RM_ZsetRem: Delete key if empty (#8453)

Without this fix, RM_ZsetRem can leave empty sorted sets which are
not allowed to exist.

Removing from a sorted set while iterating seems to work (while
inserting causes failed assetions). RM_ZsetRangeEndReached is
modified to return 1 if the key doesn't exist, to terminate
iteration when the last element has been removed.

(cherry picked from commit aea6e71ef8)

runtest-moduleapi

@@ -28,4 +28,5 @@ $TCLSH tests/test_helper.tcl \
 --single unit/moduleapi/keyspace_events \
 --single unit/moduleapi/blockedclient \
 --single unit/moduleapi/getkeys \
+--single unit/moduleapi/zset \
 "${@}"

src/module.c

@@ -2508,6 +2508,7 @@ int RM_ZsetRem(RedisModuleKey *key, RedisModuleString *ele, int *deleted) {
     if (key->value && key->value->type != OBJ_ZSET) return REDISMODULE_ERR;
     if (key->value != NULL && zsetDel(key->value,ele->ptr)) {
         if (deleted) *deleted = 1;
+        moduleDelKeyIfEmpty(key);
     } else {
         if (deleted) *deleted = 0;
     }
@@ -2552,6 +2553,7 @@ void RM_ZsetRangeStop(RedisModuleKey *key) {
 
 /* Return the "End of range" flag value to signal the end of the iteration. */
 int RM_ZsetRangeEndReached(RedisModuleKey *key) {
+    if (!key->value || key->value->type != OBJ_ZSET) return 1;
     return key->zer;
 }
 

tests/modules/Makefile

@@ -25,6 +25,7 @@ TEST_MODULES = \
     auth.so \
     keyspace_events.so \
     blockedclient.so \
+    zset.so \
     getkeys.so
 
 

tests/modules/zset.c

@@ -0,0 +1,30 @@
+#include "redismodule.h"
+
+/* ZSET.REM key element
+ *
+ * Removes an occurrence of an element from a sorted set. Replies with the
+ * number of removed elements (0 or 1).
+ */
+int zset_rem(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
+    if (argc != 3) return RedisModule_WrongArity(ctx);
+    RedisModule_AutoMemory(ctx);
+    int keymode = REDISMODULE_READ | REDISMODULE_WRITE;
+    RedisModuleKey *key = RedisModule_OpenKey(ctx, argv[1], keymode);
+    int deleted;
+    if (RedisModule_ZsetRem(key, argv[2], &deleted) == REDISMODULE_OK)
+        return RedisModule_ReplyWithLongLong(ctx, deleted);
+    else
+        return RedisModule_ReplyWithError(ctx, "ERR ZsetRem failed");
+}
+
+int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
+    REDISMODULE_NOT_USED(argv);
+    REDISMODULE_NOT_USED(argc);
+    if (RedisModule_Init(ctx, "zset", 1, REDISMODULE_APIVER_1) ==
+        REDISMODULE_OK &&
+        RedisModule_CreateCommand(ctx, "zset.rem", zset_rem, "",
+                                  1, 1, 1) == REDISMODULE_OK)
+        return REDISMODULE_OK;
+    else
+        return REDISMODULE_ERR;
+}

tests/unit/moduleapi/zset.tcl

@@ -0,0 +1,16 @@
+set testmodule [file normalize tests/modules/zset.so]
+
+start_server {tags {"modules"}} {
+    r module load $testmodule
+
+    test {Module zset rem} {
+        r del k
+        r zadd k 100 hello 200 world
+        assert_equal 1 [r zset.rem k hello]
+        assert_equal 0 [r zset.rem k hello]
+        assert_equal 1 [r exists k]
+        # Check that removing the last element deletes the key
+        assert_equal 1 [r zset.rem k world]
+        assert_equal 0 [r exists k]
+    }
+}