diff --git a/include/collection_manager.h b/include/collection_manager.h
index 02b4dcbe..99de5a8c 100644
--- a/include/collection_manager.h
+++ b/include/collection_manager.h
@@ -201,4 +201,7 @@ public:
     Option<bool> upsert_preset(const std::string & preset_name, const nlohmann::json& preset_config);
 
     Option<bool> delete_preset(const std::string & preset_name);
+
+    static void _get_reference_collection_names(const std::string& filter_query,
+                                                std::set<std::string>& reference_collection_names);
 };
diff --git a/include/string_utils.h b/include/string_utils.h
index 7a3c9fd3..74cfc537 100644
--- a/include/string_utils.h
+++ b/include/string_utils.h
@@ -335,7 +335,4 @@ struct StringUtils {
     static Option<bool> tokenize_filter_query(const std::string& filter_query, std::queue<std::string>& tokens);
 
     static Option<bool> split_include_fields(const std::string& include_fields, std::vector<std::string>& tokens);
-
-    static void get_reference_collection_names(const std::string& filter_query,
-                                               std::set<std::string>& reference_collection_names);
 };
diff --git a/src/collection_manager.cpp b/src/collection_manager.cpp
index 9944b62c..2828a378 100644
--- a/src/collection_manager.cpp
+++ b/src/collection_manager.cpp
@@ -676,13 +676,61 @@ Option<bool> add_unsigned_int_list_param(const std::string& param_name, const st
     return Option<bool>(true);
 }
 
+void CollectionManager::_get_reference_collection_names(const std::string& filter_query,
+                                                        std::set<std::string>& reference_collection_names) {
+    auto size = filter_query.size();
+    for (uint32_t i = 0; i < size;) {
+        auto c = filter_query[i];
+        if (c == ' ' || c == '(' || c == ')') {
+            i++;
+        } else if (c == '&' || c == '|') {
+            i += 2;
+        } else {
+            // Reference filter would start with $ symbol.
+            if (c == '$') {
+                auto open_paren_pos = filter_query.find('(', ++i);
+                if (open_paren_pos == std::string::npos) {
+                    return;
+                }
+
+                auto reference_collection_name = filter_query.substr(i, open_paren_pos - i);
+                StringUtils::trim(reference_collection_name);
+                if (!reference_collection_name.empty()) {
+                    reference_collection_names.insert(reference_collection_name);
+                }
+
+                i = open_paren_pos;
+                int parenthesis_count = 1;
+                while (++i < size && parenthesis_count > 0) {
+                    if (filter_query[i] == '(') {
+                        parenthesis_count++;
+                    } else if (filter_query[i] == ')') {
+                        parenthesis_count--;
+                    }
+                }
+            } else {
+                while (filter_query[++i] != ':');
+                bool in_backtick = false;
+                do {
+                    c = filter_query[++i];
+                    if (c == '`') {
+                        in_backtick = !in_backtick;
+                    }
+                } while (i < size && (in_backtick || (c != '(' && c != ')' &&
+                                                      !(c == '&' && filter_query[i + 1] == '&') &&
+                                                      !(c == '|' && filter_query[i + 1] == '|'))));
+            }
+        }
+    }
+}
+
 void initialize_include_fields_vec(const std::string& filter_query, std::vector<std::string>& include_fields_vec) {
     if (filter_query.empty()) {
         return;
     }
 
     std::set<std::string> reference_collection_names;
-    StringUtils::get_reference_collection_names(filter_query, reference_collection_names);
+    CollectionManager::_get_reference_collection_names(filter_query, reference_collection_names);
     if (reference_collection_names.empty()) {
         return;
     }
diff --git a/src/filter.cpp b/src/filter.cpp
index 5d94c66c..10354ea0 100644
--- a/src/filter.cpp
+++ b/src/filter.cpp
@@ -737,16 +737,16 @@ Option<bool> filter::parse_filter_query(const std::string& filter_query,
         return tokenize_op;
     }
 
-    if (tokens.size() > 100) {
-        return Option<bool>(400, "Filter expression is not valid.");
-    }
-
     std::queue<std::string> postfix;
     Option<bool> toPostfix_op = toPostfix(tokens, postfix);
     if (!toPostfix_op.ok()) {
         return toPostfix_op;
     }
 
+    if (postfix.size() > 100) {
+        return Option<bool>(400, "`filter_by` has too many operations.");
+    }
+
     Option<bool> toParseTree_op = toParseTree(postfix,
                                               root,
                                               search_schema,
diff --git a/src/filter_result_iterator.cpp b/src/filter_result_iterator.cpp
index 08933c70..a85721bb 100644
--- a/src/filter_result_iterator.cpp
+++ b/src/filter_result_iterator.cpp
@@ -1026,6 +1026,9 @@ void filter_result_iterator_t::init() {
             std::vector<std::string> str_tokens;
 
             while (tokenizer.next(str_token, token_index)) {
+                if (str_token.size() > 100) {
+                    str_token.erase(100);
+                }
                 str_tokens.push_back(str_token);
 
                 art_leaf* leaf = (art_leaf *) art_search(t, (const unsigned char*) str_token.c_str(),
diff --git a/src/string_utils.cpp b/src/string_utils.cpp
index d5401ee8..6b320fc2 100644
--- a/src/string_utils.cpp
+++ b/src/string_utils.cpp
@@ -582,54 +582,6 @@ size_t StringUtils::split_facet(const std::string &s, std::vector<std::string> &
     return std::min(end_index, s.size());
 }
 
-void StringUtils::get_reference_collection_names(const std::string& filter_query,
-                                                 std::set<std::string>& reference_collection_names) {
-    auto size = filter_query.size();
-    for (uint32_t i = 0; i < size;) {
-        auto c = filter_query[i];
-        if (c == ' ' || c == '(' || c == ')') {
-            i++;
-        } else if (c == '&' || c == '|') {
-            i += 2;
-        } else {
-            // Reference filter would start with $ symbol.
-            if (c == '$') {
-                auto open_paren_pos = filter_query.find('(', ++i);
-                if (open_paren_pos == std::string::npos) {
-                    return;
-                }
-
-                auto reference_collection_name = filter_query.substr(i, open_paren_pos - i);
-                StringUtils::trim(reference_collection_name);
-                if (!reference_collection_name.empty()) {
-                    reference_collection_names.insert(reference_collection_name);
-                }
-
-                i = open_paren_pos;
-                int parenthesis_count = 1;
-                while (++i < size && parenthesis_count > 0) {
-                    if (filter_query[i] == '(') {
-                        parenthesis_count++;
-                    } else if (filter_query[i] == ')') {
-                        parenthesis_count--;
-                    }
-                }
-            } else {
-                while (filter_query[++i] != ':');
-                bool in_backtick = false;
-                do {
-                    c = filter_query[++i];
-                    if (c == '`') {
-                        in_backtick = !in_backtick;
-                    }
-                } while (i < size && (in_backtick || (c != '(' && c != ')' &&
-                                                      !(c == '&' && filter_query[i + 1] == '&') &&
-                                                      !(c == '|' && filter_query[i + 1] == '|'))));
-            }
-        }
-    }
-}
-
 /*size_t StringUtils::unicode_length(const std::string& bytes) {
     std::wstring_convert<std::codecvt_utf8<char32_t>, char32_t> utf8conv;
     return utf8conv.from_bytes(bytes).size();
diff --git a/test/collection_manager_test.cpp b/test/collection_manager_test.cpp
index e821e51b..3c18db44 100644
--- a/test/collection_manager_test.cpp
+++ b/test/collection_manager_test.cpp
@@ -1245,3 +1245,33 @@ TEST_F(CollectionManagerTest, CloneCollection) {
     ASSERT_EQ('-', coll2->get_token_separators().at(0));
     ASSERT_EQ('?', coll2->get_token_separators().at(1));
 }
+
+TEST(StringUtilsTest, GetReferenceCollectionNames) {
+    std::string filter_query = "";
+    std::set<std::string> reference_collection_names;
+    CollectionManager::_get_reference_collection_names(filter_query, reference_collection_names);
+    ASSERT_TRUE(reference_collection_names.empty());
+
+    filter_query = "foo:bar";
+    CollectionManager::_get_reference_collection_names(filter_query, reference_collection_names);
+    ASSERT_TRUE(reference_collection_names.empty());
+
+    filter_query = "$foo(bar:baz)";
+    std::vector<std::string> result = {"foo"};
+    CollectionManager::_get_reference_collection_names(filter_query, reference_collection_names);
+    ASSERT_EQ(1, reference_collection_names.size());
+    for (const auto &item: result) {
+        ASSERT_EQ(1, reference_collection_names.count(item));
+    }
+    reference_collection_names.clear();
+
+    filter_query = "((age: <5 || age: >10) && category:= [shoes]) &&"
+                   " $Customers(customer_id:=customer_a && (product_price:>100 && product_price:<200))";
+    result = {"Customers"};
+    CollectionManager::_get_reference_collection_names(filter_query, reference_collection_names);
+    ASSERT_EQ(1, reference_collection_names.size());
+    for (const auto &item: result) {
+        ASSERT_EQ(1, reference_collection_names.count(item));
+    }
+    reference_collection_names.clear();
+}
diff --git a/test/string_utils_test.cpp b/test/string_utils_test.cpp
index 6b931972..1ee9e6ac 100644
--- a/test/string_utils_test.cpp
+++ b/test/string_utils_test.cpp
@@ -420,33 +420,3 @@ TEST(StringUtilsTest, SplitIncludeFields) {
     tokens = {"id", "$Collection(title, pref*)", "count"};
     splitIncludeTestHelper(include_fields, tokens);
 }
-
-TEST(StringUtilsTest, GetReferenceCollectionNames) {
-    std::string filter_query = "";
-    std::set<std::string> reference_collection_names;
-    StringUtils::get_reference_collection_names(filter_query, reference_collection_names);
-    ASSERT_TRUE(reference_collection_names.empty());
-
-    filter_query = "foo:bar";
-    StringUtils::get_reference_collection_names(filter_query, reference_collection_names);
-    ASSERT_TRUE(reference_collection_names.empty());
-
-    filter_query = "$foo(bar:baz)";
-    std::vector<std::string> result = {"foo"};
-    StringUtils::get_reference_collection_names(filter_query, reference_collection_names);
-    ASSERT_EQ(1, reference_collection_names.size());
-    for (const auto &item: result) {
-        ASSERT_EQ(1, reference_collection_names.count(item));
-    }
-    reference_collection_names.clear();
-
-    filter_query = "((age: <5 || age: >10) && category:= [shoes]) &&"
-                   " $Customers(customer_id:=customer_a && (product_price:>100 && product_price:<200))";
-    result = {"Customers"};
-    StringUtils::get_reference_collection_names(filter_query, reference_collection_names);
-    ASSERT_EQ(1, reference_collection_names.size());
-    for (const auto &item: result) {
-        ASSERT_EQ(1, reference_collection_names.count(item));
-    }
-    reference_collection_names.clear();
-}