fix: change IO related rust unwrap to ? (#48333)

issue: https://github.com/milvus-io/milvus/issues/48320

---------

Signed-off-by: SpadeA <tangchenjie1210@gmail.com>

internal/core/thirdparty/tantivy/tantivy-binding/src/index_ngram_writer.rs

@@ -45,11 +45,10 @@ impl IndexWriterWrapper {
 
         let (schema, field) = build_ngram_schema(field_name);
 
-        let index = Index::create_in_dir(path, schema).unwrap();
+        let index = Index::create_in_dir(path, schema)?;
         index.tokenizers().register(NGRAM_TOKENIZER, tokenizer);
-        let index_writer = index
-            .writer_with_num_threads(num_threads, overall_memory_budget_in_bytes)
-            .unwrap();
+        let index_writer =
+            index.writer_with_num_threads(num_threads, overall_memory_budget_in_bytes)?;
 
         Ok(IndexWriterWrapper::V7(IndexWriterWrapperImpl {
             field,

internal/core/thirdparty/tantivy/tantivy-binding/src/index_writer_v5/index_writer_text.rs

@@ -43,12 +43,11 @@ impl IndexWriterWrapperImpl {
         let index = if in_ram {
             Index::create_in_ram(schema)
         } else {
-            Index::create_in_dir(path, schema).unwrap()
+            Index::create_in_dir(path, schema)?
         };
         index.tokenizers().register(tokenizer_name, tokenizer);
-        let index_writer = index
-            .writer_with_num_threads(num_threads, overall_memory_budget_in_bytes)
-            .unwrap();
+        let index_writer =
+            index.writer_with_num_threads(num_threads, overall_memory_budget_in_bytes)?;
 
         Ok(IndexWriterWrapperImpl {
             field,

internal/core/thirdparty/tantivy/tantivy-binding/src/index_writer_v7/index_writer_text.rs

@@ -44,12 +44,11 @@ impl IndexWriterWrapperImpl {
         let index = if in_ram {
             Index::create_in_ram(schema)
         } else {
-            Index::create_in_dir(path, schema).unwrap()
+            Index::create_in_dir(path, schema)?
         };
         index.tokenizers().register(analyzer_name, analyzer);
-        let index_writer = index
-            .writer_with_num_threads(num_threads, overall_memory_budget_in_bytes)
-            .unwrap();
+        let index_writer =
+            index.writer_with_num_threads(num_threads, overall_memory_budget_in_bytes)?;
 
         Ok(IndexWriterWrapperImpl {
             field,

internal/core/thirdparty/tantivy/tantivy-binding/src/util.rs

@@ -22,7 +22,7 @@ pub fn index_exist(path: &str) -> bool {
         );
         return false;
     };
-    let exists = Index::exists(&dir).unwrap();
+    let exists = Index::exists(&dir).unwrap_or(false);
     if !exists {
         init_log();
         let files: Vec<_> = std::fs::read_dir(path)