From e6b0e8d9ec4561a07864358af8d2d4e81ac413fc Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Thu, 19 Apr 2018 16:25:29 +0200
Subject: [PATCH] Streams: XTRIM command added.

---
 src/server.c   |  1 +
 src/server.h   |  1 +
 src/t_stream.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+)

diff --git a/src/server.c b/src/server.c
index 2cc6b6f5..404429be 100644
--- a/src/server.c
+++ b/src/server.c
@@ -314,6 +314,7 @@ struct redisCommand redisCommandTable[] = {
     {"xclaim",xclaimCommand,-5,"wF",0,NULL,1,1,1,0,0},
     {"xinfo",xinfoCommand,-2,"r",0,NULL,2,2,1,0,0},
     {"xdel",xdelCommand,-2,"wF",0,NULL,1,1,1,0,0},
+    {"xtrim",xtrimCommand,-2,"wF",0,NULL,1,1,1,0,0},
     {"post",securityWarningCommand,-1,"lt",0,NULL,0,0,0,0,0},
     {"host:",securityWarningCommand,-1,"lt",0,NULL,0,0,0,0,0},
     {"latency",latencyCommand,-2,"aslt",0,NULL,0,0,0,0,0}
diff --git a/src/server.h b/src/server.h
index 66581eaa..172e99c8 100644
--- a/src/server.h
+++ b/src/server.h
@@ -2054,6 +2054,7 @@ void xpendingCommand(client *c);
 void xclaimCommand(client *c);
 void xinfoCommand(client *c);
 void xdelCommand(client *c);
+void xtrimCommand(client *c);
 
 #if defined(__GNUC__)
 void *calloc(size_t count, size_t size) __attribute__ ((deprecated));
diff --git a/src/t_stream.c b/src/t_stream.c
index ad47941a..1e46c636 100644
--- a/src/t_stream.c
+++ b/src/t_stream.c
@@ -2024,6 +2024,74 @@ void xdelCommand(client *c) {
     server.dirty += deleted;
     addReplyLongLong(c,deleted);
 }
+
+/* General form: XTRIM <key> [... options ...]
+ *
+ * List of options:
+ *
+ * MAXLEN [~] <count>       -- Trim so that the stream will be capped at
+ *                             the specified length. Use ~ before the
+ *                             count in order to demand approximated trimming
+ *                             (like XADD MAXLEN option).
+ */
+
+#define TRIM_STRATEGY_NONE 0
+#define TRIM_STRATEGY_MAXLEN 1
+void xtrimCommand(client *c) {
+    robj *o;
+
+    /* If the key does not exist, we are ok returning zero, that is, the
+     * number of elements removed from the stream. */
+    if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.czero)) == NULL
+        || checkType(c,o,OBJ_STREAM)) return;
+    stream *s = o->ptr;
+
+    /* Argument parsing. */
+    int trim_strategy = TRIM_STRATEGY_NONE;
+    long long maxlen = 0;   /* 0 means no maximum length. */
+    int approx_maxlen = 0;  /* If 1 only delete whole radix tree nodes, so
+                               the maxium length is not applied verbatim. */
+
+    /* Parse options. */
+    int i = 2; /* Start of options. */
+    for (; i < c->argc; i++) {
+        int moreargs = (c->argc-1) - i; /* Number of additional arguments. */
+        char *opt = c->argv[i]->ptr;
+        if (!strcasecmp(opt,"maxlen") && moreargs) {
+            trim_strategy = TRIM_STRATEGY_MAXLEN;
+            char *next = c->argv[i+1]->ptr;
+            /* Check for the form MAXLEN ~ <count>. */
+            if (moreargs >= 2 && next[0] == '~' && next[1] == '\0') {
+                approx_maxlen = 1;
+                i++;
+            }
+            if (getLongLongFromObjectOrReply(c,c->argv[i+1],&maxlen,NULL)
+                != C_OK) return;
+            i++;
+        } else {
+            addReply(c,shared.syntaxerr);
+            return;
+        }
+    }
+
+    /* Perform the trimming. */
+    int64_t deleted = 0;
+    if (trim_strategy == TRIM_STRATEGY_MAXLEN) {
+        deleted = streamTrimByLength(s,maxlen,approx_maxlen);
+    } else {
+        addReplyError(c,"XTRIM called without an option to trim the stream");
+        return;
+    }
+
+    /* Propagate the write if needed. */
+    if (deleted) {
+        signalModifiedKey(c->db,c->argv[1]);
+        notifyKeyspaceEvent(NOTIFY_STREAM,"xtrim",c->argv[1],c->db->id);
+        server.dirty += deleted;
+    }
+    addReplyLongLong(c,deleted);
+}
+
 /* XINFO CONSUMERS key group
  * XINFO GROUPS <key>
  * XINFO STREAM <key>