From d4f81ebdba7eadcb89b91377fb9091ef7e0513b7 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Fri, 2 Mar 2018 17:24:00 +0100
Subject: CG: XGROUP DELCONSUMER implemented.

---
 src/t_stream.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/src/t_stream.c b/src/t_stream.c
index ed3544374..a2404244c 100644
--- a/src/t_stream.c
+++ b/src/t_stream.c
@@ -1351,6 +1351,33 @@ streamConsumer *streamLookupConsumer(streamCG *cg, sds name, int create) {
     return consumer;
 }
 
+/* Delete the consumer specified in the consumer group 'cg'. The consumer
+ * may have pending messages: they are removed from the PEL, and the number
+ * of pending messages "lost" is returned. */
+uint64_t streamDelConsumer(streamCG *cg, sds name) {
+    streamConsumer *consumer = streamLookupConsumer(cg,name,0);
+    if (consumer == NULL) return 0;
+
+    uint64_t retval = raxSize(consumer->pel);
+
+    /* Iterate all the consumer pending messages, deleting every corresponding
+     * entry from the global entry. */
+    raxIterator ri;
+    raxStart(&ri,consumer->pel);
+    raxSeek(&ri,"^",NULL,0);
+    while(raxNext(&ri)) {
+        streamNACK *nack = ri.data;
+        raxRemove(cg->pel,ri.key,ri.key_len,NULL);
+        streamFreeNACK(nack);
+    }
+    raxStop(&ri);
+
+    /* Deallocate the consumer. */
+    raxRemove(cg->consumers,(unsigned char*)name,sdslen(name),NULL);
+    streamFreeConsumer(consumer);
+    return retval;
+}
+
 /* -----------------------------------------------------------------------
  * Consumer groups commands
  * ----------------------------------------------------------------------- */
@@ -1370,6 +1397,8 @@ NULL
     };
     stream *s = NULL;
     sds grpname = NULL;
+    streamCG *cg = NULL;
+    char *opt = c->argv[1]->ptr; /* Subcommand name. */
 
     /* Lookup the key now, this is common for all the subcommands but HELP. */
     if (c->argc >= 4) {
@@ -1377,9 +1406,21 @@ NULL
         if (o == NULL) return;
         s = o->ptr;
         grpname = c->argv[3]->ptr;
+
+        /* Certain subcommands require the group to exist. */
+        if ((cg = streamLookupCG(s,grpname)) == NULL &&
+            (!strcasecmp(opt,"SETID") ||
+             !strcasecmp(opt,"DELGROUP") ||
+             !strcasecmp(opt,"DELCONSUMER")))
+        {
+            addReplyErrorFormat(c, "-NOGROUP No such consumer group '%s' "
+                                   "for key name '%s'",
+                                   grpname, c->argv[2]->ptr);
+            return;
+        }
     }
 
-    char *opt = c->argv[1]->ptr;
+    /* Dispatch the different subcommands. */
     if (!strcasecmp(opt,"CREATE") && c->argc == 5) {
         streamID id;
         if (!strcmp(c->argv[4]->ptr,"$")) {
@@ -1397,6 +1438,10 @@ NULL
     } else if (!strcasecmp(opt,"SETID") && c->argc == 5) {
     } else if (!strcasecmp(opt,"DELGROUP") && c->argc == 4) {
     } else if (!strcasecmp(opt,"DELCONSUMER") && c->argc == 5) {
+        /* Delete the consumer and returns the number of pending messages
+         * that were yet associated with such a consumer. */
+        long long pending = streamDelConsumer(cg,c->argv[4]->ptr);
+        addReplyLongLong(c,pending);
     } else if (!strcasecmp(opt,"HELP")) {
         addReplyHelp(c, help);
     } else {
-- 
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