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mariadb/mysys/hash.c
konstantin@mysql.com f4cc6c4d15 Merge mysql.com:/opt/local/work/mysql-5.0-merge 
into  mysql.com:/opt/local/work/mysql-5.1-merge
2006-01-05 00:38:51 +03:00

668 lines
16 KiB
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/* Copyright (C) 2000 MySQL AB
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; either version 2 of the License, or
(at your option) any later version.
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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/* The hash functions used for saveing keys */
/* One of key_length or key_length_offset must be given */
/* Key length of 0 isn't allowed */
#include "mysys_priv.h"
#include <m_string.h>
#include <m_ctype.h>
#include "hash.h"
#define NO_RECORD ((uint) -1)
#define LOWFIND 1
#define LOWUSED 2
#define HIGHFIND 4
#define HIGHUSED 8
typedef struct st_hash_info {
uint next; /* index to next key */
byte *data; /* data for current entry */
} HASH_LINK;
static uint hash_mask(uint hashnr,uint buffmax,uint maxlength);
static void movelink(HASH_LINK *array,uint pos,uint next_link,uint newlink);
static int hashcmp(const HASH *hash, HASH_LINK *pos, const byte *key,
uint length);
static uint calc_hash(const HASH *hash, const byte *key, uint length)
{
ulong nr1=1, nr2=4;
hash->charset->coll->hash_sort(hash->charset,(uchar*) key,length,&nr1,&nr2);
return nr1;
}
my_bool
_hash_init(HASH *hash,CHARSET_INFO *charset,
uint size,uint key_offset,uint key_length,
hash_get_key get_key,
void (*free_element)(void*),uint flags CALLER_INFO_PROTO)
{
DBUG_ENTER("hash_init");
DBUG_PRINT("enter",("hash: 0x%lx size: %d",hash,size));
hash->records=0;
if (my_init_dynamic_array_ci(&hash->array,sizeof(HASH_LINK),size,0))
{
hash->free=0; /* Allow call to hash_free */
DBUG_RETURN(1);
}
hash->key_offset=key_offset;
hash->key_length=key_length;
hash->blength=1;
hash->get_key=get_key;
hash->free=free_element;
hash->flags=flags;
hash->charset=charset;
DBUG_RETURN(0);
}
/*
Call hash->free on all elements in hash.
SYNOPSIS
hash_free_elements()
hash hash table
NOTES:
Sets records to 0
*/
static inline void hash_free_elements(HASH *hash)
{
if (hash->free)
{
HASH_LINK *data=dynamic_element(&hash->array,0,HASH_LINK*);
HASH_LINK *end= data + hash->records;
while (data < end)
(*hash->free)((data++)->data);
}
hash->records=0;
}
/*
Free memory used by hash.
SYNOPSIS
hash_free()
hash the hash to delete elements of
NOTES: Hash can't be reused without calling hash_init again.
*/
void hash_free(HASH *hash)
{
DBUG_ENTER("hash_free");
DBUG_PRINT("enter",("hash: 0x%lx", hash));
hash_free_elements(hash);
hash->free= 0;
delete_dynamic(&hash->array);
DBUG_VOID_RETURN;
}
/*
Delete all elements from the hash (the hash itself is to be reused).
SYNOPSIS
my_hash_reset()
hash the hash to delete elements of
*/
void my_hash_reset(HASH *hash)
{
DBUG_ENTER("my_hash_reset");
DBUG_PRINT("enter",("hash: 0x%lxd",hash));
hash_free_elements(hash);
reset_dynamic(&hash->array);
/* Set row pointers so that the hash can be reused at once */
hash->blength= 1;
DBUG_VOID_RETURN;
}
/* some helper functions */
/*
This function is char* instead of byte* as HPUX11 compiler can't
handle inline functions that are not defined as native types
*/
static inline char*
hash_key(const HASH *hash, const byte *record, uint *length,
my_bool first)
{
if (hash->get_key)
return (*hash->get_key)(record,length,first);
*length=hash->key_length;
return (byte*) record+hash->key_offset;
}
/* Calculate pos according to keys */
static uint hash_mask(uint hashnr,uint buffmax,uint maxlength)
{
if ((hashnr & (buffmax-1)) < maxlength) return (hashnr & (buffmax-1));
return (hashnr & ((buffmax >> 1) -1));
}
static uint hash_rec_mask(const HASH *hash, HASH_LINK *pos,
uint buffmax, uint maxlength)
{
uint length;
byte *key= (byte*) hash_key(hash,pos->data,&length,0);
return hash_mask(calc_hash(hash,key,length),buffmax,maxlength);
}
/* for compilers which can not handle inline */
static
#if !defined(__USLC__) && !defined(__sgi)
inline
#endif
unsigned int rec_hashnr(HASH *hash,const byte *record)
{
uint length;
byte *key= (byte*) hash_key(hash,record,&length,0);
return calc_hash(hash,key,length);
}
gptr hash_search(const HASH *hash, const byte *key, uint length)
{
HASH_SEARCH_STATE state;
return hash_first(hash, key, length, &state);
}
/*
Search after a record based on a key
NOTE
Assigns the number of the found record to HASH_SEARCH_STATE state
*/
gptr hash_first(const HASH *hash, const byte *key, uint length,
HASH_SEARCH_STATE *current_record)
{
HASH_LINK *pos;
uint flag,idx;
DBUG_ENTER("hash_first");
flag=1;
if (hash->records)
{
idx=hash_mask(calc_hash(hash,key,length ? length : hash->key_length),
hash->blength,hash->records);
do
{
pos= dynamic_element(&hash->array,idx,HASH_LINK*);
if (!hashcmp(hash,pos,key,length))
{
DBUG_PRINT("exit",("found key at %d",idx));
*current_record= idx;
DBUG_RETURN (pos->data);
}
if (flag)
{
flag=0; /* Reset flag */
if (hash_rec_mask(hash,pos,hash->blength,hash->records) != idx)
break; /* Wrong link */
}
}
while ((idx=pos->next) != NO_RECORD);
}
*current_record= NO_RECORD;
DBUG_RETURN(0);
}
/* Get next record with identical key */
/* Can only be called if previous calls was hash_search */
gptr hash_next(const HASH *hash, const byte *key, uint length,
HASH_SEARCH_STATE *current_record)
{
HASH_LINK *pos;
uint idx;
if (*current_record != NO_RECORD)
{
HASH_LINK *data=dynamic_element(&hash->array,0,HASH_LINK*);
for (idx=data[*current_record].next; idx != NO_RECORD ; idx=pos->next)
{
pos=data+idx;
if (!hashcmp(hash,pos,key,length))
{
*current_record= idx;
return pos->data;
}
}
*current_record= NO_RECORD;
}
return 0;
}
/* Change link from pos to new_link */
static void movelink(HASH_LINK *array,uint find,uint next_link,uint newlink)
{
HASH_LINK *old_link;
do
{
old_link=array+next_link;
}
while ((next_link=old_link->next) != find);
old_link->next= newlink;
return;
}
/*
Compare a key in a record to a whole key. Return 0 if identical
SYNOPSIS
hashcmp()
hash hash table
pos position of hash record to use in comparison
key key for comparison
length length of key
NOTES:
If length is 0, comparison is done using the length of the
record being compared against.
RETURN
= 0 key of record == key
!= 0 key of record != key
*/
static int hashcmp(const HASH *hash, HASH_LINK *pos, const byte *key,
uint length)
{
uint rec_keylength;
byte *rec_key= (byte*) hash_key(hash,pos->data,&rec_keylength,1);
return ((length && length != rec_keylength) ||
my_strnncoll(hash->charset, (uchar*) rec_key, rec_keylength,
(uchar*) key, rec_keylength));
}
/* Write a hash-key to the hash-index */
my_bool my_hash_insert(HASH *info,const byte *record)
{
int flag;
uint halfbuff,hash_nr,first_index,idx;
byte *ptr_to_rec,*ptr_to_rec2;
HASH_LINK *data,*empty,*gpos,*gpos2,*pos;
LINT_INIT(gpos); LINT_INIT(gpos2);
LINT_INIT(ptr_to_rec); LINT_INIT(ptr_to_rec2);
flag=0;
if (!(empty=(HASH_LINK*) alloc_dynamic(&info->array)))
return(TRUE); /* No more memory */
data=dynamic_element(&info->array,0,HASH_LINK*);
halfbuff= info->blength >> 1;
idx=first_index=info->records-halfbuff;
if (idx != info->records) /* If some records */
{
do
{
pos=data+idx;
hash_nr=rec_hashnr(info,pos->data);
if (flag == 0) /* First loop; Check if ok */
if (hash_mask(hash_nr,info->blength,info->records) != first_index)
break;
if (!(hash_nr & halfbuff))
{ /* Key will not move */
if (!(flag & LOWFIND))
{
if (flag & HIGHFIND)
{
flag=LOWFIND | HIGHFIND;
/* key shall be moved to the current empty position */
gpos=empty;
ptr_to_rec=pos->data;
empty=pos; /* This place is now free */
}
else
{
flag=LOWFIND | LOWUSED; /* key isn't changed */
gpos=pos;
ptr_to_rec=pos->data;
}
}
else
{
if (!(flag & LOWUSED))
{
/* Change link of previous LOW-key */
gpos->data=ptr_to_rec;
gpos->next=(uint) (pos-data);
flag= (flag & HIGHFIND) | (LOWFIND | LOWUSED);
}
gpos=pos;
ptr_to_rec=pos->data;
}
}
else
{ /* key will be moved */
if (!(flag & HIGHFIND))
{
flag= (flag & LOWFIND) | HIGHFIND;
/* key shall be moved to the last (empty) position */
gpos2 = empty; empty=pos;
ptr_to_rec2=pos->data;
}
else
{
if (!(flag & HIGHUSED))
{
/* Change link of previous hash-key and save */
gpos2->data=ptr_to_rec2;
gpos2->next=(uint) (pos-data);
flag= (flag & LOWFIND) | (HIGHFIND | HIGHUSED);
}
gpos2=pos;
ptr_to_rec2=pos->data;
}
}
}
while ((idx=pos->next) != NO_RECORD);
if ((flag & (LOWFIND | LOWUSED)) == LOWFIND)
{
gpos->data=ptr_to_rec;
gpos->next=NO_RECORD;
}
if ((flag & (HIGHFIND | HIGHUSED)) == HIGHFIND)
{
gpos2->data=ptr_to_rec2;
gpos2->next=NO_RECORD;
}
}
/* Check if we are at the empty position */
idx=hash_mask(rec_hashnr(info,record),info->blength,info->records+1);
pos=data+idx;
if (pos == empty)
{
pos->data=(byte*) record;
pos->next=NO_RECORD;
}
else
{
/* Check if more records in same hash-nr family */
empty[0]=pos[0];
gpos=data+hash_rec_mask(info,pos,info->blength,info->records+1);
if (pos == gpos)
{
pos->data=(byte*) record;
pos->next=(uint) (empty - data);
}
else
{
pos->data=(byte*) record;
pos->next=NO_RECORD;
movelink(data,(uint) (pos-data),(uint) (gpos-data),(uint) (empty-data));
}
}
if (++info->records == info->blength)
info->blength+= info->blength;
return(0);
}
/******************************************************************************
** Remove one record from hash-table. The record with the same record
** ptr is removed.
** if there is a free-function it's called for record if found
******************************************************************************/
my_bool hash_delete(HASH *hash,byte *record)
{
uint blength,pos2,pos_hashnr,lastpos_hashnr,idx,empty_index;
HASH_LINK *data,*lastpos,*gpos,*pos,*pos3,*empty;
DBUG_ENTER("hash_delete");
if (!hash->records)
DBUG_RETURN(1);
blength=hash->blength;
data=dynamic_element(&hash->array,0,HASH_LINK*);
/* Search after record with key */
pos=data+ hash_mask(rec_hashnr(hash,record),blength,hash->records);
gpos = 0;
while (pos->data != record)
{
gpos=pos;
if (pos->next == NO_RECORD)
DBUG_RETURN(1); /* Key not found */
pos=data+pos->next;
}
if ( --(hash->records) < hash->blength >> 1) hash->blength>>=1;
lastpos=data+hash->records;
/* Remove link to record */
empty=pos; empty_index=(uint) (empty-data);
if (gpos)
gpos->next=pos->next; /* unlink current ptr */
else if (pos->next != NO_RECORD)
{
empty=data+(empty_index=pos->next);
pos->data=empty->data;
pos->next=empty->next;
}
if (empty == lastpos) /* last key at wrong pos or no next link */
goto exit;
/* Move the last key (lastpos) */
lastpos_hashnr=rec_hashnr(hash,lastpos->data);
/* pos is where lastpos should be */
pos=data+hash_mask(lastpos_hashnr,hash->blength,hash->records);
if (pos == empty) /* Move to empty position. */
{
empty[0]=lastpos[0];
goto exit;
}
pos_hashnr=rec_hashnr(hash,pos->data);
/* pos3 is where the pos should be */
pos3= data+hash_mask(pos_hashnr,hash->blength,hash->records);
if (pos != pos3)
{ /* pos is on wrong posit */
empty[0]=pos[0]; /* Save it here */
pos[0]=lastpos[0]; /* This should be here */
movelink(data,(uint) (pos-data),(uint) (pos3-data),empty_index);
goto exit;
}
pos2= hash_mask(lastpos_hashnr,blength,hash->records+1);
if (pos2 == hash_mask(pos_hashnr,blength,hash->records+1))
{ /* Identical key-positions */
if (pos2 != hash->records)
{
empty[0]=lastpos[0];
movelink(data,(uint) (lastpos-data),(uint) (pos-data),empty_index);
goto exit;
}
idx= (uint) (pos-data); /* Link pos->next after lastpos */
}
else idx= NO_RECORD; /* Different positions merge */
empty[0]=lastpos[0];
movelink(data,idx,empty_index,pos->next);
pos->next=empty_index;
exit:
VOID(pop_dynamic(&hash->array));
if (hash->free)
(*hash->free)((byte*) record);
DBUG_RETURN(0);
}
/*
Update keys when record has changed.
This is much more efficent than using a delete & insert.
*/
my_bool hash_update(HASH *hash,byte *record,byte *old_key,uint old_key_length)
{
uint idx,new_index,new_pos_index,blength,records,empty;
HASH_LINK org_link,*data,*previous,*pos;
DBUG_ENTER("hash_update");
data=dynamic_element(&hash->array,0,HASH_LINK*);
blength=hash->blength; records=hash->records;
/* Search after record with key */
idx=hash_mask(calc_hash(hash, old_key,(old_key_length ?
old_key_length :
hash->key_length)),
blength,records);
new_index=hash_mask(rec_hashnr(hash,record),blength,records);
if (idx == new_index)
DBUG_RETURN(0); /* Nothing to do (No record check) */
previous=0;
for (;;)
{
if ((pos= data+idx)->data == record)
break;
previous=pos;
if ((idx=pos->next) == NO_RECORD)
DBUG_RETURN(1); /* Not found in links */
}
org_link= *pos;
empty=idx;
/* Relink record from current chain */
if (!previous)
{
if (pos->next != NO_RECORD)
{
empty=pos->next;
*pos= data[pos->next];
}
}
else
previous->next=pos->next; /* unlink pos */
/* Move data to correct position */
pos=data+new_index;
new_pos_index=hash_rec_mask(hash,pos,blength,records);
if (new_index != new_pos_index)
{ /* Other record in wrong position */
data[empty] = *pos;
movelink(data,new_index,new_pos_index,empty);
org_link.next=NO_RECORD;
data[new_index]= org_link;
}
else
{ /* Link in chain at right position */
org_link.next=data[new_index].next;
data[empty]=org_link;
data[new_index].next=empty;
}
DBUG_RETURN(0);
}
byte *hash_element(HASH *hash,uint idx)
{
if (idx < hash->records)
return dynamic_element(&hash->array,idx,HASH_LINK*)->data;
return 0;
}
/*
Replace old row with new row. This should only be used when key
isn't changed
*/
void hash_replace(HASH *hash, HASH_SEARCH_STATE *current_record, byte *new_row)
{
if (*current_record != NO_RECORD) /* Safety */
dynamic_element(&hash->array, *current_record, HASH_LINK*)->data= new_row;
}
#ifndef DBUG_OFF
my_bool hash_check(HASH *hash)
{
int error;
uint i,rec_link,found,max_links,seek,links,idx;
uint records,blength;
HASH_LINK *data,*hash_info;
records=hash->records; blength=hash->blength;
data=dynamic_element(&hash->array,0,HASH_LINK*);
error=0;
for (i=found=max_links=seek=0 ; i < records ; i++)
{
if (hash_rec_mask(hash,data+i,blength,records) == i)
{
found++; seek++; links=1;
for (idx=data[i].next ;
idx != NO_RECORD && found < records + 1;
idx=hash_info->next)
{
if (idx >= records)
{
DBUG_PRINT("error",
("Found pointer outside array to %d from link starting at %d",
idx,i));
error=1;
}
hash_info=data+idx;
seek+= ++links;
if ((rec_link=hash_rec_mask(hash,hash_info,blength,records)) != i)
{
DBUG_PRINT("error",
("Record in wrong link at %d: Start %d Record: 0x%lx Record-link %d", idx,i,hash_info->data,rec_link));
error=1;
}
else
found++;
}
if (links > max_links) max_links=links;
}
}
if (found != records)
{
DBUG_PRINT("error",("Found %ld of %ld records"));
error=1;
}
if (records)
DBUG_PRINT("info",
("records: %ld seeks: %d max links: %d hitrate: %.2f",
records,seek,max_links,(float) seek / (float) records));
return error;
}
#endif
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