kv: make delete range optional on number of keys

Actually, we may only wanna let the objects with real big number of omap to
use delete range. if not, we find too many tombstones will have side-effects
on performance of kv.

refer: https://github.com/facebook/rocksdb/wiki/DeleteRange-Implementation

Signed-off-by: Zengran Zhang <zhangzengran@sangfor.com.cn>

diff --git a/src/common/options.cc b/src/common/options.cc
index 268f496d8f2e6c8a6d09c0776c108b5d318297a7..d5ecc21c1604b923139b1e87be034bb33db53f83 100644 (file)
--- a/src/common/options.cc
+++ b/src/common/options.cc
@@ -3789,7 +3789,12 @@ std::vector<Option> get_global_options() {
 
     Option("rocksdb_enable_rmrange", Option::TYPE_BOOL, Option::LEVEL_ADVANCED)
     .set_default(false)
-    .set_description(""),
+    .set_description("Refer to github.com/facebook/rocksdb/wiki/DeleteRange-Implementation"),
+
+    Option("rocksdb_max_items_rmrange", Option::TYPE_UINT, Option::LEVEL_ADVANCED)
+    .set_default(1024)
+    .set_description("Delete Range will be called if number of keys exceeded, must enable rocksdb_enable_rmrange first")
+    .add_see_also("rocksdb_enable_rmrange"),
 
     Option("rocksdb_bloom_bits_per_key", Option::TYPE_UINT, Option::LEVEL_ADVANCED)
     .set_default(20)

diff --git a/src/kv/RocksDBStore.cc b/src/kv/RocksDBStore.cc
index f056d8c2abce7421193ed5c0bc401055976e565b..4756697f270c4de0b3996cb65bfde3d067be2ed3 100644 (file)
--- a/src/kv/RocksDBStore.cc
+++ b/src/kv/RocksDBStore.cc
@@ -946,7 +946,25 @@ void RocksDBStore::RocksDBTransactionImpl::rmkeys_by_prefix(const string &prefix
   if (cf) {
     if (db->enable_rmrange) {
       string endprefix("\xff\xff\xff\xff");  // FIXME: this is cheating...
-      bat.DeleteRange(cf, string(), endprefix);
+      if (db->max_items_rmrange) {
+        uint64_t cnt = db->max_items_rmrange;
+        bat.SetSavePoint();
+        auto it = db->get_iterator(prefix);
+        for (it->seek_to_first();
+        it->valid();
+        it->next()) {
+          if (!cnt) {
+            bat.RollbackToSavePoint();
+            bat.DeleteRange(cf, string(), endprefix);
+            return;
+          }
+          bat.Delete(cf, rocksdb::Slice(it->key()));
+          --cnt;
+        }
+        bat.PopSavePoint();
+      } else {
+        bat.DeleteRange(cf, string(), endprefix);
+      }
     } else {
       auto it = db->get_iterator(prefix);
       for (it->seek_to_first();
@@ -959,9 +977,29 @@ void RocksDBStore::RocksDBTransactionImpl::rmkeys_by_prefix(const string &prefix
     if (db->enable_rmrange) {
       string endprefix = prefix;
       endprefix.push_back('\x01');
-      bat.DeleteRange(db->default_cf,
-                     combine_strings(prefix, string()),
-                     combine_strings(endprefix, string()));
+      if (db->max_items_rmrange) {
+        uint64_t cnt = db->max_items_rmrange;
+        bat.SetSavePoint();
+        auto it = db->get_iterator(prefix);
+        for (it->seek_to_first();
+             it->valid();
+             it->next()) {
+          if (!cnt) {
+            bat.RollbackToSavePoint();
+            bat.DeleteRange(db->default_cf,
+                combine_strings(prefix, string()),
+                combine_strings(endprefix, string()));
+            return;
+          }
+          bat.Delete(db->default_cf, combine_strings(prefix, it->key()));
+          --cnt;
+        }
+        bat.PopSavePoint();
+      } else {
+        bat.DeleteRange(db->default_cf,
+            combine_strings(prefix, string()),
+            combine_strings(endprefix, string()));
+      }
     } else {
       auto it = db->get_iterator(prefix);
       for (it->seek_to_first();
@@ -980,7 +1018,28 @@ void RocksDBStore::RocksDBTransactionImpl::rm_range_keys(const string &prefix,
   auto cf = db->get_cf_handle(prefix);
   if (cf) {
     if (db->enable_rmrange) {
-      bat.DeleteRange(cf, rocksdb::Slice(start), rocksdb::Slice(end));
+      if (db->max_items_rmrange) {
+        uint64_t cnt = db->max_items_rmrange;
+        auto it = db->get_iterator(prefix);
+        bat.SetSavePoint();
+        it->lower_bound(start);
+        while (it->valid()) {
+          if (it->key() >= end) {
+            break;
+          }
+          if (!cnt) {
+            bat.RollbackToSavePoint();
+            bat.DeleteRange(cf, rocksdb::Slice(start), rocksdb::Slice(end));
+            return;
+          }
+          bat.Delete(cf, rocksdb::Slice(it->key()));
+          it->next();
+          --cnt;
+        }
+        bat.PopSavePoint();
+      } else {
+        bat.DeleteRange(cf, rocksdb::Slice(start), rocksdb::Slice(end));
+      }
     } else {
       auto it = db->get_iterator(prefix);
       it->lower_bound(start);
@@ -994,10 +1053,35 @@ void RocksDBStore::RocksDBTransactionImpl::rm_range_keys(const string &prefix,
     }
   } else {
     if (db->enable_rmrange) {
-      bat.DeleteRange(
-       db->default_cf,
-       rocksdb::Slice(combine_strings(prefix, start)),
-       rocksdb::Slice(combine_strings(prefix, end)));
+      if (db->max_items_rmrange) {
+        uint64_t cnt = db->max_items_rmrange;
+        auto it = db->get_iterator(prefix);
+        bat.SetSavePoint();
+        it->lower_bound(start);
+        while (it->valid()) {
+          if (it->key() >= end) {
+            break;
+          }
+          if (!cnt) {
+            bat.RollbackToSavePoint();
+            bat.DeleteRange(
+                db->default_cf,
+                rocksdb::Slice(combine_strings(prefix, start)),
+                rocksdb::Slice(combine_strings(prefix, end)));
+            return;
+          }
+          bat.Delete(db->default_cf,
+          combine_strings(prefix, it->key()));
+          it->next();
+          --cnt;
+        }
+        bat.PopSavePoint();
+      } else {
+        bat.DeleteRange(
+            db->default_cf,
+            rocksdb::Slice(combine_strings(prefix, start)),
+            rocksdb::Slice(combine_strings(prefix, end)));
+      }
     } else {
       auto it = db->get_iterator(prefix);
       it->lower_bound(start);

diff --git a/src/kv/RocksDBStore.h b/src/kv/RocksDBStore.h
index 393853d16c0a00c000bf4e04a57c27a23b31d15b..ea7c77d3c767ed01c955ba51f2ab3b4db761a911 100644 (file)
--- a/src/kv/RocksDBStore.h
+++ b/src/kv/RocksDBStore.h
@@ -120,6 +120,7 @@ public:
   bool compact_on_mount;
   bool disableWAL;
   bool enable_rmrange;
+  const uint64_t max_items_rmrange;
   void compact() override;
 
   void compact_async() override {
@@ -159,7 +160,8 @@ public:
     compact_thread(this),
     compact_on_mount(false),
     disableWAL(false),
-    enable_rmrange(cct->_conf->rocksdb_enable_rmrange)
+    enable_rmrange(cct->_conf->rocksdb_enable_rmrange),
+    max_items_rmrange(cct->_conf.get_val<uint64_t>("rocksdb_max_items_rmrange"))
   {}
 
   ~RocksDBStore() override;