From 025f4bbd3a4d5cd6a1726e72400c84789d9f5d96 Mon Sep 17 00:00:00 2001
From: Harpreet Sangar <happy_san@protonmail.com>
Date: Wed, 29 Mar 2023 13:35:39 +0530
Subject: [PATCH] Add `filter_result_iterator_t::reset`.

---
 include/filter.h     |  4 ++++
 src/filter.cpp       | 42 ++++++++++++++++++++++++++++++++++++++++++
 test/filter_test.cpp | 26 ++++++++++++++++++++++++++
 3 files changed, 72 insertions(+)

diff --git a/include/filter.h b/include/filter.h
index c8d4e3b0..41ccfac8 100644
--- a/include/filter.h
+++ b/include/filter.h
@@ -94,5 +94,9 @@ public:
     /// this operation.
     void skip_to(uint32_t id);
 
+    /// Returns true if at least one id from the posting list object matches the filter.
     bool contains_atleast_one(const void* obj);
+
+    /// Returns to the initial state of the iterator.
+    void reset();
 };
diff --git a/src/filter.cpp b/src/filter.cpp
index 304799b3..d40a5564 100644
--- a/src/filter.cpp
+++ b/src/filter.cpp
@@ -544,3 +544,45 @@ bool filter_result_iterator_t::contains_atleast_one(const void *obj) {
 
     return false;
 }
+
+void filter_result_iterator_t::reset() {
+    if (filter_node->isOperator) {
+        // Reset the subtrees then apply operators to arrive at the first valid doc.
+        left_it->reset();
+        right_it->reset();
+
+        if (filter_node->filter_operator == AND) {
+            and_filter_iterators();
+        } else {
+            or_filter_iterators();
+        }
+
+        return;
+    }
+
+    const filter a_filter = filter_node->filter_exp;
+
+    bool is_referenced_filter = !a_filter.referenced_collection_name.empty();
+    if (is_referenced_filter || a_filter.field_name == "id") {
+        result_index = 0;
+        is_valid = filter_result.count > 0;
+        return;
+    }
+
+    if (!index->field_is_indexed(a_filter.field_name)) {
+        return;
+    }
+
+    field f = index->search_schema.at(a_filter.field_name);
+
+    if (f.is_string()) {
+        posting_list_iterators.clear();
+        for(auto expanded_plist: expanded_plists) {
+            delete expanded_plist;
+        }
+        expanded_plists.clear();
+
+        init();
+        return;
+    }
+}
diff --git a/test/filter_test.cpp b/test/filter_test.cpp
index 0c3687db..af7145f2 100644
--- a/test/filter_test.cpp
+++ b/test/filter_test.cpp
@@ -331,5 +331,31 @@ TEST_F(FilterTest, FilterTreeIterator) {
 
     ASSERT_TRUE(iter_plist_contains_atleast_one_test2.contains_atleast_one(&p_list1));
 
+    delete filter_tree_root;
+    filter_tree_root = nullptr;
+    filter_op = filter::parse_filter_query("tags:= [gold, silver]", coll->get_schema(), store, doc_id_prefix,
+                                           filter_tree_root);
+    ASSERT_TRUE(filter_op.ok());
+
+    auto iter_reset_test = filter_result_iterator_t(coll->get_name(), coll->_get_index(), filter_tree_root);
+    ASSERT_TRUE(iter_reset_test.init_status().ok());
+
+    expected = {0, 2, 3, 4};
+    for (auto const& i : expected) {
+        ASSERT_TRUE(iter_reset_test.valid());
+        ASSERT_EQ(i, iter_reset_test.seq_id);
+        iter_reset_test.next();
+    }
+    ASSERT_FALSE(iter_reset_test.valid());
+
+    iter_reset_test.reset();
+
+    for (auto const& i : expected) {
+        ASSERT_TRUE(iter_reset_test.valid());
+        ASSERT_EQ(i, iter_reset_test.seq_id);
+        iter_reset_test.next();
+    }
+    ASSERT_FALSE(iter_reset_test.valid());
+
     delete filter_tree_root;
 }
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