fix: add type fallback for MySQL to prevent all-NULL display (#40)

Add i32/i16 type decoding and try_get_unchecked fallback to
mysql_value_to_json(), fixing all columns showing NULL on older
MySQL versions (e.g. 5.6) where sqlx type-checked decoding fails.

crates/dbx-core/src/db/mysql.rs

@@ -132,6 +132,8 @@ fn mysql_value_to_json(row: &MySqlRow, idx: usize, type_name: &str) -> serde_jso
         .map(serde_json::Value::String)
         .or_else(|_| row.try_get::<i64, _>(idx).map(super::safe_i64_to_json))
         .or_else(|_| row.try_get::<u64, _>(idx).map(super::safe_u64_to_json))
+        .or_else(|_| row.try_get::<i32, _>(idx).map(|v| serde_json::Value::Number(v.into())))
+        .or_else(|_| row.try_get::<i16, _>(idx).map(|v| serde_json::Value::Number(v.into())))
         .or_else(|_| {
             row.try_get::<f64, _>(idx).map(|v| {
                 serde_json::Number::from_f64(v).map(serde_json::Value::Number).unwrap_or(serde_json::Value::Null)
@@ -142,6 +144,11 @@ fn mysql_value_to_json(row: &MySqlRow, idx: usize, type_name: &str) -> serde_jso
             row.try_get::<Vec<u8>, _>(idx).map(|b| serde_json::Value::String(String::from_utf8_lossy(&b).to_string()))
         })
         .or_else(|e| mysql_temporal_to_json_value(row, idx).ok_or(e))
+        .or_else(|_| row.try_get_unchecked::<String, _>(idx).map(serde_json::Value::String))
+        .or_else(|_| {
+            row.try_get_unchecked::<Vec<u8>, _>(idx)
+                .map(|b| serde_json::Value::String(String::from_utf8_lossy(&b).to_string()))
+        })
         .unwrap_or(serde_json::Value::Null)
 }
 

crates/dbx-core/src/db/oracle_driver.rs

@@ -22,16 +22,6 @@ pub async fn connect(
         .map_err(|_| format!("Oracle connection timed out ({CONNECTION_TIMEOUT_SECS}s)"))?
         .map_err(|e| format!("Oracle connection failed: {e}"))?;
 
-    // Verify connection works with a simple query
-    log::info!("[oracle] connect: verifying with SELECT 1 FROM DUAL...");
-    conn.query("SELECT 1 FROM DUAL", &[]).await.map_err(|e| format!("Oracle connection verification failed: {e}"))?;
-    log::info!("[oracle] connect: verification OK, testing multi-row...");
-    let r = conn
-        .query("SELECT username FROM all_users ORDER BY username", &[])
-        .await
-        .map_err(|e| format!("Oracle multi-row test failed: {e}"))?;
-    log::info!("[oracle] connect: multi-row OK, {} rows", r.rows.len());
-
     Ok(conn)
 }
 
@@ -270,6 +260,11 @@ pub async fn list_triggers(conn: &OracleClient, schema: &str, table: &str) -> Re
 pub async fn execute_query(conn: &OracleClient, sql: &str) -> Result<QueryResult, String> {
     let start = Instant::now();
     let sql = sql.trim().trim_end_matches(';');
+
+    // Rewrite FETCH FIRST N ROWS ONLY → ROWNUM for Oracle 11g compatibility
+    let sql = rewrite_fetch_first(sql);
+    let sql = sql.as_ref();
+
     let trimmed = sql.to_uppercase();
     log::debug!("[oracle] execute_query: sql={}", &sql[..sql.len().min(200)]);
 
@@ -324,3 +319,17 @@ pub async fn execute_query(conn: &OracleClient, sql: &str) -> Result<QueryResult
         }
     }
 }
+
+fn rewrite_fetch_first(sql: &str) -> std::borrow::Cow<'_, str> {
+    let upper = sql.to_uppercase();
+    if let Some(pos) = upper.find("FETCH FIRST") {
+        if let Some(end) = upper[pos..].find("ROWS ONLY") {
+            let between = sql[pos + 11..pos + end].trim();
+            if let Ok(n) = between.parse::<u64>() {
+                let base = sql[..pos].trim_end();
+                return std::borrow::Cow::Owned(format!("SELECT * FROM ({base}) WHERE ROWNUM <= {n}"));
+            }
+        }
+    }
+    std::borrow::Cow::Borrowed(sql)
+}