum maximum hashes to calculate the maximum hash. Returns a tuple with these hashes. Is case insensitive.

Can be used for detection of semi-duplicate strings with tupleHammingDistance. For two strings: if one of the returned hashes is the same for both strings, we think that those strings are the same.

Syntax

ngramMinHashCaseInsensitive(string[, ngramsize, hashnum])

Arguments

  • string — String. String.
  • ngramsize — The size of an n-gram. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two hashes — the minimum and the maximum.

Type: Tuple(UInt64, UInt64).

Example

Query:

SELECT ngramMinHashCaseInsensitive('ClickHouse') AS Tuple;

Result:

┌─Tuple──────────────────────────────────────┐
│ (2106263556442004574,13203602793651726206) │
└────────────────────────────────────────────┘

ngramMinHashUTF8 

Splits a UTF-8 string into n-grams of ngramsize symbols and calculates hash values for each n-gram. Uses hashnum minimum hashes to calculate the minimum hash and hashnum maximum hashes to calculate the maximum hash. Returns a tuple with these hashes. Is case sensitive.

Can be used for detection of semi-duplicate strings with tupleHammingDistance. For two strings: if one of the returned hashes is the same for both strings, we think that those strings are the same.

Syntax

ngramMinHashUTF8(string[, ngramsize, hashnum])

Arguments

  • string — String. String.
  • ngramsize — The size of an n-gram. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two hashes — the minimum and the maximum.

Type: Tuple(UInt64, UInt64).

Example

Query:

SELECT ngramMinHashUTF8('ClickHouse') AS Tuple;

Result:

┌─Tuple──────────────────────────────────────┐
│ (18333312859352735453,6742163577938632877) │
└────────────────────────────────────────────┘

ngramMinHashCaseInsensitiveUTF8 

Splits a UTF-8 string into n-grams of ngramsize symbols and calculates hash values for each n-gram. Uses hashnum minimum hashes to calculate the minimum hash and hashnum maximum hashes to calculate the maximum hash. Returns a tuple with these hashes. Is case insensitive.

Can be used for detection of semi-duplicate strings with tupleHammingDistance. For two strings: if one of the returned hashes is the same for both strings, we think that those strings are the same.

Syntax

ngramMinHashCaseInsensitiveUTF8(string [, ngramsize, hashnum])

Arguments

  • string — String. String.
  • ngramsize — The size of an n-gram. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two hashes — the minimum and the maximum.

Type: Tuple(UInt64, UInt64).

Example

Query:

SELECT ngramMinHashCaseInsensitiveUTF8('ClickHouse') AS Tuple;

Result:

┌─Tuple───────────────────────────────────────┐
│ (12493625717655877135,13203602793651726206) │
└─────────────────────────────────────────────┘

ngramMinHashArg 

Splits a ASCII string into n-grams of ngramsize symbols and returns the n-grams with minimum and maximum hashes, calculated by the ngramMinHash function with the same input. Is case sensitive.

Syntax

ngramMinHashArg(string[, ngramsize, hashnum])

Arguments

  • string — String. String.
  • ngramsize — The size of an n-gram. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two tuples with hashnum n-grams each.

Type: Tuple(Tuple(String), Tuple(String)).

Example

Query:

SELECT ngramMinHashArg('ClickHouse') AS Tuple;

Result:

┌─Tuple─────────────────────────────────────────────────────────────────────────┐
│ (('ous','ick','lic','Hou','kHo','use'),('Hou','lic','ick','ous','ckH','Cli')) │
└───────────────────────────────────────────────────────────────────────────────┘

ngramMinHashArgCaseInsensitive 

Splits a ASCII string into n-grams of ngramsize symbols and returns the n-grams with minimum and maximum hashes, calculated by the ngramMinHashCaseInsensitive function with the same input. Is case insensitive.

Syntax

ngramMinHashArgCaseInsensitive(string[, ngramsize, hashnum])

Arguments

  • string — String. String.
  • ngramsize — The size of an n-gram. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two tuples with hashnum n-grams each.

Type: Tuple(Tuple(String), Tuple(String)).

Example

Query:

SELECT ngramMinHashArgCaseInsensitive('ClickHouse') AS Tuple;

Result:

┌─Tuple─────────────────────────────────────────────────────────────────────────┐
│ (('ous','ick','lic','kHo','use','Cli'),('kHo','lic','ick','ous','ckH','Hou')) │
└───────────────────────────────────────────────────────────────────────────────┘

ngramMinHashArgUTF8 

Splits a UTF-8 string into n-grams of ngramsize symbols and returns the n-grams with minimum and maximum hashes, calculated by the ngramMinHashUTF8 function with the same input. Is case sensitive.

Syntax

ngramMinHashArgUTF8(string[, ngramsize, hashnum])

Arguments

  • string — String. String.
  • ngramsize — The size of an n-gram. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two tuples with hashnum n-grams each.

Type: Tuple(Tuple(String), Tuple(String)).

Example

Query:

SELECT ngramMinHashArgUTF8('ClickHouse') AS Tuple;

Result:

┌─Tuple─────────────────────────────────────────────────────────────────────────┐
│ (('ous','ick','lic','Hou','kHo','use'),('kHo','Hou','lic','ick','ous','ckH')) │
└───────────────────────────────────────────────────────────────────────────────┘

ngramMinHashArgCaseInsensitiveUTF8 

Splits a UTF-8 string into n-grams of ngramsize symbols and returns the n-grams with minimum and maximum hashes, calculated by the ngramMinHashCaseInsensitiveUTF8 function with the same input. Is case insensitive.

Syntax

ngramMinHashArgCaseInsensitiveUTF8(string[, ngramsize, hashnum])

Arguments

  • string — String. String.
  • ngramsize — The size of an n-gram. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two tuples with hashnum n-grams each.

Type: Tuple(Tuple(String), Tuple(String)).

Example

Query:

SELECT ngramMinHashArgCaseInsensitiveUTF8('ClickHouse') AS Tuple;

Result:

┌─Tuple─────────────────────────────────────────────────────────────────────────┐
│ (('ckH','ous','ick','lic','kHo','use'),('kHo','lic','ick','ous','ckH','Hou')) │
└───────────────────────────────────────────────────────────────────────────────┘

wordShingleMinHash 

Splits a ASCII string into parts (shingles) of shinglesize words and calculates hash values for each word shingle. Uses hashnum minimum hashes to calculate the minimum hash and hashnum maximum hashes to calculate the maximum hash. Returns a tuple with these hashes. Is case sensitive.

Can be used for detection of semi-duplicate strings with tupleHammingDistance. For two strings: if one of the returned hashes is the same for both strings, we think that those strings are the same.

Syntax

wordShingleMinHash(string[, shinglesize, hashnum])

Arguments

  • string — String. String.
  • shinglesize — The size of a word shingle. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two hashes — the minimum and the maximum.

Type: Tuple(UInt64, UInt64).

Example

Query:

SELECT wordShingleMinHash('ClickHouse® is a column-oriented database management system (DBMS) for online analytical processing of queries (OLAP).') AS Tuple;

Result:

┌─Tuple──────────────────────────────────────┐
│ (16452112859864147620,5844417301642981317) │
└────────────────────────────────────────────┘

wordShingleMinHashCaseInsensitive 

Splits a ASCII string into parts (shingles) of shinglesize words and calculates hash values for each word shingle. Uses hashnum minimum hashes to calculate the minimum hash and hashnum maximum hashes to calculate the maximum hash. Returns a tuple with these hashes. Is case insensitive.

Can be used for detection of semi-duplicate strings with tupleHammingDistance. For two strings: if one of the returned hashes is the same for both strings, we think that those strings are the same.

Syntax

wordShingleMinHashCaseInsensitive(string[, shinglesize, hashnum])

Arguments

  • string — String. String.
  • shinglesize — The size of a word shingle. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two hashes — the minimum and the maximum.

Type: Tuple(UInt64, UInt64).

Example

Query:

SELECT wordShingleMinHashCaseInsensitive('ClickHouse® is a column-oriented database management system (DBMS) for online analytical processing of queries (OLAP).') AS Tuple;

Result:

┌─Tuple─────────────────────────────────────┐
│ (3065874883688416519,1634050779997673240) │
└───────────────────────────────────────────┘

wordShingleMinHashUTF8 

Splits a UTF-8 string into parts (shingles) of shinglesize words and calculates hash values for each word shingle. Uses hashnum minimum hashes to calculate the minimum hash and hashnum maximum hashes to calculate the maximum hash. Returns a tuple with these hashes. Is case sensitive.

Can be used for detection of semi-duplicate strings with tupleHammingDistance. For two strings: if one of the returned hashes is the same for both strings, we think that those strings are the same.

Syntax

wordShingleMinHashUTF8(string[, shinglesize, hashnum])

Arguments

  • string — String. String.
  • shinglesize — The size of a word shingle. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two hashes — the minimum and the maximum.

Type: Tuple(UInt64, UInt64).

Example

Query:

SELECT wordShingleMinHashUTF8('ClickHouse® is a column-oriented database management system (DBMS) for online analytical processing of queries (OLAP).') AS Tuple;

Result:

┌─Tuple──────────────────────────────────────┐
│ (16452112859864147620,5844417301642981317) │
└────────────────────────────────────────────┘

wordShingleMinHashCaseInsensitiveUTF8 

Splits a UTF-8 string into parts (shingles) of shinglesize words and calculates hash values for each word shingle. Uses hashnum minimum hashes to calculate the minimum hash and hashnum maximum hashes to calculate the maximum hash. Returns a tuple with these hashes. Is case insensitive.

Can be used for detection of semi-duplicate strings with tupleHammingDistance. For two strings: if one of the returned hashes is the same for both strings, we think that those strings are the same.

Syntax

wordShingleMinHashCaseInsensitiveUTF8(string[, shinglesize, hashnum])

Arguments

  • string — String. String.
  • shinglesize — The size of a word shingle. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two hashes — the minimum and the maximum.

Type: Tuple(UInt64, UInt64).

Example

Query:

SELECT wordShingleMinHashCaseInsensitiveUTF8('ClickHouse® is a column-oriented database management system (DBMS) for online analytical processing of queries (OLAP).') AS Tuple;

Result:

┌─Tuple─────────────────────────────────────┐
│ (3065874883688416519,1634050779997673240) │
└───────────────────────────────────────────┘

wordShingleMinHashArg 

Splits a ASCII string into parts (shingles) of shinglesize words each and returns the shingles with minimum and maximum word hashes, calculated by the wordshingleMinHash function with the same input. Is case sensitive.

Syntax

wordShingleMinHashArg(string[, shinglesize, hashnum])

Arguments

  • string — String. String.
  • shinglesize — The size of a word shingle. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two tuples with hashnum word shingles each.

Type: Tuple(Tuple(String), Tuple(String)).

Example

Query:

SELECT wordShingleMinHashArg('ClickHouse® is a column-oriented database management system (DBMS) for online analytical processing of queries (OLAP).', 1, 3) AS Tuple;

Result:

┌─Tuple─────────────────────────────────────────────────────────────────┐
│ (('OLAP','database','analytical'),('online','oriented','processing')) │
└───────────────────────────────────────────────────────────────────────┘

wordShingleMinHashArgCaseInsensitive 

Splits a ASCII string into parts (shingles) of shinglesize words each and returns the shingles with minimum and maximum word hashes, calculated by the wordShingleMinHashCaseInsensitive function with the same input. Is case insensitive.

Syntax

wordShingleMinHashArgCaseInsensitive(string[, shinglesize, hashnum])

Arguments

  • string — String. String.
  • shinglesize — The size of a word shingle. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two tuples with hashnum word shingles each.

Type: Tuple(Tuple(String), Tuple(String)).

Example

Query:

SELECT wordShingleMinHashArgCaseInsensitive('ClickHouse® is a column-oriented database management system (DBMS) for online analytical processing of queries (OLAP).', 1, 3) AS Tuple;

Result:

┌─Tuple──────────────────────────────────────────────────────────────────┐
│ (('queries','database','analytical'),('oriented','processing','DBMS')) │
└────────────────────────────────────────────────────────────────────────┘

wordShingleMinHashArgUTF8 

Splits a UTF-8 string into parts (shingles) of shinglesize words each and returns the shingles with minimum and maximum word hashes, calculated by the wordShingleMinHashUTF8 function with the same input. Is case sensitive.

Syntax

wordShingleMinHashArgUTF8(string[, shinglesize, hashnum])

Arguments

  • string — String. String.
  • shinglesize — The size of a word shingle. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two tuples with hashnum word shingles each.

Type: Tuple(Tuple(String), Tuple(String)).

Example

Query:

SELECT wordShingleMinHashArgUTF8('ClickHouse® is a column-oriented database management system (DBMS) for online analytical processing of queries (OLAP).', 1, 3) AS Tuple;

Result:

┌─Tuple─────────────────────────────────────────────────────────────────┐
│ (('OLAP','database','analytical'),('online','oriented','processing')) │
└───────────────────────────────────────────────────────────────────────┘

wordShingleMinHashArgCaseInsensitiveUTF8 

Splits a UTF-8 string into parts (shingles) of shinglesize words each and returns the shingles with minimum and maximum word hashes, calculated by the wordShingleMinHashCaseInsensitiveUTF8 function with the same input. Is case insensitive.

Syntax

wordShingleMinHashArgCaseInsensitiveUTF8(string[, shinglesize, hashnum])

Arguments

  • string — String. String.
  • shinglesize — The size of a word shingle. Optional. Possible values: any number from 1 to 25. Default value: 3. UInt8.
  • hashnum — The number of minimum and maximum hashes used to calculate the result. Optional. Possible values: any number from 1 to 25. Default value: 6. UInt8.

Returned value

  • Tuple with two tuples with hashnum word shingles each.

Type: Tuple(Tuple(String), Tuple(String)).

Example

Query:

SELECT wordShingleMinHashArgCaseInsensitiveUTF8('ClickHouse® is a column-oriented database management system (DBMS) for online analytical processing of queries (OLAP).', 1, 3) AS Tuple;

Result:

┌─Tuple──────────────────────────────────────────────────────────────────┐
│ (('queries','database','analytical'),('oriented','processing','DBMS')) │
└────────────────────────────────────────────────────────────────────────┘

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