hash.c 15.6 KB
Newer Older
monty@hundin.mysql.fi's avatar
monty@hundin.mysql.fi committed
1 2 3 4 5 6 7 8
/* 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,
bk@work.mysql.com's avatar
bk@work.mysql.com committed
9
   but WITHOUT ANY WARRANTY; without even the implied warranty of
monty@hundin.mysql.fi's avatar
monty@hundin.mysql.fi committed
10 11 12 13 14 15
   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 */
bk@work.mysql.com's avatar
bk@work.mysql.com committed
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

/* 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

32 33 34 35 36
typedef struct st_hash_info {
  uint next;					/* index to next key */
  byte *data;					/* data for current entry */
} HASH_LINK;

bk@work.mysql.com's avatar
bk@work.mysql.com committed
37 38 39 40
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(HASH *hash,HASH_LINK *pos,const byte *key,uint length);

41 42 43
static uint calc_hash(HASH *hash,const byte *key,uint length)
{
  ulong nr1=1, nr2=4;
44
  hash->charset->coll->hash_sort(hash->charset,(uchar*) key,length,&nr1,&nr2);
45 46
  return nr1;
}
47

48
my_bool
monty@hundin.mysql.fi's avatar
merge  
monty@hundin.mysql.fi committed
49
_hash_init(HASH *hash,CHARSET_INFO *charset,
50 51 52
	   uint size,uint key_offset,uint key_length,
	   hash_get_key get_key,
	   void (*free_element)(void*),uint flags CALLER_INFO_PROTO)
bk@work.mysql.com's avatar
bk@work.mysql.com committed
53 54
{
  DBUG_ENTER("hash_init");
55
  DBUG_PRINT("enter",("hash: 0x%lx  size: %d",hash,size));
bk@work.mysql.com's avatar
bk@work.mysql.com committed
56 57

  hash->records=0;
58
  if (my_init_dynamic_array_ci(&hash->array,sizeof(HASH_LINK),size,0))
bk@work.mysql.com's avatar
bk@work.mysql.com committed
59 60
  {
    hash->free=0;				/* Allow call to hash_free */
61
    DBUG_RETURN(1);
bk@work.mysql.com's avatar
bk@work.mysql.com committed
62 63 64 65 66 67 68 69
  }
  hash->key_offset=key_offset;
  hash->key_length=key_length;
  hash->blength=1;
  hash->current_record= NO_RECORD;		/* For the future */
  hash->get_key=get_key;
  hash->free=free_element;
  hash->flags=flags;
70
  hash->charset=charset;
bk@work.mysql.com's avatar
bk@work.mysql.com committed
71 72 73 74
  DBUG_RETURN(0);
}


75 76 77 78 79 80 81 82 83 84 85
/*
  Call hash->free on all elements in hash.

  SYNOPSIS
    hash_free_elements()
    hash   hash table

  NOTES:
    Sets records to 0
*/

86
static inline void hash_free_elements(HASH *hash)
bk@work.mysql.com's avatar
bk@work.mysql.com committed
87 88 89 90
{
  if (hash->free)
  {
    HASH_LINK *data=dynamic_element(&hash->array,0,HASH_LINK*);
91 92 93
    HASH_LINK *end= data + hash->records;
    while (data < end)
      (*hash->free)((data++)->data);
bk@work.mysql.com's avatar
bk@work.mysql.com committed
94 95
  }
  hash->records=0;
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116
}


/*
  Free memory used by hash.

  SYNOPSIS
    hash_free()
    hash   the hash to delete elements of

  NOTES: Hash can't be reused wuthing calling hash_init again.
*/

void hash_free(HASH *hash)
{
  DBUG_ENTER("hash_free");
  DBUG_PRINT("enter",("hash: 0x%lxd",hash));

  hash_free_elements(hash);
  hash->free= 0;
  delete_dynamic(&hash->array);
bk@work.mysql.com's avatar
bk@work.mysql.com committed
117 118 119
  DBUG_VOID_RETURN;
}

120 121 122 123 124 125

/*
  Delete all elements from the hash (the hash itself is to be reused).

  SYNOPSIS
    hash_reset()
126
    hash   the hash to delete elements of
127 128 129 130 131
*/

void hash_reset(HASH *hash)
{
  DBUG_ENTER("hash_reset");
132 133 134
  DBUG_PRINT("enter",("hash: 0x%lxd",hash));

  hash_free_elements(hash);
135
  reset_dynamic(&hash->array);
136
  /* Set row pointers so that the hash can be reused at once */
137 138 139 140 141
  hash->blength= 1;
  hash->current_record= NO_RECORD;
  DBUG_VOID_RETURN;
}

bk@work.mysql.com's avatar
bk@work.mysql.com committed
142 143
	/* some helper functions */

144 145 146 147 148 149
/*
  This function is char* instead of byte* as HPUX11 compiler can't
  handle inline functions that are not defined as native types
*/

inline char*
bk@work.mysql.com's avatar
bk@work.mysql.com committed
150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169
hash_key(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(HASH *hash,HASH_LINK *pos,uint buffmax,
			  uint maxlength)
{
  uint length;
170
  byte *key= (byte*) hash_key(hash,pos->data,&length,0);
171
  return hash_mask(calc_hash(hash,key,length),buffmax,maxlength);
bk@work.mysql.com's avatar
bk@work.mysql.com committed
172 173
}

174

bk@work.mysql.com's avatar
bk@work.mysql.com committed
175

lenz@mysql.com's avatar
lenz@mysql.com committed
176 177
/* for compilers which can not handle inline */
#if !defined(__SUNPRO_C) && !defined(__USLC__) && !defined(__sgi)
178 179
inline
#endif
180
unsigned int rec_hashnr(HASH *hash,const byte *record)
bk@work.mysql.com's avatar
bk@work.mysql.com committed
181 182
{
  uint length;
183
  byte *key= (byte*) hash_key(hash,record,&length,0);
184
  return calc_hash(hash,key,length);
bk@work.mysql.com's avatar
bk@work.mysql.com committed
185 186 187 188 189 190 191 192 193 194 195 196 197 198 199
}


	/* Search after a record based on a key */
	/* Sets info->current_ptr to found record */

gptr hash_search(HASH *hash,const byte *key,uint length)
{
  HASH_LINK *pos;
  uint flag,idx;
  DBUG_ENTER("hash_search");

  flag=1;
  if (hash->records)
  {
200
    idx=hash_mask(calc_hash(hash,key,length ? length : hash->key_length),
bk@work.mysql.com's avatar
bk@work.mysql.com committed
201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268
		    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));
	hash->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);
  }
  hash->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(HASH *hash,const byte *key,uint length)
{
  HASH_LINK *pos;
  uint idx;

  if (hash->current_record != NO_RECORD)
  {
    HASH_LINK *data=dynamic_element(&hash->array,0,HASH_LINK*);
    for (idx=data[hash->current_record].next; idx != NO_RECORD ; idx=pos->next)
    {
      pos=data+idx;
      if (!hashcmp(hash,pos,key,length))
      {
	hash->current_record= idx;
	return pos->data;
      }
    }
    hash->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 */

static int hashcmp(HASH *hash,HASH_LINK *pos,const byte *key,uint length)
{
  uint rec_keylength;
269
  byte *rec_key= (byte*) hash_key(hash,pos->data,&rec_keylength,1);
270 271 272
  return ((length && length != rec_keylength) ||
	  my_strnncoll(hash->charset, (uchar*) rec_key, rec_keylength,
		       (uchar*) key, length));
bk@work.mysql.com's avatar
bk@work.mysql.com committed
273 274 275 276 277
}


	/* Write a hash-key to the hash-index */

hf@deer.(none)'s avatar
SCRUM  
hf@deer.(none) committed
278
my_bool my_hash_insert(HASH *info,const byte *record)
bk@work.mysql.com's avatar
bk@work.mysql.com committed
279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416
{
  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 */

  info->current_record= NO_RECORD;
  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");
417 418
  if (!hash->records)
    DBUG_RETURN(1);
bk@work.mysql.com's avatar
bk@work.mysql.com committed
419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510

  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;
  hash->current_record= NO_RECORD;
  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 */

511
  idx=hash_mask(calc_hash(hash, old_key,(old_key_length ?
monty@hundin.mysql.fi's avatar
monty@hundin.mysql.fi committed
512 513
					      old_key_length :
					      hash->key_length)),
bk@work.mysql.com's avatar
bk@work.mysql.com committed
514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572
		  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 */
  }
  hash->current_record= NO_RECORD;
  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;
}


monty@hundin.mysql.fi's avatar
monty@hundin.mysql.fi committed
573 574 575 576 577 578 579
/*
  Replace old row with new row.  This should only be used when key
  isn't changed
*/

void hash_replace(HASH *hash, uint idx, byte *new_row)
{
580 581
  if (idx != NO_RECORD)				/* Safety */
    dynamic_element(&hash->array,idx,HASH_LINK*)->data=new_row;
monty@hundin.mysql.fi's avatar
monty@hundin.mysql.fi committed
582 583 584
}


bk@work.mysql.com's avatar
bk@work.mysql.com committed
585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618
#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",
619
		     ("Record in wrong link at %d: Start %d  Record: 0x%lx  Record-link %d", idx,i,hash_info->data,rec_link));
bk@work.mysql.com's avatar
bk@work.mysql.com committed
620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639
	  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