fix: implement cascading deletion checks for MySQL, PostgreSQL, and SQLite connectors

Author: kulikp1

adminforth/dataConnectors/mysql.ts

@@ -76,6 +76,28 @@ class MysqlConnector extends AdminForthBaseConnector implements IAdminForthDataS
 
   async discoverFields(resource) {
     const [results] = await this.client.execute("SHOW COLUMNS FROM " + resource.table);
+    const [fkResults] = await this.client.execute(`
+      SELECT
+        kcu.TABLE_NAME AS child_table,
+        kcu.COLUMN_NAME AS column_name,
+        rc.DELETE_RULE AS delete_rule
+      FROM information_schema.KEY_COLUMN_USAGE kcu
+      JOIN information_schema.REFERENTIAL_CONSTRAINTS rc
+        ON kcu.CONSTRAINT_NAME = rc.CONSTRAINT_NAME
+        AND kcu.CONSTRAINT_SCHEMA = rc.CONSTRAINT_SCHEMA
+      WHERE kcu.REFERENCED_TABLE_NAME = ?
+        AND kcu.TABLE_SCHEMA = DATABASE()
+    `, [resource.table]);
+
+    const fkMap: Record<string, { cascade: boolean; childTable: string }> = {};
+    for (const fk of fkResults as any[]) {
+      fkMap[String(fk.column_name)] = {
+        cascade: String(fk.delete_rule).toUpperCase() === 'CASCADE',
+        childTable: fk.child_table
+      };
+      if (fkMap[fk.column_name].cascade) {
+        afLogger.warn(`The database has ON DELETE CASCADE, which may conflict with adminForth cascade deletion and upload logic. Please remove it.`);      }
+      }
     const fieldTypes = {};
     results.forEach((row) => {
       const field: any = {};

adminforth/dataConnectors/postgres.ts

@@ -69,9 +69,51 @@ class PostgresConnector extends AdminForthBaseConnector implements IAdminForthDa
         return res.rows.map(row => ({ name: row.column_name, sampleValue: sampleRow[row.column_name] }));
       }
 
+    private async getPgFkCascadeMap(
+        tableName: string,
+        schema = 'public'
+    ): Promise<Record<string, { cascade: boolean; targetTable: string }>> {
+        const res = await this.client.query(
+            `
+            SELECT
+                att.attname AS column_name,
+                rel.relname AS child_table,
+                p.relname AS parent_table,
+                con.confdeltype AS confdeltype
+            FROM pg_constraint con
+            JOIN pg_class rel ON rel.oid = con.conrelid
+            JOIN pg_namespace nsp ON nsp.oid = rel.relnamespace
+            JOIN LATERAL unnest(con.conkey) WITH ORDINALITY AS k(attnum, ord) ON TRUE
+            JOIN pg_attribute att 
+                ON att.attrelid = con.conrelid AND att.attnum = k.attnum
+            JOIN pg_class p ON p.oid = con.confrelid
+            WHERE con.contype = 'f'
+            AND nsp.nspname = $2
+            AND p.relname = $1
+            `,
+            [tableName, schema]
+        );
+        
+        const fkMap: Record<string, { cascade: boolean; targetTable: string }> = {};
+
+        for (const row of res.rows) {
+            fkMap[row.column_name.toLowerCase()] = {
+                cascade: row.confdeltype === 'c',
+                targetTable: row.parent_table,
+            };
+        }
+        return fkMap;
+    }
+
     async discoverFields(resource) {
 
         const tableName = resource.table;
+        const fkMap = await this.getPgFkCascadeMap(tableName);
+        const hasCascade = Object.values(fkMap).some(fk => fk.cascade);
+        const cascadeWarningShownMap: Record<string, boolean> = {};
+        if (hasCascade && !cascadeWarningShownMap[tableName]) {
+            afLogger.warn(`The database has ON DELETE CASCADE, which may conflict with adminForth cascade deletion and upload logic. Please remove it.`);
+        }
         const stmt = await this.client.query(`
         SELECT
             a.attname AS name,

adminforth/dataConnectors/sqlite.ts

@@ -42,6 +42,12 @@ class SQLiteConnector extends AdminForthBaseConnector implements IAdminForthData
         const tableName = resource.table;
         const stmt = this.client.prepare(`PRAGMA table_info(${tableName})`);
         const rows = await stmt.all();
+        const fkStmt = this.client.prepare(`PRAGMA foreign_key_list(${tableName})`);
+        const fkRows = await fkStmt.all();
+        const fkMap: { [colName: string]: boolean } = {};
+        fkRows.forEach(fk => {
+            fkMap[fk.from] = fk.on_delete?.toUpperCase() === 'CASCADE';
+        });
         const fieldTypes = {};
         rows.forEach((row) => {
           const field: any = {};
@@ -86,6 +92,11 @@ class SQLiteConnector extends AdminForthBaseConnector implements IAdminForthData
           field._baseTypeDebug = baseType;
           field.required = row.notnull == 1;
           field.primaryKey = row.pk == 1;
+
+          field.cascade = fkMap[row.name] || false;
+          if (field.cascade) {
+            afLogger.warn(`The database has ON DELETE CASCADE, which may conflict with adminForth cascade deletion and upload logic. Please remove it.`);
+          }
           field.default = row.dflt_value;
           fieldTypes[row.name] = field
         });