mirror of https://github.com/ClickHouse/ClickHouse.git synced 2024-12-12 09:22:05 +00:00

Alexander Tokmakov 9a2b3afb7e

Revert "Fix msan issue in keyed siphash"

2023-06-01 15:02:32 +03:00

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slug	sidebar_position	sidebar_label
/en/sql-reference/functions/hash-functions	85	Hash

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. For some data types calculated value of hash function may be the same for the same values even if types of arguments differ (integers of different size, named and unnamed Tuple with the same data, Map and the corresponding Array(Tuple(key, value)) type with the same data).

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 (#hash_functions-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 hash function.

The function interprets all the input parameters as strings and calculates the hash value for each of them. It then combines the hashes by the following algorithm:

The first and the second hash value are concatenated to an array which is hashed.
The previously calculated hash value and the hash of the third input parameter are hashed in a similar way.
This calculation is repeated for all remaining hash values of the original input.

Arguments

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

Returned Value

A UInt64 data type hash value.

Note that the calculated hash values may be equal for the same input values of different argument types. This affects for example integer types of different size, named and unnamed Tuple with the same data, Map and the corresponding Array(Tuple(key, value)) type with the same data.

Example

SELECT sipHash64(array('e','x','a'), 'mple', 10, toDateTime('2019-06-15 23:00:00')) AS SipHash, toTypeName(SipHash) AS type;

┌──────────────SipHash─┬─type───┐
│ 11400366955626497465 │ UInt64 │
└──────────────────────┴────────┘

sipHash64Keyed

Same as sipHash64 but additionally takes an explicit key argument instead of using a fixed key.

Syntax

sipHash64Keyed((k0, k1), par1,...)

Arguments

Same as sipHash64, but the first argument is a tuple of two UInt64 values representing the key.

Returned value

A UInt64 data type hash value.

Example

Query:

SELECT sipHash64Keyed((506097522914230528, 1084818905618843912), array('e','x','a'), 'mple', 10, toDateTime('2019-06-15 23:00:00')) AS SipHash, toTypeName(SipHash) AS type;

┌─────────────SipHash─┬─type───┐
│ 8017656310194184311 │ UInt64 │
└─────────────────────┴────────┘

sipHash128

Like sipHash64 but produces a 128-bit hash value, i.e. the final xor-folding state is done up to 128 bits.

:::note This 128-bit variant differs from the reference implementation and it's weaker. This version exists because, when it was written, there was no official 128-bit extension for SipHash. New projects should probably use sipHash128Reference. :::

Syntax

sipHash128(par1,...)

Arguments

Same as for sipHash64.

Returned value

A 128-bit SipHash hash value of type FixedString(16).

Example

Query:

SELECT hex(sipHash128('foo', '\x01', 3));

Result:

┌─hex(sipHash128('foo', '', 3))────┐
│ 9DE516A64A414D4B1B609415E4523F24 │
└──────────────────────────────────┘

sipHash128Keyed

Same as sipHash128 but additionally takes an explicit key argument instead of using a fixed key.

Syntax

sipHash128Keyed((k0, k1), par1,...)

Arguments

Same as sipHash128, but the first argument is a tuple of two UInt64 values representing the key.

Returned value

A 128-bit SipHash hash value of type FixedString(16).

Example

Query:

SELECT hex(sipHash128Keyed((506097522914230528, 1084818905618843912),'foo', '\x01', 3));

Result:

┌─hex(sipHash128Keyed((506097522914230528, 1084818905618843912), 'foo', '', 3))─┐
│ B8467F65C8B4CFD9A5F8BD733917D9BF                                              │
└───────────────────────────────────────────────────────────────────────────────┘

sipHash128Reference

Like sipHash128 but implements the 128-bit algorithm from the original authors of SipHash.

Syntax

sipHash128Reference(par1,...)

Arguments

Same as for sipHash128.

Returned value

A 128-bit SipHash hash value of type FixedString(16).

Example

Query:

SELECT hex(sipHash128Reference('foo', '\x01', 3));

Result:

┌─hex(sipHash128Reference('foo', '', 3))─┐
│ 4D1BE1A22D7F5933C0873E1698426260       │
└────────────────────────────────────────┘

sipHash128ReferenceKeyed

Same as sipHash128Reference but additionally takes an explicit key argument instead of using a fixed key.

Syntax

sipHash128ReferenceKeyed((k0, k1), par1,...)

Arguments

Same as sipHash128Reference, but the first argument is a tuple of two UInt64 values representing the key.

Returned value

A 128-bit SipHash hash value of type FixedString(16).

Example

Query:

SELECT hex(sipHash128ReferenceKeyed((506097522914230528, 1084818905618843912),'foo', '\x01', 3));

Result:

┌─hex(sipHash128ReferenceKeyed((506097522914230528, 1084818905618843912), 'foo', '', 3))─┐
│ 630133C9722DC08646156B8130C4CDC8                                                       │
└────────────────────────────────────────────────────────────────────────────────────────┘

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.

Note that Google changed the algorithm of CityHash after it has been added to ClickHouse. In other words, ClickHouse's cityHash64 and Google's upstream CityHash now produce different results. ClickHouse cityHash64 corresponds to CityHash v1.0.2.

Arguments

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 │
└──────────────────────────────────────────┘

BLAKE3

Calculates BLAKE3 hash string and returns the resulting set of bytes as FixedString.

Syntax

BLAKE3('s')

This cryptographic hash-function is integrated into ClickHouse with BLAKE3 Rust library. The function is rather fast and shows approximately two times faster performance compared to SHA-2, while generating hashes of the same length as SHA-256.

Arguments

s - input string for BLAKE3 hash calculation. String.

Return value

BLAKE3 hash as a byte array with type FixedString(32).

Type: FixedString.

Example

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

Query:

SELECT hex(BLAKE3('ABC'))

Result:

┌─hex(BLAKE3('ABC'))───────────────────────────────────────────────┐
│ D1717274597CF0289694F75D96D444B992A096F1AFD8E7BBFA6EBB1D360FEDFC │
└──────────────────────────────────────────────────────────────────┘

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.

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

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, Byte, Short, Integer, Long. 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.

Note that Java only support calculating signed integers hash, so if you want to calculate unsigned integers hash you must cast it to proper signed ClickHouse types.

Syntax

SELECT javaHash('')

Returned value

A Int32 data type hash value.

Example

Query:

SELECT javaHash(toInt32(123));

Result:

┌─javaHash(toInt32(123))─┐
│               123      │
└────────────────────────┘

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 │
└───────────────────────────┘

Entropy-learned hashing (experimental)

Entropy-learned hashing is disabled by default, to enable: SET allow_experimental_hash_functions=1.

Entropy-learned hashing is not a standalone hash function like metroHash64, cityHash64, sipHash64 etc. Instead, it aims to preprocess the data to be hashed in a way that a standalone hash function can be computed more efficiently while not compromising the hash quality, i.e. the randomness of the hashes. For that, entropy-based hashing chooses a subset of the bytes in a training data set of Strings which has the same randomness (entropy) as the original Strings. For example, if the Strings are in average 100 bytes long, and we pick a subset of 5 bytes, then a hash function will be 95% less expensive to evaluate. For details of the method, refer to Entropy-Learned Hashing: Constant Time Hashing with Controllable Uniformity.

Entropy-learned hashing has two phases:

A training phase on a representative but typically small set of Strings to be hashed. Training consists of two steps:
- Function prepareTrainEntropyLearnedHash(data, id) caches the training data in a global state under a given id. It returns dummy value 0 on every row.
- Function trainEntropyLearnedHash(id) computes a minimal partial sub-key of the training data stored stored under id in the global state. The cached training data in the global state is replaced by the partial key. Dummy value 0 is returned on every row.
An evaluation phase where hashes are computed using the previously calculated partial sub-keys. Function entropyLearnedHash(data, id) hashes data using the partial subkey stored as id. CityHash64 is used as hash function.

The reason that the training phase comprises two steps is that ClickHouse processes data at chunk granularity but entropy-learned hashing needs to process the entire training set at once.

Since functions prepareTrainEntropyLearnedHash() and trainEntropyLearnedHash() access global state, they should not be called in parallel with the same id.

Syntax

prepareTrainEntropyLearnedHash(data, id);
trainEntropyLearnedHash(id);
entropyLearnedHash(data, id);

Example

SET allow_experimental_hash_functions=1;
CREATE TABLE tab (col String) ENGINE=Memory;
INSERT INTO tab VALUES ('aa'), ('ba'), ('ca');

SELECT prepareTrainEntropyLearnedHash(col, 'id1') AS prepared FROM tab;
SELECT trainEntropyLearnedHash('id1') AS trained FROM tab;
SELECT entropyLearnedHash(col, 'id1') as hashes FROM tab;

Result:

┌─prepared─┐
│        0 │
│        0 │
│        0 │
└──────────┘

┌─trained─┐
│       0 │
│       0 │
│       0 │
└─────────┘

┌───────────────hashes─┐
│  2603192927274642682 │
│  4947675599669400333 │
│ 10783339242466472992 │
└──────────────────────┘

metroHash64

Produces a 64-bit MetroHash hash value.

metroHash64(par1, ...)

Arguments

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. For some data types calculated value of hash function may be the same for the same values even if types of arguments differ (integers of different size, named and unnamed Tuple with the same data, Map and the corresponding Array(Tuple(key, value)) type with the same data).

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

par1, ... — A variable number of parameters that can be any of the supported data types.

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 │
└──────────────────────┴─────────────────────┘

kafkaMurmurHash

Calculates a 32-bit MurmurHash2 hash value using the same hash seed as Kafka and without the highest bit to be compatible with Default Partitioner.

Syntax

MurmurHash(par1, ...)

Arguments

par1, ... — A variable number of parameters that can be any of the supported data types.

Returned value

Calculated hash value.

Type: UInt32.

Example

Query:

SELECT
    kafkaMurmurHash('foobar') AS res1,
    kafkaMurmurHash(array('e','x','a'), 'mple', 10, toDateTime('2019-06-15 23:00:00')) AS res2

Result:

┌───────res1─┬─────res2─┐
│ 1357151166 │ 85479775 │
└────────────┴──────────┘

murmurHash3_32, murmurHash3_64

Produces a MurmurHash3 hash value.

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

Arguments

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.

Syntax

murmurHash3_128(expr)

Arguments

expr — A list of expressions. String.

Returned value

A 128-bit MurmurHash3 hash value.

Type: FixedString(16).

Example

Query:

SELECT hex(murmurHash3_128('foo', 'foo', 'foo'));

Result:

┌─hex(murmurHash3_128('foo', 'foo', 'foo'))─┐
│ F8F7AD9B6CD4CF117A71E277E2EC2931          │
└───────────────────────────────────────────┘

xxh3

Produces a 64-bit xxh3 hash value.

Syntax

xxh3(expr)

Arguments

expr — A list of expressions of any data type.

Returned value

A 64-bit xxh3 hash value.

Type: UInt64.

Example

Query:

SELECT xxh3('Hello', 'world')

Result:

┌─xxh3('Hello', 'world')─┐
│    5607458076371731292 │
└────────────────────────┘

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: UInt32 for xxHash32 and UInt64 for xxHash64.

Example

Query:

SELECT xxHash32('Hello, world!');

Result:

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

See Also

xxHash.

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.

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.

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.

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.

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.

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.

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.

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

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

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

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

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')) │
└────────────────────────────────────────────────────────────────────────┘

69 KiB Raw Blame History Unescape Escape

Hash Functions

halfMD5

MD4

MD5

sipHash64 (#hash_functions-siphash64)

sipHash64Keyed

sipHash128

sipHash128Keyed

sipHash128Reference

sipHash128ReferenceKeyed

cityHash64

intHash32

intHash64

SHA1, SHA224, SHA256, SHA512

BLAKE3

URLHash(url[, N])

farmFingerprint64

farmHash64

javaHash

javaHashUTF16LE

hiveHash

Entropy-learned hashing (experimental)

metroHash64

jumpConsistentHash

murmurHash2_32, murmurHash2_64

gccMurmurHash

kafkaMurmurHash

murmurHash3_32, murmurHash3_64

murmurHash3_128

xxh3

xxHash32, xxHash64

ngramSimHash

ngramSimHashCaseInsensitive

ngramSimHashUTF8

ngramSimHashCaseInsensitiveUTF8

wordShingleSimHash

wordShingleSimHashCaseInsensitive

wordShingleSimHashUTF8

wordShingleSimHashCaseInsensitiveUTF8

ngramMinHash

ngramMinHashCaseInsensitive

ngramMinHashUTF8

ngramMinHashCaseInsensitiveUTF8

ngramMinHashArg

ngramMinHashArgCaseInsensitive

ngramMinHashArgUTF8

ngramMinHashArgCaseInsensitiveUTF8

wordShingleMinHash

wordShingleMinHashCaseInsensitive

wordShingleMinHashUTF8

wordShingleMinHashCaseInsensitiveUTF8

wordShingleMinHashArg

wordShingleMinHashArgCaseInsensitive

wordShingleMinHashArgUTF8

wordShingleMinHashArgCaseInsensitiveUTF8

69 KiB

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