fix: use HashMap for MemTable

Author: michaelmior

src/db.rs

@@ -312,10 +312,11 @@ impl Collection {
         let mut sources: Vec<SourceIterator> = Vec::new();
 
         // 1. MemTable Iterator (Priority 0 - Highest)
-        let mem_iter = self
-            .memtable
-            .documents
-            .iter()
+        // Must sort because MemTable now uses HashMap
+        let mut mem_docs: Vec<_> = self.memtable.documents.iter().collect();
+        mem_docs.sort_by_key(|(k, _)| *k);
+        let mem_iter = mem_docs
+            .into_iter()
             .map(|(k, v)| ExecutionResult::Value(k.clone(), v.clone()));
 
         sources.push((Box::new(mem_iter) as Box<dyn Iterator<Item = ExecutionResult>>).peekable());

src/storage.rs

@@ -1,10 +1,10 @@
 use crate::Value;
 use crate::jstable::JSTable;
 use crate::schema::{Schema, SchemaExt, infer_schema};
-use std::collections::BTreeMap;
+use std::collections::{BTreeMap, HashMap};
 
 pub struct MemTable {
-    pub documents: BTreeMap<String, Value>,
+    pub documents: HashMap<String, Value>,
     schema: Schema,
 }
 
@@ -17,7 +17,7 @@ impl Default for MemTable {
 impl MemTable {
     pub fn new() -> Self {
         MemTable {
-            documents: BTreeMap::new(),
+            documents: HashMap::new(),
             schema: Schema::default(),
         }
     }
@@ -40,7 +40,11 @@ impl MemTable {
             .duration_since(std::time::UNIX_EPOCH)
             .unwrap()
             .as_millis() as u64;
-        let jstable = JSTable::new(timestamp, collection, self.schema, self.documents);
+
+        // Sort documents by ID for JSTable
+        let sorted_docs: BTreeMap<String, Value> = self.documents.into_iter().collect();
+
+        let jstable = JSTable::new(timestamp, collection, self.schema, sorted_docs);
         jstable.write(path, index_threshold)
     }