fix(core): harden extract_table_name parsing

crates/dkdc-db-core/src/db.rs

@@ -12,17 +12,42 @@ const WAL_MODE_PRAGMA: &str = "journal_mode";
 const WAL_MODE_VALUE: &str = "'wal'";
 
 /// Try to extract a table name from a simple SELECT query for PRAGMA fallback.
-/// Handles `SELECT ... FROM table_name` patterns.
+/// Handles `SELECT ... FROM table_name` patterns, including schema-qualified
+/// names (`schema.table`) and quoted identifiers (`"My Table"`).
+/// Returns `None` for subqueries and other non-simple patterns.
 fn extract_table_name(sql: &str) -> Option<String> {
     let upper = sql.to_uppercase();
     let from_idx = upper.find(" FROM ")?;
     let after_from = sql[from_idx + 6..].trim_start();
-    // Take the first word (table name), stop at whitespace, comma, semicolon, or parenthesis
-    let name: String = after_from
-        .chars()
-        .take_while(|c| c.is_alphanumeric() || *c == '_')
-        .collect();
-    if name.is_empty() { None } else { Some(name) }
+
+    // Subqueries start with '(' — bail out
+    if after_from.starts_with('(') {
+        return None;
+    }
+
+    // Handle quoted identifier: "table name"
+    let raw_name = if let Some(rest) = after_from.strip_prefix('"') {
+        let end = rest.find('"')?;
+        &rest[..end]
+    } else {
+        // Unquoted: take chars valid in identifiers (alphanumeric, underscore, dot for schema)
+        let end = after_from
+            .find(|c: char| !(c.is_alphanumeric() || c == '_' || c == '.'))
+            .unwrap_or(after_from.len());
+        &after_from[..end]
+    };
+
+    if raw_name.is_empty() {
+        return None;
+    }
+
+    // For schema-qualified names (schema.table), take the last part
+    let table = raw_name.rsplit('.').next().unwrap_or(raw_name);
+    if table.is_empty() {
+        None
+    } else {
+        Some(table.to_string())
+    }
 }
 
 /// Enable WAL mode on a connection for concurrent read+write.
@@ -177,3 +202,78 @@ impl DkdcDb {
         Ok(self.db.connect()?)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_extract_simple_table() {
+        assert_eq!(
+            extract_table_name("SELECT * FROM users"),
+            Some("users".to_string())
+        );
+    }
+
+    #[test]
+    fn test_extract_table_with_where() {
+        assert_eq!(
+            extract_table_name("SELECT id FROM orders WHERE id = 1"),
+            Some("orders".to_string())
+        );
+    }
+
+    #[test]
+    fn test_extract_schema_qualified() {
+        assert_eq!(
+            extract_table_name("SELECT * FROM myschema.mytable"),
+            Some("mytable".to_string())
+        );
+    }
+
+    #[test]
+    fn test_extract_quoted_identifier() {
+        assert_eq!(
+            extract_table_name("SELECT * FROM \"My Table\""),
+            Some("My Table".to_string())
+        );
+    }
+
+    #[test]
+    fn test_extract_quoted_with_schema() {
+        // Quoted name with dot inside quotes is treated as the full name
+        assert_eq!(
+            extract_table_name("SELECT * FROM \"my.table\""),
+            Some("table".to_string())
+        );
+    }
+
+    #[test]
+    fn test_extract_subquery_returns_none() {
+        assert_eq!(
+            extract_table_name("SELECT * FROM (SELECT id FROM users)"),
+            None
+        );
+    }
+
+    #[test]
+    fn test_extract_no_from_returns_none() {
+        assert_eq!(extract_table_name("SELECT 1 + 1"), None);
+    }
+
+    #[test]
+    fn test_extract_case_insensitive_from() {
+        assert_eq!(
+            extract_table_name("select * from events"),
+            Some("events".to_string())
+        );
+    }
+
+    #[test]
+    fn test_extract_table_with_semicolon() {
+        assert_eq!(
+            extract_table_name("SELECT * FROM users;"),
+            Some("users".to_string())
+        );
+    }
+}