添加注释

src/object.c

@@ -465,7 +465,11 @@ robj *tryObjectEncoding(robj *o) {
         /* This object is encodable as a long. Try to use a shared object.
          * Note that we avoid using shared integers when maxmemory is used
          * because every object needs to have a private LRU field for the LRU
-         * algorithm to work well. */
+         * algorithm to work well. 
+         * 
+         * 如果长度小于20，则考虑将value转换long类型
+         * 
+         * */
         if ((server.maxmemory == 0 ||
             !(server.maxmemory_policy & MAXMEMORY_FLAG_NO_SHARED_INTEGERS)) &&
             value >= 0 &&
@@ -490,7 +494,9 @@ robj *tryObjectEncoding(robj *o) {
     /* If the string is small and is still RAW encoded,
      * try the EMBSTR encoding which is more efficient.
      * In this representation the object and the SDS string are allocated
-     * in the same chunk of memory to save space and cache misses. */
+     * in the same chunk of memory to save space and cache misses. 
+     * 对于长度小于44的进行编码
+     * */
     if (len <= OBJ_ENCODING_EMBSTR_SIZE_LIMIT) {
         robj *emb;
 
@@ -508,7 +514,9 @@ robj *tryObjectEncoding(robj *o) {
      *
      * We do that only for relatively large strings as this branch
      * is only entered if the length of the string is greater than
-     * OBJ_ENCODING_EMBSTR_SIZE_LIMIT. */
+     * OBJ_ENCODING_EMBSTR_SIZE_LIMIT. 
+     * 不能编码的字符串释放空闲字节
+     * */
     trimStringObjectIfNeeded(o);
 
     /* Return the original object. */

src/server.h

@@ -645,15 +645,15 @@ typedef struct clientReplyBlock {
  * by integers from 0 (the default database) up to the max configured
  * database. The database number is the 'id' field in the structure. */
 typedef struct redisDb {
-    dict *dict;                 /* The keyspace for this DB */
-    dict *expires;              /* Timeout of keys with a timeout set */
-    dict *blocking_keys;        /* Keys with clients waiting for data (BLPOP)*/
-    dict *ready_keys;           /* Blocked keys that received a PUSH */
-    dict *watched_keys;         /* WATCHED keys for MULTI/EXEC CAS */
-    int id;                     /* Database ID */
-    long long avg_ttl;          /* Average TTL, just for stats */
-    unsigned long expires_cursor; /* Cursor of the active expire cycle. */
-    list *defrag_later;         /* List of key names to attempt to defrag one by one, gradually. */
+    dict *dict;                 /* 键空间字典，存放所有键值对。 */
+    dict *expires;              /*  key的超时时间字典,存放键的过期时间，注意dict和expires中的键都指向同一个键的sds。 */
+    dict *blocking_keys;        /* 阻塞的key:处于阻塞状态的键和对应的client。*/
+    dict *ready_keys;           /* 准备好的key:解除阻塞状态的键和对应的client，与blocking_keys属性相对，为了实现需要阻塞的命令设计 */
+    dict *watched_keys;         /* 执行事务的key:watch的键和对应的client，主要用于事务。 */
+    int id;                     /* 数据库ID */
+    long long avg_ttl;          /* 数据库内所有键的平均生存时间，用于统计 */
+    unsigned long expires_cursor; /* 活动过期周期的光标。 */
+    list *defrag_later;         /*  逐渐尝试逐个碎片整理的key列表 */
 } redisDb;
 
 /* Client MULTI/EXEC state */
@@ -1786,6 +1786,7 @@ int collateStringObjects(robj *a, robj *b);
 int equalStringObjects(robj *a, robj *b);
 unsigned long long estimateObjectIdleTime(robj *o);
 void trimStringObjectIfNeeded(robj *o);
+// 判断只有对string和raw类型进行优化
 #define sdsEncodedObject(objptr) (objptr->encoding == OBJ_ENCODING_RAW || objptr->encoding == OBJ_ENCODING_EMBSTR)
 
 /* Synchronous I/O with timeout */

src/t_string.c

@@ -96,10 +96,12 @@ void setGenericCommand(client *c, int flags, robj *key, robj *val, robj *expire,
 /* SET key value [NX] [XX] [KEEPTTL] [EX <seconds>] [PX <milliseconds>] */
 void setCommand(client *c) {
     int j;
-    robj *expire = NULL;
+    robj *expire = NULL; // 超时时间，robj类型
+     // 字符串的超时时间单位有秒和毫秒两种，程序中根据此值来确认超时的单位，此值只有两个取值，分别为UNIT_SECONDS，UNIT_MILLISECONDS
     int unit = UNIT_SECONDS;
+    // int类型，它是一个二进制串，程序中根据此值来确定key是否应该被设置到数据库。
     int flags = OBJ_SET_NO_FLAGS;
-    // 解析set命令的val值
+    // 解析set命令的NX、XX、EX、PX的值
     for (j = 3; j < c->argc; j++) {
         char *a = c->argv[j]->ptr;
         robj *next = (j == c->argc-1) ? NULL : c->argv[j+1];