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/* This file implements a 64-bit FNV-1a hash UDF (user-defined function) for
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* MySQL. The function accepts any number of arguments and returns a 64-bit
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* unsigned integer. MySQL actually interprets the result as a signed integer,
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* but you should ignore that. I chose not to return the number as a
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* hexadecimal string because using an integer makes it possible to use it
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* efficiently with BIT_XOR().
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* The function never returns NULL, even when you give it NULL arguments.
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* To compile and install, execute the following commands. The function name
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* fnv1a_64 in the mysql command is case-sensitive! (Of course, when you
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* actually call the function, it is case-insensitive just like any other SQL
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* gcc -fPIC -Wall -I/usr/include/mysql -shared -o fnv1a_udf.so fnv1a_udf.cc
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* cp fnv1a_udf.so /lib * OR: * cp fnv1a_udf.so /usr/lib
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* mysql mysql -e "CREATE FUNCTION fnv1a_64 RETURNS INTEGER SONAME 'fnv1a_udf.so'"
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* For MySQL version 4.1 or older you must add the following flag to the gcc
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* command above: -DNO_DECIMAL_RESULT
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* Otherwise you will get an error like:
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* fnv1a_udf.cc:167: `DECIMAL_RESULT' undeclared (first use this function)
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* (See http://code.google.com/p/maatkit/issues/detail?id=89)
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* If you get the error "ERROR 1126 (HY000): Can't open shared library
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* 'fnv1a_udf.so' (errno: 22 fnv1a_udf.so: cannot open shared object file: No
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* such file or directory)" then you may need to copy the .so file to another
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* location in your system. Look at your environment's $LD_LIBRARY_PATH
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* variable for clues. If none is set, you may need to set this variable to
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* something like /lib.
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* If you get the error "ERROR 1126 (HY000): Can't open shared library
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* 'libfnv1a_udf.so' (errno: 22 /lib/libfnv1a_udf.so: undefined symbol:
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* __gxx_personality_v0)" then you may need to use g++ instead of gcc.
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* Try both /lib and /usr/lib before changing LD_LIBRARY_PATH.
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* On Mac OSX, use -dynamiclib instead of -shared and add -lstdc++ to the
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* Once installed successfully, you should be able to call the function. Here's
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* a faster alternative to MD5 hashing, with the added ability to hash multiple
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* arguments in a single call:
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* mysql> SELECT FNV1A_64('hello', 'world');
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* Here's a way to reduce an entire table to a single order-independent hash:
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* mysql> SELECT BIT_XOR(CAST(FNV1A_64(col1, col2, col3) AS UNSIGNED)) FROM tbl;
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/* The following header is from hash_64a.c:
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* hash_64 - 64 bit Fowler/Noll/Vo-0 FNV-1a hash code
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* @(#) $Revision: 5.1 $
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* @(#) $Id: hash_64a.c,v 5.1 2009/06/30 09:01:38 chongo Exp $
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* @(#) $Source: /usr/local/src/cmd/fnv/RCS/hash_64a.c,v $
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* The basis of this hash algorithm was taken from an idea sent
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* as reviewer comments to the IEEE POSIX P1003.2 committee by:
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* Phong Vo (http://www.research.att.com/info/kpv/)
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* Glenn Fowler (http://www.research.att.com/~gsf/)
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* In a subsequent ballot round:
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* Landon Curt Noll (http://www.isthe.com/chongo/)
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* improved on their algorithm. Some people tried this hash
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* and found that it worked rather well. In an EMail message
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* to Landon, they named it the ``Fowler/Noll/Vo'' or FNV hash.
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* FNV hashes are designed to be fast while maintaining a low
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* collision rate. The FNV speed allows one to quickly hash lots
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* of data while maintaining a reasonable collision rate. See:
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* http://www.isthe.com/chongo/tech/comp/fnv/index.html
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* for more details as well as other forms of the FNV hash.
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* To use the recommended 64 bit FNV-1a hash, pass FNV1A_64_INIT as the
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* Fnv64_t hashval argument to fnv_64a_buf() or fnv_64a_str().
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* Please do not copyright this code. This code is in the public domain.
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* LANDON CURT NOLL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
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* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
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* EVENT SHALL LANDON CURT NOLL BE LIABLE FOR ANY SPECIAL, INDIRECT OR
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* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
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* USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
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* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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* PERFORMANCE OF THIS SOFTWARE.
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* chongo <Landon Curt Noll> /\oo/\
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* http://www.isthe.com/chongo/
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* Share and Enjoy! :-)
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#include <my_global.h>
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/* On the first call, use this as the initial_value. */
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#define FNV1A_64_INIT 0xcbf29ce484222325ULL
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/* Default for NULLs, just so the result is never NULL. */
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#define HASH_NULL_DEFAULT 0x0a0b0c0d
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/* Magic number for the hashing. */
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#define FNV_64_PRIME 0x100000001b3ULL
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ulonglong hash64a(const void *buf, size_t len, ulonglong hval);
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my_bool fnv1a_64_init(UDF_INIT* initid, UDF_ARGS* args, char* message);
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ulonglong fnv1a_64(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error );
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/* Implementations */
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ulonglong hash64a(const void *buf, size_t len, ulonglong hval) {
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const unsigned char *bp = (const unsigned char*)buf;
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const unsigned char *be = bp + len;
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/* FNV-1a hash each octet of the buffer */
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for (; bp != be; ++bp) {
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/* xor the bottom with the current octet */
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hval ^= (ulonglong)*bp;
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/* multiply by the 64 bit FNV magic prime mod 2^64 */
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hval *= FNV_64_PRIME;
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fnv1a_64_init(UDF_INIT* initid, UDF_ARGS* args, char* message) {
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if (args->arg_count == 0 ) {
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strcpy(message,"FNV1A_64 requires at least one argument");
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initid->maybe_null = 0; /* The result will never be NULL */
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fnv1a_64(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error) {
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uint null_default = HASH_NULL_DEFAULT;
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ulonglong result = FNV1A_64_INIT;
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for (i = 0 ; i < args->arg_count; ++i ) {
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if ( args->args[i] != NULL ) {
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switch ( args->arg_type[i] ) {
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#ifdef NO_DECIMAL_RESULT
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= hash64a((const void*) args->args[i], args->lengths[i], result);
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real_val = *((double*) args->args[i]);
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= hash64a((const void*)&real_val, sizeof(double), result);
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int_val = *((long long*) args->args[i]);
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result = hash64a((const void*)&int_val, sizeof(ulonglong), result);
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= hash64a((const void*)&null_default, sizeof(null_default), result);
added
removed
UDF/src/fnv1a_udf.cc
