diff options
Diffstat (limited to 'storage/myisam/mi_unique.c')
| -rw-r--r-- | storage/myisam/mi_unique.c | 246 |
1 files changed, 246 insertions, 0 deletions
diff --git a/storage/myisam/mi_unique.c b/storage/myisam/mi_unique.c new file mode 100644 index 00000000..ecc2b354 --- /dev/null +++ b/storage/myisam/mi_unique.c @@ -0,0 +1,246 @@ +/* + Copyright (c) 2000, 2010, Oracle and/or its affiliates + Copyright (c) 2020, MariaDB Corporation. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; version 2 of the License. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */ + +/* Functions to check if a row is unique */ + +#include "myisamdef.h" +#include <m_ctype.h> + +my_bool mi_check_unique(MI_INFO *info, MI_UNIQUEDEF *def, const uchar *record, + ha_checksum unique_hash, my_off_t disk_pos) +{ + my_off_t lastpos=info->lastpos; + MI_KEYDEF *key= &info->s->keyinfo[def->key]; + uchar *key_buff=info->lastkey2; + DBUG_ENTER("mi_check_unique"); + + /* We need to store the hash value as a key in the record, breaking const */ + mi_unique_store(((uchar*) record)+key->seg->start, unique_hash); + _mi_make_key(info,def->key,key_buff,record,0); + + /* The above changed info->lastkey2. Inform mi_rnext_same(). */ + info->update&= ~HA_STATE_RNEXT_SAME; + + if (_mi_search(info,info->s->keyinfo+def->key,key_buff,MI_UNIQUE_HASH_LENGTH, + SEARCH_FIND,info->s->state.key_root[def->key])) + { + info->page_changed=1; /* Can't optimize read next */ + info->lastpos= lastpos; + DBUG_RETURN(0); /* No matching rows */ + } + + for (;;) + { + if (info->lastpos != disk_pos && + !(*info->s->compare_unique)(info,def,record,info->lastpos)) + { + my_errno=HA_ERR_FOUND_DUPP_UNIQUE; + info->errkey= (int) def->key; + info->dupp_key_pos= info->lastpos; + info->page_changed=1; /* Can't optimize read next */ + info->lastpos=lastpos; + DBUG_PRINT("info",("Found duplicate")); + DBUG_RETURN(1); /* Found identical */ + } + if (_mi_search_next(info,info->s->keyinfo+def->key, info->lastkey, + MI_UNIQUE_HASH_LENGTH, SEARCH_BIGGER, + info->s->state.key_root[def->key]) || + memcmp(info->lastkey, key_buff, MI_UNIQUE_HASH_LENGTH)) + { + info->page_changed=1; /* Can't optimize read next */ + info->lastpos=lastpos; + DBUG_RETURN(0); /* end of tree */ + } + } +} + + +/* + Calculate a hash for a row + + TODO + Add support for bit fields +*/ + +ha_checksum mi_unique_hash(MI_UNIQUEDEF *def, const uchar *record) +{ + const uchar *pos, *end; + ha_checksum crc= 0; + ulong seed1=0, seed2= 4; + HA_KEYSEG *keyseg; + + for (keyseg=def->seg ; keyseg < def->end ; keyseg++) + { + enum ha_base_keytype type=(enum ha_base_keytype) keyseg->type; + uint length=keyseg->length; + + if (keyseg->null_bit) + { + if (record[keyseg->null_pos] & keyseg->null_bit) + { + /* + Change crc in a way different from an empty string or 0. + (This is an optimisation; The code will work even if this isn't + done) + */ + crc=((crc << 8) + 511+ + (crc >> (8*sizeof(ha_checksum)-8))); + continue; + } + } + pos= record+keyseg->start; + if (keyseg->flag & HA_VAR_LENGTH_PART) + { + uint pack_length= keyseg->bit_start; + uint tmp_length= (pack_length == 1 ? (uint) *(uchar*) pos : + uint2korr(pos)); + pos+= pack_length; /* Skip VARCHAR length */ + set_if_smaller(length,tmp_length); + } + else if (keyseg->flag & HA_BLOB_PART) + { + uint tmp_length=_mi_calc_blob_length(keyseg->bit_start,pos); + memcpy((char**) &pos, pos+keyseg->bit_start, sizeof(char*)); + if (!length || length > tmp_length) + length=tmp_length; /* The whole blob */ + } + end= pos+length; + if (type == HA_KEYTYPE_TEXT || type == HA_KEYTYPE_VARTEXT1 || + type == HA_KEYTYPE_VARTEXT2) + { + my_ci_hash_sort(keyseg->charset, + (const uchar*) pos, length, + &seed1, &seed2); + crc^= seed1; + } + else + while (pos != end) + crc=((crc << 8) + + (((uchar) *(uchar*) pos++))) + + (crc >> (8*sizeof(ha_checksum)-8)); + } + return crc; +} + + +/* + compare unique key for two rows + + TODO + Add support for bit fields + + RETURN + 0 if both rows have equal unique value + # Rows are different +*/ + +int mi_unique_comp(MI_UNIQUEDEF *def, const uchar *a, const uchar *b, + my_bool null_are_equal) +{ + const uchar *pos_a, *pos_b, *end; + HA_KEYSEG *keyseg; + + for (keyseg=def->seg ; keyseg < def->end ; keyseg++) + { + enum ha_base_keytype type=(enum ha_base_keytype) keyseg->type; + uint a_length, b_length; + a_length= b_length= keyseg->length; + + /* If part is NULL it's regarded as different */ + if (keyseg->null_bit) + { + uint tmp; + if ((tmp=(a[keyseg->null_pos] & keyseg->null_bit)) != + (uint) (b[keyseg->null_pos] & keyseg->null_bit)) + return 1; + if (tmp) + { + if (!null_are_equal) + return 1; + continue; + } + } + pos_a= a+keyseg->start; + pos_b= b+keyseg->start; + if (keyseg->flag & HA_VAR_LENGTH_PART) + { + uint pack_length= keyseg->bit_start; + if (pack_length == 1) + { + a_length= (uint) *(uchar*) pos_a++; + b_length= (uint) *(uchar*) pos_b++; + } + else + { + a_length= uint2korr(pos_a); + b_length= uint2korr(pos_b); + pos_a+= 2; /* Skip VARCHAR length */ + pos_b+= 2; + } + set_if_smaller(a_length, keyseg->length); /* Safety */ + set_if_smaller(b_length, keyseg->length); /* safety */ + } + else if (keyseg->flag & HA_BLOB_PART) + { + /* Only compare 'length' characters if length != 0 */ + a_length= _mi_calc_blob_length(keyseg->bit_start,pos_a); + b_length= _mi_calc_blob_length(keyseg->bit_start,pos_b); + /* Check that a and b are of equal length */ + if (keyseg->length) + { + /* + This is used in some cases when we are not interested in comparing + the whole length of the blob. + */ + set_if_smaller(a_length, keyseg->length); + set_if_smaller(b_length, keyseg->length); + } + memcpy((char**) &pos_a, pos_a+keyseg->bit_start, sizeof(char*)); + memcpy((char**) &pos_b, pos_b+keyseg->bit_start, sizeof(char*)); + } + if (type == HA_KEYTYPE_TEXT/*The CHAR data type*/) + { + if (ha_compare_char_fixed(keyseg->charset, + (uchar *) pos_a, a_length, + (uchar *) pos_b, b_length, + keyseg->length / keyseg->charset->mbmaxlen, + FALSE/*b_is_prefix*/)) + return 1; + } + else if (type == HA_KEYTYPE_VARTEXT1 || + type == HA_KEYTYPE_VARTEXT2) + { + if (ha_compare_char_varying(keyseg->charset, + (uchar *) pos_a, a_length, + (uchar *) pos_b, b_length, + FALSE/*b_is_prefix*/)) + return 1; + } + else + { + if (a_length != b_length) + return 1; + end= pos_a+a_length; + while (pos_a != end) + { + if (*pos_a++ != *pos_b++) + return 1; + } + } + } + return 0; +} |