* tables of power of two in size are used, collisions are handled by
* chaining. See the source code for more information... :)
*
- * Copyright (c) 2006-20
09, Salvatore Sanfilippo <antirez at gmail dot com>
+ * Copyright (c) 2006-20
10, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
#include <stdarg.h>
#include <assert.h>
#include <limits.h>
+#include <sys/time.h>
#include "dict.h"
#include "zmalloc.h"
+/* Using dictEnableResize() / dictDisableResize() we make possible to
+ * enable/disable resizing of the hash table as needed. This is very important
+ * for Redis, as we use copy-on-write and don't want to move too much memory
+ * around when there is a child performing saving operations. */
+static int dict_can_resize = 1;
+
/* ---------------------------- Utility funcitons --------------------------- */
static void _dictPanic(const char *fmt, ...)
/* Reset an hashtable already initialized with ht_init().
* NOTE: This function should only called by ht_destroy(). */
-static void _dictReset(dict *ht)
+static void _dictReset(dictht *ht)
{
ht->table = NULL;
ht->size = 0;
dict *dictCreate(dictType *type,
void *privDataPtr)
{
- dict *ht = _dictAlloc(sizeof(*ht));
+ dict *d = _dictAlloc(sizeof(*d));
- _dictInit(ht,type,privDataPtr);
- return ht;
+ _dictInit(d,type,privDataPtr);
+ return d;
}
/* Initialize the hash table */
-int _dictInit(dict *ht, dictType *type,
+int _dictInit(dict *d, dictType *type,
void *privDataPtr)
{
- _dictReset(ht);
- ht->type = type;
- ht->privdata = privDataPtr;
+ _dictReset(&d->ht[0]);
+ _dictReset(&d->ht[1]);
+ d->type = type;
+ d->privdata = privDataPtr;
+ d->rehashidx = -1;
+ d->iterators = 0;
return DICT_OK;
}
/* Resize the table to the minimal size that contains all the elements,
* but with the invariant of a USER/BUCKETS ration near to <= 1 */
-int dictResize(dict *ht)
+int dictResize(dict *d)
{
- int minimal = ht->used;
+ int minimal;
+ if (!dict_can_resize || dictIsRehashing(d)) return DICT_ERR;
+ minimal = d->ht[0].used;
if (minimal < DICT_HT_INITIAL_SIZE)
minimal = DICT_HT_INITIAL_SIZE;
- return dictExpand(ht, minimal);
+ return dictExpand(d, minimal);
}
/* Expand or create the hashtable */
-int dictExpand(dict *ht, unsigned long size)
+int dictExpand(dict *d, unsigned long size)
{
- dict n; /* the new hashtable */
- unsigned long realsize = _dictNextPower(size), i;
+ dictht n; /* the new hashtable */
+ unsigned long realsize = _dictNextPower(size);
/* the size is invalid if it is smaller than the number of
* elements already inside the hashtable */
- if (ht->used > size)
+ if (dictIsRehashing(d) || d->ht[0].used > size)
return DICT_ERR;
- _dictInit(&n, ht->type, ht->privdata);
n.size = realsize;
n.sizemask = realsize-1;
n.table = _dictAlloc(realsize*sizeof(dictEntry*));
+ n.used = 0;
/* Initialize all the pointers to NULL */
memset(n.table, 0, realsize*sizeof(dictEntry*));
- /* Copy all the elements from the old to the new table:
- * note that if the old hash table is empty ht->size is zero,
- * so dictExpand just creates an hash table. */
- n.used = ht->used;
- for (i = 0; i < ht->size && ht->used > 0; i++) {
- dictEntry *he, *nextHe;
+ /* Is this the first initialization? If so it's not really a rehashing
+ * we just set the first hash table so that it can accept keys. */
+ if (d->ht[0].table == NULL) {
+ d->ht[0] = n;
+ return DICT_OK;
+ }
- if (ht->table[i] == NULL) continue;
-
- /* For each hash entry on this slot... */
- he = ht->table[i];
- while(he) {
+ /* Prepare a second hash table for incremental rehashing */
+ d->ht[1] = n;
+ d->rehashidx = 0;
+ return DICT_OK;
+}
+
+/* Performs N steps of incremental rehashing. Returns 1 if there are still
+ * keys to move from the old to the new hash table, otherwise 0 is returned.
+ * Note that a rehashing step consists in moving a bucket (that may have more
+ * thank one key as we use chaining) from the old to the new hash table. */
+int dictRehash(dict *d, int n) {
+ if (!dictIsRehashing(d)) return 0;
+
+ while(n--) {
+ dictEntry *de, *nextde;
+
+ /* Check if we already rehashed the whole table... */
+ if (d->ht[0].used == 0) {
+ _dictFree(d->ht[0].table);
+ d->ht[0] = d->ht[1];
+ _dictReset(&d->ht[1]);
+ d->rehashidx = -1;
+ return 0;
+ }
+
+ /* Note that rehashidx can't overflow as we are sure there are more
+ * elements because ht[0].used != 0 */
+ while(d->ht[0].table[d->rehashidx] == NULL) d->rehashidx++;
+ de = d->ht[0].table[d->rehashidx];
+ /* Move all the keys in this bucket from the old to the new hash HT */
+ while(de) {
unsigned int h;
- nextHe = he->next;
- /* Get the new element index */
- h = dictHashKey(ht, he->key) & n.sizemask;
- he->next = n.table[h];
- n.table[h] = he;
- ht->used--;
- /* Pass to the next element */
- he = nextHe;
+ nextde = de->next;
+ /* Get the index in the new hash table */
+ h = dictHashKey(d, de->key) & d->ht[1].sizemask;
+ de->next = d->ht[1].table[h];
+ d->ht[1].table[h] = de;
+ d->ht[0].used--;
+ d->ht[1].used++;
+ de = nextde;
}
+ d->ht[0].table[d->rehashidx] = NULL;
+ d->rehashidx++;
}
- assert(ht->used == 0);
- _dictFree(ht->table);
+ return 1;
+}
- /* Remap the new hashtable in the old */
- *ht = n;
- return DICT_OK;
+long long timeInMilliseconds(void) {
+ struct timeval tv;
+
+ gettimeofday(&tv,NULL);
+ return (((long long)tv.tv_sec)*1000)+(tv.tv_usec/1000);
+}
+
+/* Rehash for an amount of time between ms milliseconds and ms+1 milliseconds */
+int dictRehashMilliseconds(dict *d, int ms) {
+ long long start = timeInMilliseconds();
+ int rehashes = 0;
+
+ while(dictRehash(d,100)) {
+ rehashes += 100;
+ if (timeInMilliseconds()-start > ms) break;
+ }
+ return rehashes;
+}
+
+/* This function performs just a step of rehashing, and only if there are
+ * not iterators bound to our hash table. When we have iterators in the middle
+ * of a rehashing we can't mess with the two hash tables otherwise some element
+ * can be missed or duplicated.
+ *
+ * This function is called by common lookup or update operations in the
+ * dictionary so that the hash table automatically migrates from H1 to H2
+ * while it is actively used. */
+static void _dictRehashStep(dict *d) {
+ if (d->iterators == 0) dictRehash(d,1);
}
/* Add an element to the target hash table */
-int dictAdd(dict *ht, void *key, void *val)
+int dictAdd(dict *d, void *key, void *val)
{
int index;
dictEntry *entry;
+ dictht *ht;
+
+ if (dictIsRehashing(d)) _dictRehashStep(d);
/* Get the index of the new element, or -1 if
* the element already exists. */
- if ((index = _dictKeyIndex(ht, key)) == -1)
+ if ((index = _dictKeyIndex(d, key)) == -1)
return DICT_ERR;
/* Allocates the memory and stores key */
+ ht = dictIsRehashing(d) ? &d->ht[1] : &d->ht[0];
entry = _dictAlloc(sizeof(*entry));
entry->next = ht->table[index];
ht->table[index] = entry;
+ ht->used++;
/* Set the hash entry fields. */
- dictSetHashKey(ht, entry, key);
- dictSetHashVal(ht, entry, val);
- ht->used++;
+ dictSetHashKey(d, entry, key);
+ dictSetHashVal(d, entry, val);
return DICT_OK;
}
-/* Add an element, discarding the old if the key already exists */
-int dictReplace(dict *ht, void *key, void *val)
+/* Add an element, discarding the old if the key already exists.
+ * Return 1 if the key was added from scratch, 0 if there was already an
+ * element with such key and dictReplace() just performed a value update
+ * operation. */
+int dictReplace(dict *d, void *key, void *val)
{
- dictEntry *entry;
+ dictEntry *entry, auxentry;
/* Try to add the element. If the key
* does not exists dictAdd will suceed. */
- if (dictAdd(ht, key, val) == DICT_OK)
- return DICT_OK;
+ if (dictAdd(d, key, val) == DICT_OK)
+ return 1;
/* It already exists, get the entry */
- entry = dictFind(ht, key);
+ entry = dictFind(d, key);
/* Free the old value and set the new one */
- dictFreeEntryVal(ht, entry);
- dictSetHashVal(ht, entry, val);
- return DICT_OK;
+ /* Set the new value and free the old one. Note that it is important
+ * to do that in this order, as the value may just be exactly the same
+ * as the previous one. In this context, think to reference counting,
+ * you want to increment (set), and then decrement (free), and not the
+ * reverse. */
+ auxentry = *entry;
+ dictSetHashVal(d, entry, val);
+ dictFreeEntryVal(d, &auxentry);
+ return 0;
}
/* Search and remove an element */
-static int dictGenericDelete(dict *ht, const void *key, int nofree)
+static int dictGenericDelete(dict *d, const void *key, int nofree)
{
- unsigned int h;
+ unsigned int h, idx;
dictEntry *he, *prevHe;
+ int table;
- if (ht->size == 0)
- return DICT_ERR;
- h = dictHashKey(ht, key) & ht->sizemask;
- he = ht->table[h];
+ if (d->ht[0].size == 0) return DICT_ERR; /* d->ht[0].table is NULL */
+ if (dictIsRehashing(d)) _dictRehashStep(d);
+ h = dictHashKey(d, key);
- prevHe = NULL;
- while(he) {
- if (dictCompareHashKeys(ht, key, he->key)) {
- /* Unlink the element from the list */
- if (prevHe)
- prevHe->next = he->next;
- else
- ht->table[h] = he->next;
- if (!nofree) {
- dictFreeEntryKey(ht, he);
- dictFreeEntryVal(ht, he);
+ for (table = 0; table <= 1; table++) {
+ idx = h & d->ht[table].sizemask;
+ he = d->ht[table].table[idx];
+ prevHe = NULL;
+ while(he) {
+ if (dictCompareHashKeys(d, key, he->key)) {
+ /* Unlink the element from the list */
+ if (prevHe)
+ prevHe->next = he->next;
+ else
+ d->ht[table].table[idx] = he->next;
+ if (!nofree) {
+ dictFreeEntryKey(d, he);
+ dictFreeEntryVal(d, he);
+ }
+ _dictFree(he);
+ d->ht[table].used--;
+ return DICT_OK;
}
- _dictFree(he);
- ht->used--;
- return DICT_OK;
+ prevHe = he;
+ he = he->next;
}
- prevHe = he;
- he = he->next;
+ if (!dictIsRehashing(d)) break;
}
return DICT_ERR; /* not found */
}
return dictGenericDelete(ht,key,1);
}
-/* Destroy an entire hash table */
-int _dictClear(dict *ht)
+/* Destroy an entire dictionary */
+int _dictClear(dict *d, dictht *ht)
{
unsigned long i;
if ((he = ht->table[i]) == NULL) continue;
while(he) {
nextHe = he->next;
- dictFreeEntryKey(ht, he);
- dictFreeEntryVal(ht, he);
+ dictFreeEntryKey(d, he);
+ dictFreeEntryVal(d, he);
_dictFree(he);
ht->used--;
he = nextHe;
}
/* Clear & Release the hash table */
-void dictRelease(dict *ht)
+void dictRelease(dict *d)
{
- _dictClear(ht);
- _dictFree(ht);
+ _dictClear(d,&d->ht[0]);
+ _dictClear(d,&d->ht[1]);
+ _dictFree(d);
}
-dictEntry *dictFind(dict *ht, const void *key)
+dictEntry *dictFind(dict *d, const void *key)
{
dictEntry *he;
- unsigned int h;
-
- if (ht->size == 0) return NULL;
- h = dictHashKey(ht, key) & ht->sizemask;
- he = ht->table[h];
- while(he) {
- if (dictCompareHashKeys(ht, key, he->key))
- return he;
- he = he->next;
+ unsigned int h, idx, table;
+
+ if (d->ht[0].size == 0) return NULL; /* We don't have a table at all */
+ if (dictIsRehashing(d)) _dictRehashStep(d);
+ h = dictHashKey(d, key);
+ for (table = 0; table <= 1; table++) {
+ idx = h & d->ht[table].sizemask;
+ he = d->ht[table].table[idx];
+ while(he) {
+ if (dictCompareHashKeys(d, key, he->key))
+ return he;
+ he = he->next;
+ }
+ if (!dictIsRehashing(d)) return NULL;
}
return NULL;
}
-dictIterator *dictGetIterator(dict *ht)
+void *dictFetchValue(dict *d, const void *key) {
+ dictEntry *he;
+
+ he = dictFind(d,key);
+ return he ? dictGetEntryVal(he) : NULL;
+}
+
+dictIterator *dictGetIterator(dict *d)
{
dictIterator *iter = _dictAlloc(sizeof(*iter));
- iter->ht = ht;
+ iter->d = d;
+ iter->table = 0;
iter->index = -1;
iter->entry = NULL;
iter->nextEntry = NULL;
{
while (1) {
if (iter->entry == NULL) {
+ dictht *ht = &iter->d->ht[iter->table];
+ if (iter->index == -1 && iter->table == 0) iter->d->iterators++;
iter->index++;
- if (iter->index >=
- (signed)iter->ht->size) break;
- iter->entry = iter->ht->table[iter->index];
+ if (iter->index >= (signed) ht->size) {
+ if (dictIsRehashing(iter->d) && iter->table == 0) {
+ iter->table++;
+ iter->index = 0;
+ ht = &iter->d->ht[1];
+ } else {
+ break;
+ }
+ }
+ iter->entry = ht->table[iter->index];
} else {
iter->entry = iter->nextEntry;
}
void dictReleaseIterator(dictIterator *iter)
{
+ if (!(iter->index == -1 && iter->table == 0)) iter->d->iterators--;
_dictFree(iter);
}
/* Return a random entry from the hash table. Useful to
* implement randomized algorithms */
-dictEntry *dictGetRandomKey(dict *ht)
+dictEntry *dictGetRandomKey(dict *d)
{
- dictEntry *he;
+ dictEntry *he, *orighe;
unsigned int h;
int listlen, listele;
- if (ht->used == 0) return NULL;
- do {
- h = random() & ht->sizemask;
- he = ht->table[h];
- } while(he == NULL);
+ if (dictSize(d) == 0) return NULL;
+ if (dictIsRehashing(d)) _dictRehashStep(d);
+ if (dictIsRehashing(d)) {
+ do {
+ h = random() % (d->ht[0].size+d->ht[1].size);
+ he = (h >= d->ht[0].size) ? d->ht[1].table[h - d->ht[0].size] :
+ d->ht[0].table[h];
+ } while(he == NULL);
+ } else {
+ do {
+ h = random() & d->ht[0].sizemask;
+ he = d->ht[0].table[h];
+ } while(he == NULL);
+ }
/* Now we found a non empty bucket, but it is a linked
* list and we need to get a random element from the list.
- * The only sane way to do so is to count the element and
+ * The only sane way to do so is counting the elements and
* select a random index. */
listlen = 0;
+ orighe = he;
while(he) {
he = he->next;
listlen++;
}
listele = random() % listlen;
- he = ht->table[h];
+ he = orighe;
while(listele--) he = he->next;
return he;
}
/* ------------------------- private functions ------------------------------ */
/* Expand the hash table if needed */
-static int _dictExpandIfNeeded(dict *ht)
+static int _dictExpandIfNeeded(dict *d)
{
/* If the hash table is empty expand it to the intial size,
* if the table is "full" dobule its size. */
- if (ht->size == 0)
- return dictExpand(ht, DICT_HT_INITIAL_SIZE);
- if (ht->used == ht->size)
- return dictExpand(ht, ht->size*2);
+ if (dictIsRehashing(d)) return DICT_OK;
+ if (d->ht[0].size == 0)
+ return dictExpand(d, DICT_HT_INITIAL_SIZE);
+ if (d->ht[0].used >= d->ht[0].size && dict_can_resize)
+ return dictExpand(d, ((d->ht[0].size > d->ht[0].used) ?
+ d->ht[0].size : d->ht[0].used)*2);
return DICT_OK;
}
/* Returns the index of a free slot that can be populated with
* an hash entry for the given 'key'.
- * If the key already exists, -1 is returned. */
-static int _dictKeyIndex(dict *ht, const void *key)
+ * If the key already exists, -1 is returned.
+ *
+ * Note that if we are in the process of rehashing the hash table, the
+ * index is always returned in the context of the second (new) hash table. */
+static int _dictKeyIndex(dict *d, const void *key)
{
- unsigned int h;
+ unsigned int h, idx, table;
dictEntry *he;
/* Expand the hashtable if needed */
- if (_dictExpandIfNeeded(ht) == DICT_ERR)
+ if (_dictExpandIfNeeded(d) == DICT_ERR)
return -1;
/* Compute the key hash value */
- h = dictHashKey(ht, key) & ht->sizemask;
- /* Search if this slot does not already contain the given key */
- he = ht->table[h];
- while(he) {
- if (dictCompareHashKeys(ht, key, he->key))
- return -1;
- he = he->next;
+ h = dictHashKey(d, key);
+ for (table = 0; table <= 1; table++) {
+ idx = h & d->ht[table].sizemask;
+ /* Search if this slot does not already contain the given key */
+ he = d->ht[table].table[idx];
+ while(he) {
+ if (dictCompareHashKeys(d, key, he->key))
+ return -1;
+ he = he->next;
+ }
+ if (!dictIsRehashing(d)) break;
}
- return h;
+ return idx;
}
-void dictEmpty(dict *ht) {
- _dictClear(ht);
+void dictEmpty(dict *d) {
+ _dictClear(d,&d->ht[0]);
+ _dictClear(d,&d->ht[1]);
+ d->rehashidx = -1;
+ d->iterators = 0;
}
#define DICT_STATS_VECTLEN 50
-void dictPrintStats(dict *ht) {
+static void _dictPrintStatsHt(dictht *ht) {
unsigned long i, slots = 0, chainlen, maxchainlen = 0;
unsigned long totchainlen = 0;
unsigned long clvector[DICT_STATS_VECTLEN];
}
}
+void dictPrintStats(dict *d) {
+ _dictPrintStatsHt(&d->ht[0]);
+ if (dictIsRehashing(d)) {
+ printf("-- Rehashing into ht[1]:\n");
+ _dictPrintStatsHt(&d->ht[1]);
+ }
+}
+
+void dictEnableResize(void) {
+ dict_can_resize = 1;
+}
+
+void dictDisableResize(void) {
+ dict_can_resize = 0;
+}
+
/* ----------------------- StringCopy Hash Table Type ------------------------*/
static unsigned int _dictStringCopyHTHashFunction(const void *key)
projects / redis.git / blobdiff