X-Git-Url: https://git.saurik.com/redis.git/blobdiff_plain/794e6ce14ff85f00b0d3e86365e9cc45a90d3bcf..681c1910064356b330e92f31374058788059e53c:/src/t_set.c diff --git a/src/t_set.c b/src/t_set.c index 3cf1cf00..46a0c6ee 100644 --- a/src/t_set.c +++ b/src/t_set.c @@ -1,9 +1,40 @@ +/* + * Copyright (c) 2009-2012, Salvatore Sanfilippo + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * * Redistributions of source code must retain the above copyright notice, + * this list of conditions and the following disclaimer. + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * * Neither the name of Redis nor the names of its contributors may be used + * to endorse or promote products derived from this software without + * specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + #include "redis.h" /*----------------------------------------------------------------------------- * Set Commands *----------------------------------------------------------------------------*/ +void sunionDiffGenericCommand(redisClient *c, robj **setkeys, int setnum, robj *dstkey, int op); + /* Factory method to return a set that *can* hold "value". When the object has * an integer-encodable value, an intset will be returned. Otherwise a regular * hash table. */ @@ -185,7 +216,7 @@ unsigned long setTypeSize(robj *subject) { } /* Convert the set to specified encoding. The resulting dict (when converting - * to a hashtable) is presized to hold the number of elements in the original + * to a hash table) is presized to hold the number of elements in the original * set. */ void setTypeConvert(robj *setobj, int enc) { setTypeIterator *si; @@ -360,11 +391,165 @@ void spopCommand(redisClient *c) { server.dirty++; } +/* handle the "SRANDMEMBER key " variant. The normal version of the + * command is handled by the srandmemberCommand() function itself. */ + +/* How many times bigger should be the set compared to the requested size + * for us to don't use the "remove elements" strategy? Read later in the + * implementation for more info. */ +#define SRANDMEMBER_SUB_STRATEGY_MUL 3 + +void srandmemberWithCountCommand(redisClient *c) { + long l; + unsigned long count, size; + int uniq = 1; + robj *set, *ele; + int64_t llele; + int encoding; + + dict *d; + + if (getLongFromObjectOrReply(c,c->argv[2],&l,NULL) != REDIS_OK) return; + if (l >= 0) { + count = (unsigned) l; + } else { + /* A negative count means: return the same elements multiple times + * (i.e. don't remove the extracted element after every extraction). */ + count = -l; + uniq = 0; + } + + if ((set = lookupKeyReadOrReply(c,c->argv[1],shared.emptymultibulk)) + == NULL || checkType(c,set,REDIS_SET)) return; + size = setTypeSize(set); + + /* If count is zero, serve it ASAP to avoid special cases later. */ + if (count == 0) { + addReply(c,shared.emptymultibulk); + return; + } + + /* CASE 1: The count was negative, so the extraction method is just: + * "return N random elements" sampling the whole set every time. + * This case is trivial and can be served without auxiliary data + * structures. */ + if (!uniq) { + addReplyMultiBulkLen(c,count); + while(count--) { + encoding = setTypeRandomElement(set,&ele,&llele); + if (encoding == REDIS_ENCODING_INTSET) { + addReplyBulkLongLong(c,llele); + } else { + addReplyBulk(c,ele); + } + } + return; + } + + /* CASE 2: + * The number of requested elements is greater than the number of + * elements inside the set: simply return the whole set. */ + if (count >= size) { + sunionDiffGenericCommand(c,c->argv,c->argc-1,NULL,REDIS_OP_UNION); + return; + } + + /* For CASE 3 and CASE 4 we need an auxiliary dictionary. */ + d = dictCreate(&setDictType,NULL); + + /* CASE 3: + * The number of elements inside the set is not greater than + * SRANDMEMBER_SUB_STRATEGY_MUL times the number of requested elements. + * In this case we create a set from scratch with all the elements, and + * subtract random elements to reach the requested number of elements. + * + * This is done because if the number of requsted elements is just + * a bit less than the number of elements in the set, the natural approach + * used into CASE 3 is highly inefficient. */ + if (count*SRANDMEMBER_SUB_STRATEGY_MUL > size) { + setTypeIterator *si; + + /* Add all the elements into the temporary dictionary. */ + si = setTypeInitIterator(set); + while((encoding = setTypeNext(si,&ele,&llele)) != -1) { + int retval; + + if (encoding == REDIS_ENCODING_INTSET) { + retval = dictAdd(d,createStringObjectFromLongLong(llele),NULL); + } else if (ele->encoding == REDIS_ENCODING_RAW) { + retval = dictAdd(d,dupStringObject(ele),NULL); + } else if (ele->encoding == REDIS_ENCODING_INT) { + retval = dictAdd(d, + createStringObjectFromLongLong((long)ele->ptr),NULL); + } + redisAssert(retval == DICT_OK); + } + setTypeReleaseIterator(si); + redisAssert(dictSize(d) == size); + + /* Remove random elements to reach the right count. */ + while(size > count) { + dictEntry *de; + + de = dictGetRandomKey(d); + dictDelete(d,dictGetKey(de)); + size--; + } + } + + /* CASE 4: We have a big set compared to the requested number of elements. + * In this case we can simply get random elements from the set and add + * to the temporary set, trying to eventually get enough unique elements + * to reach the specified count. */ + else { + unsigned long added = 0; + + while(added < count) { + encoding = setTypeRandomElement(set,&ele,&llele); + if (encoding == REDIS_ENCODING_INTSET) { + ele = createStringObjectFromLongLong(llele); + } else if (ele->encoding == REDIS_ENCODING_RAW) { + ele = dupStringObject(ele); + } else if (ele->encoding == REDIS_ENCODING_INT) { + ele = createStringObjectFromLongLong((long)ele->ptr); + } + /* Try to add the object to the dictionary. If it already exists + * free it, otherwise increment the number of objects we have + * in the result dictionary. */ + if (dictAdd(d,ele,NULL) == DICT_OK) + added++; + else + decrRefCount(ele); + } + } + + /* CASE 3 & 4: send the result to the user. */ + { + dictIterator *di; + dictEntry *de; + + addReplyMultiBulkLen(c,count); + di = dictGetIterator(d); + while((de = dictNext(di)) != NULL) + addReplyBulk(c,dictGetKey(de)); + dictReleaseIterator(di); + dictRelease(d); + } +} + void srandmemberCommand(redisClient *c) { robj *set, *ele; int64_t llele; int encoding; + if (c->argc == 3) { + srandmemberWithCountCommand(c); + return; + } else if (c->argc > 3) { + addReply(c,shared.syntaxerr); + return; + } + if ((set = lookupKeyReadOrReply(c,c->argv[1],shared.nullbulk)) == NULL || checkType(c,set,REDIS_SET)) return;