Add HAPPEND and HAPPENDX commands

src/help.h

@@ -204,6 +204,16 @@ struct commandHelp {
     "Set the string value of a key and return its old value",
     1,
     "1.0.0" },
+    { "HAPPEND",
+    "key field value",
+    "Append a value to a hash field",
+    5,
+    "2.8.0" },
+    { "HAPPENDX",
+    "key field value",
+    "Append a value to a hash field, only if the key exists",
+    5,
+    "2.8.0" },
     { "HDEL",
     "key field [field ...]",
     "Delete one or more hash fields",

src/redis.c

@@ -193,6 +193,8 @@ struct redisCommand redisCommandTable[] = {
     {"hvals",hvalsCommand,2,"rS",0,NULL,1,1,1,0,0},
     {"hgetall",hgetallCommand,2,"r",0,NULL,1,1,1,0,0},
     {"hexists",hexistsCommand,3,"r",0,NULL,1,1,1,0,0},
+    {"happend",happendCommand,4,"wm",0,NULL,1,1,1,0,0},
+    {"happendx",happendxCommand,4,"wm",0,NULL,1,1,1,0,0},
     {"incrby",incrbyCommand,3,"wm",0,NULL,1,1,1,0,0},
     {"decrby",decrbyCommand,3,"wm",0,NULL,1,1,1,0,0},
     {"incrbyfloat",incrbyfloatCommand,3,"wm",0,NULL,1,1,1,0,0},

src/redis.h

@@ -1397,6 +1397,8 @@ void zinterstoreCommand(redisClient *c);
 void hkeysCommand(redisClient *c);
 void hvalsCommand(redisClient *c);
 void hgetallCommand(redisClient *c);
+void happendCommand(redisClient *c);
+void happendxCommand(redisClient *c);
 void hexistsCommand(redisClient *c);
 void configCommand(redisClient *c);
 void hincrbyCommand(redisClient *c);

src/t_hash.c

@@ -163,6 +163,86 @@ int hashTypeExists(robj *o, robj *field) {
     return 0;
 }
 
+/* Append to an element.
+ * Return total length of appended string.
+ * This function will take care of incrementing the reference count of the
+ * retained fields and value objects. */
+size_t hashTypeAppend(robj *o, robj *field, robj *append) {
+    int update = 0;
+    long long totlen = 0;
+    robj *value;
+
+    if (o->encoding == REDIS_ENCODING_ZIPLIST) {
+        unsigned char *zl, *fptr, *vptr;
+        unsigned char *vstr = NULL;
+        unsigned int vlen = UINT_MAX;
+        long long vll = LLONG_MAX;
+        int ret;
+
+        field = getDecodedObject(field);
+        append = getDecodedObject(append);
+
+        zl = o->ptr;
+        fptr = ziplistIndex(zl, ZIPLIST_HEAD);
+        if (fptr != NULL) {
+            fptr = ziplistFind(fptr, field->ptr, sdslen(field->ptr), 1);
+            if (fptr != NULL) {
+                /* Grab pointer to the value (fptr points to the field) */
+                vptr = ziplistNext(zl, fptr);
+                redisAssert(vptr != NULL);
+                update = 1;
+
+                /* Append to current string */
+                ret = ziplistGet(vptr, &vstr, &vlen, &vll);
+                redisAssert(ret);
+                value = createStringObject((char *)vstr, (size_t)vlen);
+                value->ptr = sdscatlen(value->ptr, append->ptr, sdslen(append->ptr));
+
+                /* Delete value */
+                zl = ziplistDelete(zl, &vptr);
+
+                /* Insert new value */
+                zl = ziplistInsert(zl, vptr, value->ptr, sdslen(value->ptr));
+                totlen = sdslen(value->ptr);
+                decrRefCount(value);
+            }
+        }
+
+        if (!update) {
+            /* Push new field/value pair onto the tail of the ziplist */
+            zl = ziplistPush(zl, field->ptr, sdslen(field->ptr), ZIPLIST_TAIL);
+            zl = ziplistPush(zl, append->ptr, sdslen(append->ptr), ZIPLIST_TAIL);
+            totlen = sdslen(append->ptr);
+        }
+
+        o->ptr = zl;
+        decrRefCount(field);
+        decrRefCount(append);
+
+        /* Check if the ziplist needs to be converted to a hash table */
+        if (hashTypeLength(o) > server.hash_max_ziplist_entries)
+            hashTypeConvert(o, REDIS_ENCODING_HT);
+    } else if (o->encoding == REDIS_ENCODING_HT) {
+        /* Append to current string */
+        if ((value = hashTypeGetObject(o,field)) != NULL) {
+            value->ptr = sdscatlen(value->ptr,append->ptr,sdslen(append->ptr));
+        } else {
+            value = append;
+            incrRefCount(value);
+        }
+
+        if (dictReplace(o->ptr, field, value)) { /* Insert */
+            incrRefCount(field);
+        } else { /* Update */
+            update = 1;
+        }
+        totlen = sdslen(value->ptr);
+    } else {
+        redisPanic("Unknown hash encoding");
+    }
+    return totlen;
+}
+
 /* Add an element, discard the old if the key already exists.
  * Return 0 on insert and 1 on update.
  * This function will take care of incrementing the reference count of the
@@ -752,6 +832,34 @@ void hgetallCommand(redisClient *c) {
     genericHgetallCommand(c,REDIS_HASH_KEY|REDIS_HASH_VALUE);
 }
 
+void genericHappendCommand(redisClient *c, int nx) {
+    size_t totlen;
+    robj *o;
+
+    if ((o = hashTypeLookupWriteOrCreate(c,c->argv[1])) == NULL) return;
+    hashTypeTryConversion(o,c->argv,2,3);
+
+    if (!hashTypeExists(o, c->argv[2]) && !nx) {
+        addReply(c, shared.czero);
+        return;
+    } else {
+        hashTypeTryObjectEncoding(o,&c->argv[2], &c->argv[3]);
+        totlen = hashTypeAppend(o,c->argv[2],c->argv[3]);
+        addReplyLongLong(c, totlen);
+        signalModifiedKey(c->db,c->argv[1]);
+        notifyKeyspaceEvent(REDIS_NOTIFY_HASH,"happend",c->argv[1],c->db->id);
+        server.dirty++;
+    }
+}
+
+void happendxCommand(redisClient *c) {
+    genericHappendCommand(c,0);
+}
+
+void happendCommand(redisClient *c) {
+    genericHappendCommand(c,1);
+}
+
 void hexistsCommand(redisClient *c) {
     robj *o;
     if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.czero)) == NULL ||

tests/unit/type/hash.tcl

@@ -107,6 +107,71 @@ start_server {tags {"hash"}} {
         set _ $result
     } {foo}
 
+    test {HAPPEND target key missing - small hash} {
+        set rv {}
+        lappend rv [r happend smallhash __123123123__ foo]
+        lappend rv [r hget smallhash __123123123__]
+        r hdel smallhash __123123123__
+        set _ $rv
+    } {3 foo}
+
+    test {HAPPEND target key exists - small hash} {
+        set rv {}
+        r hset smallhash __123123123__ foo
+        lappend rv [r happend smallhash __123123123__ bar]
+        lappend rv [r hget smallhash __123123123__]
+        r hdel smallhash __123123123__
+        set _ $rv
+    } {6 foobar}
+
+    test {HAPPEND target key missing - big hash} {
+        set rv {}
+        lappend rv [r happend bighash __123123123__ foo]
+        lappend rv [r hget bighash __123123123__]
+        set _ $rv
+    } {3 foo}
+
+    test {HAPPEND target key exists - big hash} {
+        set rv {}
+        r hset bighash __123123123__ foo
+        lappend rv [r happend bighash __123123123__ bar]
+        lappend rv [r hget bighash __123123123__]
+        r hdel bighash __123123123__
+        set _ $rv
+    } {6 foobar}
+
+    test {HAPPENDX target key missing - small hash} {
+        set rv {}
+        lappend rv [r happendx smallhash __123123123__ foo]
+        lappend rv [r hget smallhash __123123123__]
+        set _ $rv
+    } {0 {}}
+
+    test {HAPPENDX target key exists - small hash} {
+        set rv {}
+        r hset smallhash __123123123__ foo
+        lappend rv [r happendx smallhash __123123123__ bar]
+        lappend rv [r hget smallhash __123123123__]
+        r hdel smallhash __123123123__
+        set _ $rv
+    } {6 foobar}
+
+    test {HAPPENDX target key missing - big hash} {
+        set rv {}
+        lappend rv [r happendx bighash __123123123__ foo]
+        lappend rv [r hget bighash __123123123__]
+        set _ $rv
+    } {0 {}}
+
+    test {HAPPENDX target key exists - big hash} {
+        set rv {}
+        r hset bighash __123123123__ foo
+        lappend rv [r happendx bighash __123123123__ bar]
+        lappend rv [r hget bighash __123123123__]
+        r hdel bighash __123123123__
+        set _ $rv
+    } {6 foobar}
+
     test {HMSET wrong number of args} {
         catch {r hmset smallhash key1 val1 key2} err
         format $err