diff options
Diffstat (limited to 'mysys/lf_hash.cc')
| -rw-r--r-- | mysys/lf_hash.cc | 587 |
1 files changed, 587 insertions, 0 deletions
diff --git a/mysys/lf_hash.cc b/mysys/lf_hash.cc new file mode 100644 index 00000000..bc3504bc --- /dev/null +++ b/mysys/lf_hash.cc @@ -0,0 +1,587 @@ +/* Copyright (c) 2006, 2018, Oracle and/or its affiliates. + Copyright (c) 2009, 2020, MariaDB + + 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 */ + +/* + extensible hash + + TODO + try to get rid of dummy nodes ? + for non-unique hash, count only _distinct_ values + (but how to do it in lf_hash_delete ?) +*/ +#include "mysys_priv.h" +#include <m_string.h> +#include <mysys_err.h> +#include <my_bit.h> +#include <lf.h> +#include "my_cpu.h" +#include "assume_aligned.h" + +/* An element of the list */ +typedef struct { + intptr link; /* a pointer to the next element in a list and a flag */ + const uchar *key; + size_t keylen; + uint32 hashnr; /* reversed hash number, for sorting */ + /* + data is stored here, directly after the keylen. + thus the pointer to data is (void*)(slist_element_ptr+1) + */ +} LF_SLIST; + +const int LF_HASH_OVERHEAD= sizeof(LF_SLIST); + +/* + a structure to pass the context (pointers two the three successive elements + in a list) from l_find to l_insert/l_delete +*/ +typedef struct { + intptr *prev; + LF_SLIST *curr, *next; +} CURSOR; + +/* + the last bit in LF_SLIST::link is a "deleted" flag. + the helper macros below convert it to a pure pointer or a pure flag +*/ +#define PTR(V) (LF_SLIST *)((V) & (~(intptr)1)) +#define DELETED(V) ((V) & 1) + +/** walk the list, searching for an element or invoking a callback + + Search for hashnr/key/keylen in the list starting from 'head' and + position the cursor. The list is ORDER BY hashnr, key + + @param head start walking the list from this node + @param cs charset for comparing keys, NULL if callback is used + @param hashnr hash number to search for + @param key key to search for OR data for the callback + @param keylen length of the key to compare, 0 if callback is used + @param cursor for returning the found element + @param pins see lf_alloc-pin.c + @param callback callback action, invoked for every element + + @note + cursor is positioned in either case + pins[0..2] are used, they are NOT removed on return + callback might see some elements twice (because of retries) + + @return + if find: 0 - not found + 1 - found + if callback: + 0 - ok + 1 - error (callbck returned 1) +*/ +static int l_find(LF_SLIST **head, CHARSET_INFO *cs, uint32 hashnr, + const uchar *key, size_t keylen, CURSOR *cursor, LF_PINS *pins, + my_hash_walk_action callback) +{ + uint32 cur_hashnr; + const uchar *cur_key; + size_t cur_keylen; + intptr link; + + DBUG_ASSERT(!cs || !callback); /* should not be set both */ + DBUG_ASSERT(!keylen || !callback); /* should not be set both */ + +retry: + cursor->prev= (intptr *) my_assume_aligned<sizeof(intptr)>(head); + do { /* PTR() isn't necessary below, head is a dummy node */ + cursor->curr= my_assume_aligned<sizeof(LF_SLIST *)>((LF_SLIST *)(*cursor->prev)); + lf_pin(pins, 1, cursor->curr); + } while (my_atomic_loadptr((void **)my_assume_aligned<sizeof(LF_SLIST *)>(cursor->prev)) != cursor->curr && + LF_BACKOFF()); + for (;;) + { + if (unlikely(!cursor->curr)) + return 0; /* end of the list */ + + cur_hashnr= cursor->curr->hashnr; + cur_keylen= cursor->curr->keylen; + /* The key element needs to be aligned, not necessary what it points to */ + my_assume_aligned<sizeof(const uchar *)>(&cursor->curr->key); + cur_key= cursor->curr->key; + + do { + /* attempting to my_assume_aligned onlink below broke the implementation */ + link= cursor->curr->link; + cursor->next= my_assume_aligned<sizeof(LF_SLIST *)>(PTR(link)); + lf_pin(pins, 0, cursor->next); + } while (link != cursor->curr->link && LF_BACKOFF()); + + if (!DELETED(link)) + { + if (unlikely(callback)) + { + if (cur_hashnr & 1 && callback(cursor->curr + 1, (void*)key)) + return 1; + } + else if (cur_hashnr >= hashnr) + { + int r= 1; + if (cur_hashnr > hashnr || + (r= my_strnncoll(cs, cur_key, cur_keylen, key, keylen)) >= 0) + return !r; + } + cursor->prev= &(cursor->curr->link); + if (!(cur_hashnr & 1)) /* dummy node */ + head= (LF_SLIST **)cursor->prev; + lf_pin(pins, 2, cursor->curr); + } + else + { + /* + we found a deleted node - be nice, help the other thread + and remove this deleted node + */ + if (my_atomic_casptr((void **) cursor->prev, + (void **) &cursor->curr, cursor->next) && LF_BACKOFF()) + lf_alloc_free(pins, cursor->curr); + else + goto retry; + } + cursor->curr= cursor->next; + lf_pin(pins, 1, cursor->curr); + } +} + + +/* static l_find is the only user my_assume_aligned, keep the rest as c scoped */ +C_MODE_START + +/* + DESCRIPTION + insert a 'node' in the list that starts from 'head' in the correct + position (as found by l_find) + + RETURN + 0 - inserted + not 0 - a pointer to a duplicate (not pinned and thus unusable) + + NOTE + it uses pins[0..2], on return all pins are removed. + if there're nodes with the same key value, a new node is added before them. +*/ +static LF_SLIST *l_insert(LF_SLIST **head, CHARSET_INFO *cs, + LF_SLIST *node, LF_PINS *pins, uint flags) +{ + CURSOR cursor; + int res; + + for (;;) + { + if (l_find(head, cs, node->hashnr, node->key, node->keylen, + &cursor, pins, 0) && + (flags & LF_HASH_UNIQUE)) + { + res= 0; /* duplicate found */ + break; + } + else + { + node->link= (intptr)cursor.curr; + DBUG_ASSERT(node->link != (intptr)node); /* no circular references */ + DBUG_ASSERT(cursor.prev != &node->link); /* no circular references */ + if (my_atomic_casptr((void **) cursor.prev, + (void **)(char*) &cursor.curr, node)) + { + res= 1; /* inserted ok */ + break; + } + } + } + lf_unpin(pins, 0); + lf_unpin(pins, 1); + lf_unpin(pins, 2); + /* + Note that cursor.curr is not pinned here and the pointer is unreliable, + the object may disappear anytime. But if it points to a dummy node, the + pointer is safe, because dummy nodes are never freed - initialize_bucket() + uses this fact. + */ + return res ? 0 : cursor.curr; +} + +/* + DESCRIPTION + deletes a node as identified by hashnr/keey/keylen from the list + that starts from 'head' + + RETURN + 0 - ok + 1 - not found + + NOTE + it uses pins[0..2], on return all pins are removed. +*/ +static int l_delete(LF_SLIST **head, CHARSET_INFO *cs, uint32 hashnr, + const uchar *key, uint keylen, LF_PINS *pins) +{ + CURSOR cursor; + int res; + + for (;;) + { + if (!l_find(head, cs, hashnr, key, keylen, &cursor, pins, 0)) + { + res= 1; /* not found */ + break; + } + else + { + /* mark the node deleted */ + if (my_atomic_casptr((void **) (char*) &(cursor.curr->link), + (void **) (char*) &cursor.next, + (void *)(((intptr)cursor.next) | 1))) + { + /* and remove it from the list */ + if (my_atomic_casptr((void **)cursor.prev, + (void **)(char*)&cursor.curr, cursor.next)) + lf_alloc_free(pins, cursor.curr); + else + { + /* + somebody already "helped" us and removed the node ? + Let's check if we need to help that someone too! + (to ensure the number of "set DELETED flag" actions + is equal to the number of "remove from the list" actions) + */ + l_find(head, cs, hashnr, key, keylen, &cursor, pins, 0); + } + res= 0; + break; + } + } + } + lf_unpin(pins, 0); + lf_unpin(pins, 1); + lf_unpin(pins, 2); + return res; +} + +/* + DESCRIPTION + searches for a node as identified by hashnr/keey/keylen in the list + that starts from 'head' + + RETURN + 0 - not found + node - found + + NOTE + it uses pins[0..2], on return the pin[2] keeps the node found + all other pins are removed. +*/ +static LF_SLIST *l_search(LF_SLIST **head, CHARSET_INFO *cs, + uint32 hashnr, const uchar *key, uint keylen, + LF_PINS *pins) +{ + CURSOR cursor; + int res= l_find(head, cs, hashnr, key, keylen, &cursor, pins, 0); + if (res) + lf_pin(pins, 2, cursor.curr); + else + lf_unpin(pins, 2); + lf_unpin(pins, 1); + lf_unpin(pins, 0); + return res ? cursor.curr : 0; +} + +static inline const uchar* hash_key(const LF_HASH *hash, + const uchar *record, size_t *length) +{ + if (hash->get_key) + return (*hash->get_key)(record, length, 0); + *length= hash->key_length; + return record + hash->key_offset; +} + +/* + Compute the hash key value from the raw key. + + @note, that the hash value is limited to 2^31, because we need one + bit to distinguish between normal and dummy nodes. +*/ +static inline my_hash_value_type calc_hash(CHARSET_INFO *cs, + const uchar *key, + size_t keylen) +{ + ulong nr1= 1, nr2= 4; + my_ci_hash_sort(cs, (uchar*) key, keylen, &nr1, &nr2); + return nr1; +} + +#define MAX_LOAD 1.0 /* average number of elements in a bucket */ + +static int initialize_bucket(LF_HASH *, LF_SLIST **, uint, LF_PINS *); + +static void default_initializer(LF_HASH *hash, void *dst, const void *src) +{ + memcpy(dst, src, hash->element_size); +} + + +/* + Initializes lf_hash, the arguments are compatible with hash_init + + @note element_size sets both the size of allocated memory block for + lf_alloc and a size of memcpy'ed block size in lf_hash_insert. Typically + they are the same, indeed. But LF_HASH::element_size can be decreased + after lf_hash_init, and then lf_alloc will allocate larger block that + lf_hash_insert will copy over. It is desirable if part of the element + is expensive to initialize - for example if there is a mutex or + DYNAMIC_ARRAY. In this case they should be initialize in the + LF_ALLOCATOR::constructor, and lf_hash_insert should not overwrite them. + + The above works well with PODS. For more complex cases (e.g. C++ classes + with private members) use initializer function. +*/ +void lf_hash_init(LF_HASH *hash, uint element_size, uint flags, + uint key_offset, uint key_length, my_hash_get_key get_key, + CHARSET_INFO *charset) +{ + lf_alloc_init(&hash->alloc, sizeof(LF_SLIST)+element_size, + offsetof(LF_SLIST, key)); + lf_dynarray_init(&hash->array, sizeof(LF_SLIST *)); + hash->size= 1; + hash->count= 0; + hash->element_size= element_size; + hash->flags= flags; + hash->charset= charset ? charset : &my_charset_bin; + hash->key_offset= key_offset; + hash->key_length= key_length; + hash->get_key= get_key; + hash->initializer= default_initializer; + hash->hash_function= calc_hash; + DBUG_ASSERT(get_key ? !key_offset && !key_length : key_length); +} + +void lf_hash_destroy(LF_HASH *hash) +{ + LF_SLIST *el, **head= (LF_SLIST **)lf_dynarray_value(&hash->array, 0); + + if (head) + { + el= *head; + while (el) + { + intptr next= el->link; + if (el->hashnr & 1) + lf_alloc_direct_free(&hash->alloc, el); /* normal node */ + else + my_free(el); /* dummy node */ + el= (LF_SLIST *)next; + } + } + lf_alloc_destroy(&hash->alloc); + lf_dynarray_destroy(&hash->array); +} + +/* + DESCRIPTION + inserts a new element to a hash. it will have a _copy_ of + data, not a pointer to it. + + RETURN + 0 - inserted + 1 - didn't (unique key conflict) + -1 - out of memory + + NOTE + see l_insert() for pin usage notes +*/ +int lf_hash_insert(LF_HASH *hash, LF_PINS *pins, const void *data) +{ + int csize, bucket, hashnr; + LF_SLIST *node, **el; + + node= (LF_SLIST *)lf_alloc_new(pins); + if (unlikely(!node)) + return -1; + hash->initializer(hash, node + 1, data); + node->key= hash_key(hash, (uchar *)(node+1), &node->keylen); + hashnr= hash->hash_function(hash->charset, node->key, node->keylen) & INT_MAX32; + bucket= hashnr % hash->size; + el= (LF_SLIST **)lf_dynarray_lvalue(&hash->array, bucket); + if (unlikely(!el)) + return -1; + if (*el == NULL && unlikely(initialize_bucket(hash, el, bucket, pins))) + return -1; + node->hashnr= my_reverse_bits(hashnr) | 1; /* normal node */ + if (l_insert(el, hash->charset, node, pins, hash->flags)) + { + lf_alloc_free(pins, node); + return 1; + } + csize= hash->size; + if ((my_atomic_add32(&hash->count, 1)+1.0) / csize > MAX_LOAD) + my_atomic_cas32(&hash->size, &csize, csize*2); + return 0; +} + +/* + DESCRIPTION + deletes an element with the given key from the hash (if a hash is + not unique and there're many elements with this key - the "first" + matching element is deleted) + RETURN + 0 - deleted + 1 - didn't (not found) + NOTE + see l_delete() for pin usage notes +*/ +int lf_hash_delete(LF_HASH *hash, LF_PINS *pins, const void *key, uint keylen) +{ + LF_SLIST **el; + uint bucket, hashnr; + + hashnr= hash->hash_function(hash->charset, (uchar *)key, keylen) & INT_MAX32; + + /* hide OOM errors - if we cannot initialize a bucket, try the previous one */ + for (bucket= hashnr % hash->size; ;bucket= my_clear_highest_bit(bucket)) + { + el= (LF_SLIST **)lf_dynarray_lvalue(&hash->array, bucket); + if (el && (*el || initialize_bucket(hash, el, bucket, pins) == 0)) + break; + if (unlikely(bucket == 0)) + return 1; /* if there's no bucket==0, the hash is empty */ + } + if (l_delete(el, hash->charset, my_reverse_bits(hashnr) | 1, + (uchar *)key, keylen, pins)) + { + return 1; + } + my_atomic_add32(&hash->count, -1); + return 0; +} + +/* + RETURN + a pointer to an element with the given key (if a hash is not unique and + there're many elements with this key - the "first" matching element) + NULL if nothing is found + + NOTE + see l_search() for pin usage notes +*/ +void *lf_hash_search_using_hash_value(LF_HASH *hash, LF_PINS *pins, + my_hash_value_type hashnr, + const void *key, uint keylen) +{ + LF_SLIST **el, *found; + uint bucket; + + /* hide OOM errors - if we cannot initialize a bucket, try the previous one */ + for (bucket= hashnr % hash->size; ;bucket= my_clear_highest_bit(bucket)) + { + el= (LF_SLIST **)lf_dynarray_lvalue(&hash->array, bucket); + if (el && (*el || initialize_bucket(hash, el, bucket, pins) == 0)) + break; + if (unlikely(bucket == 0)) + return 0; /* if there's no bucket==0, the hash is empty */ + } + found= l_search(el, hash->charset, my_reverse_bits(hashnr) | 1, + (uchar *)key, keylen, pins); + return found ? found+1 : 0; +} + + +/** + Iterate over all elements in hash and call function with the element + + @note + If one of 'action' invocations returns 1 the iteration aborts. + 'action' might see some elements twice! + + @retval 0 ok + @retval 1 error (action returned 1) +*/ +int lf_hash_iterate(LF_HASH *hash, LF_PINS *pins, + my_hash_walk_action action, void *argument) +{ + CURSOR cursor; + uint bucket= 0; + int res; + LF_SLIST **el; + + el= (LF_SLIST **)lf_dynarray_lvalue(&hash->array, bucket); + if (unlikely(!el)) + return 0; /* if there's no bucket==0, the hash is empty */ + if (*el == NULL && unlikely(initialize_bucket(hash, el, bucket, pins))) + return 0; /* if there's no bucket==0, the hash is empty */ + + res= l_find(el, 0, 0, (uchar*)argument, 0, &cursor, pins, action); + + lf_unpin(pins, 2); + lf_unpin(pins, 1); + lf_unpin(pins, 0); + return res; +} + +void *lf_hash_search(LF_HASH *hash, LF_PINS *pins, const void *key, uint keylen) +{ + return lf_hash_search_using_hash_value(hash, pins, + hash->hash_function(hash->charset, + (uchar*) key, + keylen) & INT_MAX32, + key, keylen); +} + +static const uchar *dummy_key= (uchar*)""; + +/* + RETURN + 0 - ok + -1 - out of memory +*/ +static int initialize_bucket(LF_HASH *hash, LF_SLIST **node, + uint bucket, LF_PINS *pins) +{ + uint parent= my_clear_highest_bit(bucket); + LF_SLIST *dummy= (LF_SLIST *)my_malloc(key_memory_lf_slist, + sizeof(LF_SLIST), MYF(MY_WME)); + LF_SLIST **tmp= 0, *cur; + LF_SLIST **el= (LF_SLIST **)lf_dynarray_lvalue(&hash->array, parent); + if (unlikely(!el || !dummy)) + return -1; + if (*el == NULL && bucket && + unlikely(initialize_bucket(hash, el, parent, pins))) + { + my_free(dummy); + return -1; + } + dummy->hashnr= my_reverse_bits(bucket) | 0; /* dummy node */ + dummy->key= dummy_key; + dummy->keylen= 0; + if ((cur= l_insert(el, hash->charset, dummy, pins, LF_HASH_UNIQUE))) + { + my_free(dummy); + dummy= cur; + } + my_atomic_casptr((void **)node, (void **)(char*) &tmp, dummy); + /* + note that if the CAS above failed (after l_insert() succeeded), + it would mean that some other thread has executed l_insert() for + the same dummy node, its l_insert() failed, it picked up our + dummy node (in "dummy= cur") and executed the same CAS as above. + Which means that even if CAS above failed we don't need to retry, + and we should not free(dummy) - there's no memory leak here + */ + return 0; +} + +C_MODE_END |