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-rw-r--r--mysys/lf_hash.cc587
1 files changed, 587 insertions, 0 deletions
diff --git a/mysys/lf_hash.cc b/mysys/lf_hash.cc
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+++ b/mysys/lf_hash.cc
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+/* 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