From f4b0c6b7ff2323dac73392aa71d1bac7bae6e1a8 Mon Sep 17 00:00:00 2001
From: fatkodima <fatkodima123@gmail.com>
Date: Sun, 3 Jul 2022 19:28:14 +0300
Subject: [PATCH] Add ability to clear namespaces

---
 CHANGELOG.md           |  3 +++
 lib/redis/namespace.rb | 31 +++++++++++++++++++++++++++++++
 spec/redis_spec.rb     | 26 ++++++++++++++++++++++++++
 3 files changed, 60 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4f5203a..148d5f4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,9 @@
 
 ## x.y.z
 
+- Add ability to clear namespaces (#202). This operation can run for a very long time if the namespace contains
+  lots of keys! It should be used in tests, or when the namespace is small enough and you are sure you know what you are doing.
+
 ## 1.9.0
 
 - Accept Proc as a namespace (#203)
diff --git a/lib/redis/namespace.rb b/lib/redis/namespace.rb
index 85172a7..cc29f26 100644
--- a/lib/redis/namespace.rb
+++ b/lib/redis/namespace.rb
@@ -330,6 +330,32 @@ def eval(*args)
     end
     ruby2_keywords(:eval) if respond_to?(:ruby2_keywords, true)
 
+    # This operation can run for a very long time if the namespace contains lots of keys!
+    # It should be used in tests, or when the namespace is small enough
+    # and you are sure you know what you are doing.
+    def clear
+      if warning?
+        warn("This operation can run for a very long time if the namespace contains lots of keys! " +
+             "It should be used in tests, or when the namespace is small enough " +
+             "and you are sure you know what you are doing.")
+      end
+
+      batch_size = 1000
+
+      if supports_scan?
+        cursor = "0"
+        begin
+          cursor, keys = scan(cursor, count: batch_size)
+          del(*keys) unless keys.empty?
+        end until cursor == "0"
+      else
+        all_keys = keys("*")
+        all_keys.each_slice(batch_size) do |keys|
+          del(*keys)
+        end
+      end
+    end
+
     ADMINISTRATIVE_COMMANDS.keys.each do |command|
       define_method(command) do |*args, &block|
         raise NoMethodError if deprecations?
@@ -591,5 +617,10 @@ def create_enumerator(&block)
         Enumerator.new(&block)
       end
     end
+
+    def supports_scan?
+      redis_version = @redis.info["redis_version"]
+      Gem::Version.new(redis_version) >= Gem::Version.new("2.8.0")
+    end
   end
 end
diff --git a/spec/redis_spec.rb b/spec/redis_spec.rb
index 49993d1..1e5848d 100644
--- a/spec/redis_spec.rb
+++ b/spec/redis_spec.rb
@@ -1048,4 +1048,30 @@
       expect(sub_sub_namespaced.full_namespace).to eql("ns:sub1:sub2")
     end
   end
+
+  describe :clear do
+    it "warns with helpful output" do
+      expect { @namespaced.clear }.to output(/can run for a very long time/).to_stderr
+    end
+
+    it "should delete all the keys" do
+      @redis.set("foo", "bar")
+      @namespaced.mset("foo1", "bar", "foo2", "bar")
+      capture_stderr { @namespaced.clear }
+
+      expect(@redis.keys).to eq ["foo"]
+      expect(@namespaced.keys).to be_empty
+    end
+
+    it "should delete all the keys in older redis" do
+      allow(@redis).to receive(:info).and_return({ "redis_version" => "2.7.0" })
+
+      @redis.set("foo", "bar")
+      @namespaced.mset("foo1", "bar", "foo2", "bar")
+      capture_stderr { @namespaced.clear }
+
+      expect(@redis.keys).to eq ["foo"]
+      expect(@namespaced.keys).to be_empty
+    end
+  end
 end