在redis源码从main开始6中看完了客户端发来一个命令在redis中的执行流程,本章我们看一个经常会引起性能问题的命令keys,keys命令用来查找匹配模式的键,下面我们来看看,为什么在数据量巨大的redis中使用keys命令会使得redis无法处理其他请求。具体原因在于,while((de = dictNext(di)) != NULL) 会遍历查找的所有键,判断是否可以匹配
void keysCommand(redisClient *c) {
dictIterator *di;
dictEntry *de;
// 需要匹配的规则
sds pattern = c->argv[1]->ptr;
int plen = sdslen(pattern), allkeys;
unsigned long numkeys = 0;
void *replylen = addDeferredMultiBulkLength(c);
// 安全模式的迭代器
di = dictGetSafeIterator(c->db->dict);
// 是全部key都匹配 keys * 命令
allkeys = (pattern[0] == '*' && pattern[1] == '\0');
while((de = dictNext(di)) != NULL) {
sds key = dictGetKey(de);
robj *keyobj;
// 是所有key都符合, 或者处理匹配
if (allkeys || stringmatchlen(pattern,plen,key,sdslen(key),0)) {
// 创建匹配到的键名字符串对象
keyobj = createStringObject(key,sdslen(key));
// 判断键是否过期了==0是键还存在,会添加到回复中
if (expireIfNeeded(c->db,keyobj) == 0) {
addReplyBulk(c,keyobj);
numkeys++;
}
decrRefCount(keyobj);
}
}
dictReleaseIterator(di);
setDeferredMultiBulkLength(c,replylen,numkeys);
}
/* Glob-style pattern matching. */
int stringmatchlen(const char *pattern, int patternLen,
const char *string, int stringLen, int nocase)
{
while(patternLen) {
switch(pattern[0]) {
case '*':
while (pattern[1] == '*') {
pattern++;
patternLen--;
}
if (patternLen == 1)
return 1; /* match */
while(stringLen) {
if (stringmatchlen(pattern+1, patternLen-1,
string, stringLen, nocase))
return 1; /* match */
string++;
stringLen--;
}
return 0; /* no match */
break;
case '?':
if (stringLen == 0)
return 0; /* no match */
string++;
stringLen--;
break;
case '[':
{
int not, match;
pattern++;
patternLen--;
not = pattern[0] == '^';
if (not) {
pattern++;
patternLen--;
}
match = 0;
while(1) {
if (pattern[0] == '\\') {
pattern++;
patternLen--;
if (pattern[0] == string[0])
match = 1;
} else if (pattern[0] == ']') {
break;
} else if (patternLen == 0) {
pattern--;
patternLen++;
break;
} else if (pattern[1] == '-' && patternLen >= 3) {
int start = pattern[0];
int end = pattern[2];
int c = string[0];
if (start > end) {
int t = start;
start = end;
end = t;
}
if (nocase) {
start = tolower(start);
end = tolower(end);
c = tolower(c);
}
pattern += 2;
patternLen -= 2;
if (c >= start && c <= end)
match = 1;
} else {
if (!nocase) {
if (pattern[0] == string[0])
match = 1;
} else {
if (tolower((int)pattern[0]) == tolower((int)string[0]))
match = 1;
}
}
pattern++;
patternLen--;
}
if (not)
match = !match;
if (!match)
return 0; /* no match */
string++;
stringLen--;
break;
}
case '\\':
if (patternLen >= 2) {
pattern++;
patternLen--;
}
/* fall through */
default:
if (!nocase) {
if (pattern[0] != string[0])
return 0; /* no match */
} else {
if (tolower((int)pattern[0]) != tolower((int)string[0]))
return 0; /* no match */
}
string++;
stringLen--;
break;
}
pattern++;
patternLen--;
if (stringLen == 0) {
while(*pattern == '*') {
pattern++;
patternLen--;
}
break;
}
}
if (patternLen == 0 && stringLen == 0)
return 1;
return 0;
}
基于版本3.0.0版本,点击下载https://download.redis.io/releases/redis-3.0.0.tar.gz
本文地址,https://www.ccagml.com/?p=390