1.BRPOP、BLPOP
BLPOP：
BLPOP 是阻塞式列表的彈出原語。 它是命令 LPOP 的阻塞版本，這是因為當給定列表內沒有任何元素可供彈出的時候，
連線將被 BLPOP 命令阻塞。 當給定多個 key 引數時，按引數 key 的先後順序依次檢查各個列表，彈出第一個非空列表的頭元素。
BRPOP:
BRPOP 是一個阻塞的列表彈出原語。 它是 RPOP 的阻塞版本，因為這個命令會在給定list無法彈出任何元素的時候阻塞連線。 該命令會按照給出的 key 順序檢視 list，並在找到的第一個非空 list 的尾部彈出一個元素。
請在 BLPOP 文件 中檢視該命令的準確語義，因為 BRPOP 和 BLPOP 基本是完全一樣的，除了它們一個是從尾部彈出元素，而另一個是從頭部彈出元素。
時間複雜度 :O(1)
127.0.0.1:6379> rpush order 10001 (integer) 1 127.0.0.1:6379> rpush order 10002 (integer) 2 127.0.0.1:6379> rpush order 10003 (integer) 3 127.0.0.1:6379> rpush order 10004 (integer) 4 127.0.0.1:6379> rpush order 10005 (integer) 5 127.0.0.1:6379> rpush order 10006 (integer) 1 127.0.0.1:6379>
127.0.0.1:6379> brpop order 0 1) "order" 2) "10005" 127.0.0.1:6379> brpop order 0 1) "order" 2) "10004" 127.0.0.1:6379> brpop order 0 1) "order" 2) "10003" 127.0.0.1:6379> brpop order 0 1) "order" 2) "10002" 127.0.0.1:6379> brpop order 0 1) "order" 2) "10001" 127.0.0.1:6379> brpop order 0 1) "order" 2) "10006" (2765.54s) 127.0.0.1:6379>
原始碼解析
void blpopCommand(client *c) { blockingPopGenericCommand(c,LIST_HEAD); } void brpopCommand(client *c) { blockingPopGenericCommand(c,LIST_TAIL); }
blockingPopGenericCommand
/* Blocking RPOP/LPOP */ void blockingPopGenericCommand(client *c, int where) { robj *o; mstime_t timeout; int j; if (getTimeoutFromObjectOrReply(c,c->argv[c->argc-1],&timeout,UNIT_SECONDS) != C_OK) return; for (j = 1; j < c->argc-1; j++) { o = lookupKeyWrite(c->db,c->argv[j]); if (o != NULL) { if (o->type != OBJ_LIST) { addReply(c,shared.wrongtypeerr); return; } else { if (listTypeLength(o) != 0) { /* Non empty list, this is like a non normal [LR]POP. */ char *event = (where == LIST_HEAD) ? "lpop" : "rpop"; robj *value = listTypePop(o,where); serverAssert(value != NULL); addReplyArrayLen(c,2); addReplyBulk(c,c->argv[j]); addReplyBulk(c,value); decrRefCount(value); notifyKeyspaceEvent(NOTIFY_LIST,event, c->argv[j],c->db->id); if (listTypeLength(o) == 0) { dbDelete(c->db,c->argv[j]); notifyKeyspaceEvent(NOTIFY_GENERIC,"del", c->argv[j],c->db->id); } signalModifiedKey(c,c->db,c->argv[j]); server.dirty++; /* Replicate it as an [LR]POP instead of B[LR]POP. */ rewriteClientCommandVector(c,2, (where == LIST_HEAD) ? shared.lpop : shared.rpop, c->argv[j]); return; } } } } /* If we are inside a MULTI/EXEC and the list is empty the only thing * we can do is treating it as a timeout (even with timeout 0). */ if (c->flags & CLIENT_MULTI) { addReplyNullArray(c); return; } /* If the list is empty or the key does not exists we must block */ blockForKeys(c,BLOCKED_LIST,c->argv + 1,c->argc - 2,timeout,NULL,NULL); }
blockForKeys
void blockForKeys(client *c, int btype, robj **keys, int numkeys, mstime_t timeout, robj *target, streamID *ids) { dictEntry *de; list *l; int j; c->bpop.timeout = timeout; c->bpop.target = target; if (target != NULL) incrRefCount(target); for (j = 0; j < numkeys; j++) { /* Allocate our bkinfo structure, associated to each key the client * is blocked for. */ bkinfo *bki = zmalloc(sizeof(*bki)); if (btype == BLOCKED_STREAM) bki->stream_id = ids[j]; /* If the key already exists in the dictionary ignore it. */ if (dictAdd(c->bpop.keys,keys[j],bki) != DICT_OK) { zfree(bki); continue; } incrRefCount(keys[j]); /* And in the other "side", to map keys -> clients */ de = dictFind(c->db->blocking_keys,keys[j]); if (de == NULL) { int retval; /* For every key we take a list of clients blocked for it */ l = listCreate(); retval = dictAdd(c->db->blocking_keys,keys[j],l); incrRefCount(keys[j]); serverAssertWithInfo(c,keys[j],retval == DICT_OK); } else { l = dictGetVal(de); } listAddNodeTail(l,c); bki->listnode = listLast(l); } blockClient(c,btype); }
blockClient
void blockClient(client *c, int btype) { c->flags |= CLIENT_BLOCKED; c->btype = btype; server.blocked_clients++; server.blocked_clients_by_type[btype]++; addClientToTimeoutTable(c); }
addClientToTimeoutTable
void addClientToTimeoutTable(client *c) { if (c->bpop.timeout == 0) return; uint64_t timeout = c->bpop.timeout; unsigned char buf[CLIENT_ST_KEYLEN]; encodeTimeoutKey(buf,timeout,c); if (raxTryInsert(server.clients_timeout_table,buf,sizeof(buf),NULL,NULL)) c->flags |= CLIENT_IN_TO_TABLE; }
2.LINDEX
返回列表裡的元素的索引 index 儲存在 key 裡面。 下標是從0開始索引的，所以 0 是表示第一個元素，
1 表示第二個元素，並以此類推。 負數索引用於指定從列表尾部開始索引的元素。在這種方法下，-1 表示最後一個元素，-2 表示倒數第二個元素，並以此往前推。
當 key 位置的值不是一個列表的時候，會返回一個error。
時間複雜度：O(N)
127.0.0.1:6379> lpush mylist "World" "Hello" (integer) 2 127.0.0.1:6379> lindex mylist 0 "Hello" 127.0.0.1:6379> lindex mylist 1 "World" 127.0.0.1:6379>
原始碼解析
void lindexCommand(client *c) { robj *o = lookupKeyReadOrReply(c,c->argv[1],shared.null[c->resp]); if (o == NULL || checkType(c,o,OBJ_LIST)) return; long index; robj *value = NULL; if ((getLongFromObjectOrReply(c, c->argv[2], &index, NULL) != C_OK)) return; if (o->encoding == OBJ_ENCODING_QUICKLIST) { quicklistEntry entry; if (quicklistIndex(o->ptr, index, &entry)) { if (entry.value) { value = createStringObject((char*)entry.value,entry.sz); } else { value = createStringObjectFromLongLong(entry.longval); } addReplyBulk(c,value); decrRefCount(value); } else { addReplyNull(c); } } else { serverPanic("Unknown list encoding"); } }
/* Populate 'entry' with the element at the specified zero-based index * where 0 is the head, 1 is the element next to head * and so on. Negative integers are used in order to count * from the tail, -1 is the last element, -2 the penultimate * and so on. If the index is out of range 0 is returned. * * Returns 1 if element found * Returns 0 if element not found */ int quicklistIndex(const quicklist *quicklist, const long long idx, quicklistEntry *entry) { quicklistNode *n; unsigned long long accum = 0; unsigned long long index; int forward = idx < 0 ? 0 : 1; /* < 0 -> reverse, 0+ -> forward */ initEntry(entry); entry->quicklist = quicklist; if (!forward) { index = (-idx) - 1; n = quicklist->tail; } else { index = idx; n = quicklist->head; } if (index >= quicklist->count) return 0; while (likely(n)) { if ((accum + n->count) > index) { break; } else { D("Skipping over (%p) %u at accum %lld", (void *)n, n->count, accum); accum += n->count; n = forward ? n->next : n->prev; } } if (!n) return 0; D("Found node: %p at accum %llu, idx %llu, sub+ %llu, sub- %llu", (void *)n, accum, index, index - accum, (-index) - 1 + accum); entry->node = n; if (forward) { /* forward = normal head-to-tail offset. */ entry->offset = index - accum; } else { /* reverse = need negative offset for tail-to-head, so undo * the result of the original if (index < 0) above. */ entry->offset = (-index) - 1 + accum; } quicklistDecompressNodeForUse(entry->node); entry->zi = ziplistIndex(entry->node->zl, entry->offset); ziplistGet(entry->zi, &entry->value, &entry->sz, &entry->longval); /* The caller will use our result, so we don't re-compress here. * The caller can recompress or delete the node as needed. */ return 1; }
3.LINSERT
把 value 插入存於 key 的列表中在基準值 pivot 的前面或後面。
當 key 不存在時，這個list會被看作是空list，任何操作都不會發生。
當 key 存在，但儲存的不是一個list的時候，會返回error。
時間複雜度：O(N)
127.0.0.1:6379> linsert mylist before "World" "There" (integer) 3 127.0.0.1:6379> lrange mylist 0 -1 1) "Hello" 2) "There" 3) "World" 127.0.0.1:6379>
4.LRANGE
返回儲存在 key 的列表裡指定範圍內的元素。 start 和 end 偏移量都是基於0的下標，即list的第一個元素下標是0（list的表頭），第二個元素下標是1，以此類推。
偏移量也可以是負數，表示偏移量是從list尾部開始計數。 例如， -1 表示列表的最後一個元素，-2 是倒數第二個，以此類推。
時間複雜度：O(S+N)
127.0.0.1:6379> lrange mylist 0 -1 1) "Hello" 2) "There" 3) "World" 127.0.0.1:6379> lrange mylist 0 1 1) "Hello" 2) "There" 127.0.0.1:6379>
原始碼解析
void lrangeCommand(client *c) { robj *o; long start, end, llen, rangelen; if ((getLongFromObjectOrReply(c, c->argv[2], &start, NULL) != C_OK) || (getLongFromObjectOrReply(c, c->argv[3], &end, NULL) != C_OK)) return; if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.emptyarray)) == NULL || checkType(c,o,OBJ_LIST)) return; llen = listTypeLength(o); /* convert negative indexes */ if (start < 0) start = llen+start; if (end < 0) end = llen+end; if (start < 0) start = 0; /* Invariant: start >= 0, so this test will be true when end < 0. * The range is empty when start > end or start >= length. */ if (start > end || start >= llen) { addReply(c,shared.emptyarray); return; } if (end >= llen) end = llen-1; rangelen = (end-start)+1; /* Return the result in form of a multi-bulk reply */ addReplyArrayLen(c,rangelen); if (o->encoding == OBJ_ENCODING_QUICKLIST) { listTypeIterator *iter = listTypeInitIterator(o, start, LIST_TAIL); while(rangelen--) { listTypeEntry entry; listTypeNext(iter, &entry); quicklistEntry *qe = &entry.entry; if (qe->value) { addReplyBulkCBuffer(c,qe->value,qe->sz); } else { addReplyBulkLongLong(c,qe->longval); } } listTypeReleaseIterator(iter); } else { serverPanic("List encoding is not QUICKLIST!"); } }