feat(transactions): add single-node transaction support with session-aware reads, commits, aborts, and transaction metrics

rust/crates/rustdb-commands/src/handlers/find_handler.rs

@@ -7,6 +7,7 @@ use rustdb_query::{QueryMatcher, sort_documents, apply_projection, distinct_valu
 
 use crate::context::{CommandContext, CursorState};
 use crate::error::{CommandError, CommandResult};
+use crate::transactions;
 
 /// Atomic counter for generating unique cursor IDs.
 static CURSOR_ID_COUNTER: AtomicI64 = AtomicI64::new(1);
@@ -80,9 +81,14 @@ pub async fn handle(
     let limit = get_i64(cmd, "limit").unwrap_or(0).max(0) as usize;
     let batch_size = get_i32(cmd, "batchSize").unwrap_or(101).max(0) as usize;
     let single_batch = get_bool(cmd, "singleBatch").unwrap_or(false);
+    let txn_id = transactions::active_transaction_id(ctx, cmd);
 
     // If the collection does not exist, return an empty cursor.
-    let exists = ctx.storage.collection_exists(db, coll).await?;
+    let exists = if txn_id.is_some() {
+        true
+    } else {
+        ctx.storage.collection_exists(db, coll).await?
+    };
     if !exists {
         return Ok(doc! {
             "cursor": {
@@ -96,7 +102,9 @@ pub async fn handle(
 
     // Try index-accelerated lookup.
     let index_key = format!("{}.{}", db, coll);
-    let docs = if let Some(idx_ref) = ctx.indexes.get(&index_key) {
+    let docs = if let Some(ref txn_id) = txn_id {
+        transactions::load_transaction_docs(ctx, txn_id, db, coll).await?
+    } else if let Some(idx_ref) = ctx.indexes.get(&index_key) {
         if let Some(candidate_ids) = idx_ref.find_candidate_ids(&filter) {
             debug!(
                 ns = %ns,
@@ -298,9 +306,14 @@ pub async fn handle_count(
     ctx: &CommandContext,
 ) -> CommandResult<Document> {
     let coll = get_str(cmd, "count").unwrap_or("unknown");
+    let txn_id = transactions::active_transaction_id(ctx, cmd);
 
     // Check collection existence.
-    let exists = ctx.storage.collection_exists(db, coll).await?;
+    let exists = if txn_id.is_some() {
+        true
+    } else {
+        ctx.storage.collection_exists(db, coll).await?
+    };
     if !exists {
         return Ok(doc! { "n": 0_i64, "ok": 1.0 });
     }
@@ -309,6 +322,23 @@ pub async fn handle_count(
     let skip = get_i64(cmd, "skip").unwrap_or(0).max(0) as usize;
     let limit = get_i64(cmd, "limit").unwrap_or(0).max(0) as usize;
 
+    if let Some(ref txn_id) = txn_id {
+        let docs = transactions::load_transaction_docs(ctx, txn_id, db, coll).await?;
+        let filtered = if query.is_empty() {
+            docs
+        } else {
+            QueryMatcher::filter(&docs, &query)
+        };
+        let mut n = filtered.len().saturating_sub(skip);
+        if limit > 0 {
+            n = n.min(limit);
+        }
+        return Ok(doc! {
+            "n": n as i64,
+            "ok": 1.0,
+        });
+    }
+
     let count: u64 = if query.is_empty() && skip == 0 && limit == 0 {
         // Fast path: use storage-level count.
         ctx.storage.count(db, coll).await?
@@ -352,15 +382,24 @@ pub async fn handle_distinct(
     let key = get_str(cmd, "key").ok_or_else(|| {
         CommandError::InvalidArgument("distinct requires a 'key' field".into())
     })?;
+    let txn_id = transactions::active_transaction_id(ctx, cmd);
 
     // Check collection existence.
-    let exists = ctx.storage.collection_exists(db, coll).await?;
+    let exists = if txn_id.is_some() {
+        true
+    } else {
+        ctx.storage.collection_exists(db, coll).await?
+    };
     if !exists {
         return Ok(doc! { "values": [], "ok": 1.0 });
     }
 
     let query = get_document(cmd, "query").cloned();
-    let docs = ctx.storage.find_all(db, coll).await?;
+    let docs = if let Some(txn_id) = txn_id {
+        transactions::load_transaction_docs(ctx, &txn_id, db, coll).await?
+    } else {
+        ctx.storage.find_all(db, coll).await?
+    };
     let values = distinct_values(&docs, key, query.as_ref());
 
     Ok(doc! {