From bccb87e96e44b73c6617daa8704eb0a089109b81 Mon Sep 17 00:00:00 2001
From: Pascal Seitz <pascal.seitz@gmail.com>
Date: Fri, 10 Feb 2023 15:12:05 +0800
Subject: [PATCH] fix: auto downgrade index record option, instead of vint
 error

Prev: thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: IoError(Custom { kind: InvalidData, error: "Reach end of buffer while reading VInt" })', src/main.rs:46:14
Now: Automatic downgrade to next available level
---
 src/core/inverted_index_reader.rs  |  2 ++
 src/query/term_query/term_query.rs |  5 +++--
 src/schema/index_record_option.rs  | 15 +++++++++++++++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/core/inverted_index_reader.rs b/src/core/inverted_index_reader.rs
index b986b74959..d9fe312666 100644
--- a/src/core/inverted_index_reader.rs
+++ b/src/core/inverted_index_reader.rs
@@ -135,6 +135,8 @@ impl InvertedIndexReader {
         term_info: &TermInfo,
         option: IndexRecordOption,
     ) -> io::Result<SegmentPostings> {
+        let option = option.downgrade(self.record_option);
+
         let block_postings = self.read_block_postings_from_terminfo(term_info, option)?;
         let position_reader = {
             if option.has_positions() {
diff --git a/src/query/term_query/term_query.rs b/src/query/term_query/term_query.rs
index 89b3a7e14e..32e0ee7cfd 100644
--- a/src/query/term_query/term_query.rs
+++ b/src/query/term_query/term_query.rs
@@ -104,14 +104,15 @@ impl TermQuery {
             }
         };
         let scoring_enabled = enable_scoring.is_scoring_enabled();
-        let index_record_option = if scoring_enabled {
+        let requested_index_record_option = if scoring_enabled {
             self.index_record_option
         } else {
             IndexRecordOption::Basic
         };
+
         Ok(TermWeight::new(
             self.term.clone(),
-            index_record_option,
+            requested_index_record_option,
             bm25_weight,
             scoring_enabled,
         ))
diff --git a/src/schema/index_record_option.rs b/src/schema/index_record_option.rs
index 9550549c56..e44638c320 100644
--- a/src/schema/index_record_option.rs
+++ b/src/schema/index_record_option.rs
@@ -1,5 +1,7 @@
 use serde::{Deserialize, Serialize};
 
+use crate::TantivyError;
+
 /// `IndexRecordOption` describes an amount information associated
 /// with a given indexed field.
 ///
@@ -49,4 +51,17 @@ impl IndexRecordOption {
             IndexRecordOption::WithFreqsAndPositions => true,
         }
     }
+
+    /// Downgrades to the next level if provided `IndexRecordOption` is unavailable.
+    pub fn downgrade(&self, other: IndexRecordOption) -> IndexRecordOption {
+        use IndexRecordOption::*;
+
+        match (other, self) {
+            (WithFreqsAndPositions, WithFreqsAndPositions) => WithFreqsAndPositions,
+            (WithFreqs, WithFreqs) => WithFreqs,
+            (WithFreqsAndPositions, WithFreqs) => WithFreqs,
+            (WithFreqs, WithFreqsAndPositions) => WithFreqs,
+            _ => Basic,
+        }
+    }
 }