chore: de-flak mysql/mariadb test

src/connectors/__tests__/mariadb.integration.test.ts

@@ -222,20 +222,15 @@ describe('MariaDB Connector Integration Tests', () => {
     });
 
     it('should handle MariaDB auto-increment properly', async () => {
-      const insertResult = await mariadbTest.connector.executeSQL(
-        "INSERT INTO users (name, email, age) VALUES ('Auto Inc Test', 'autoinc@example.com', 40)",
-        {}
-      );
-
-      expect(insertResult).toBeDefined();
-
-      const selectResult = await mariadbTest.connector.executeSQL(
-        'SELECT LAST_INSERT_ID() as last_id',
+      // Execute INSERT and SELECT LAST_INSERT_ID() in a single call to ensure same connection
+      const result = await mariadbTest.connector.executeSQL(
+        "INSERT INTO users (name, email, age) VALUES ('Auto Inc Test', 'autoinc@example.com', 40); SELECT LAST_INSERT_ID() as last_id",
         {}
       );
-
-      expect(selectResult.rows).toHaveLength(1);
-      expect(Number(selectResult.rows[0].last_id)).toBeGreaterThan(0);
+
+      expect(result).toBeDefined();
+      expect(result.rows).toHaveLength(1);
+      expect(Number(result.rows[0].last_id)).toBeGreaterThan(0);
     });
 
     it('should work with MariaDB-specific functions', async () => {

src/connectors/__tests__/mysql.integration.test.ts

@@ -213,20 +213,15 @@ describe('MySQL Connector Integration Tests', () => {
     });
 
     it('should handle MySQL auto-increment properly', async () => {
-      const insertResult = await mysqlTest.connector.executeSQL(
-        "INSERT INTO users (name, email, age) VALUES ('Auto Inc Test', 'autoinc@example.com', 40)",
-        {}
-      );
-
-      expect(insertResult).toBeDefined();
-
-      const selectResult = await mysqlTest.connector.executeSQL(
-        'SELECT LAST_INSERT_ID() as last_id',
+      // Execute INSERT and SELECT LAST_INSERT_ID() in a single call to ensure same connection
+      const result = await mysqlTest.connector.executeSQL(
+        "INSERT INTO users (name, email, age) VALUES ('Auto Inc Test', 'autoinc@example.com', 40); SELECT LAST_INSERT_ID() as last_id",
         {}
       );
-
-      expect(selectResult.rows).toHaveLength(1);
-      expect(Number(selectResult.rows[0].last_id)).toBeGreaterThan(0);
+
+      expect(result).toBeDefined();
+      expect(result.rows).toHaveLength(1);
+      expect(Number(result.rows[0].last_id)).toBeGreaterThan(0);
     });
 
     it('should work with MySQL-specific functions', async () => {

src/connectors/mariadb/index.ts

@@ -13,6 +13,7 @@ import {
 import { SafeURL } from "../../utils/safe-url.js";
 import { obfuscateDSNPassword } from "../../utils/dsn-obfuscate.js";
 import { SQLRowLimiter } from "../../utils/sql-row-limiter.js";
+import { parseQueryResults } from "../../utils/multi-statement-result-parser.js";
 
 /**
  * MariaDB DSN Parser
@@ -474,6 +475,9 @@ export class MariaDBConnector implements Connector {
       throw new Error("Not connected to database");
     }
 
+    // Get a dedicated connection from the pool to ensure session consistency
+    // This is critical for session-specific features like LAST_INSERT_ID()
+    const conn = await this.pool.getConnection();
     try {
       // Apply maxRows limit to SELECT queries if specified
       let processedSQL = sql;
@@ -482,49 +486,29 @@ export class MariaDBConnector implements Connector {
         const statements = sql.split(';')
           .map(statement => statement.trim())
           .filter(statement => statement.length > 0);
-        
-        const processedStatements = statements.map(statement => 
+
+        const processedStatements = statements.map(statement =>
           SQLRowLimiter.applyMaxRows(statement, options.maxRows)
         );
-        
+
         processedSQL = processedStatements.join('; ');
         if (sql.trim().endsWith(';')) {
           processedSQL += ';';
         }
       }
 
-      // Use pool.query - MariaDB driver returns rows directly for single statements
-      const results = await this.pool.query(processedSQL) as any;
-
-      // MariaDB driver returns different formats:
-      // - Single statement: returns rows array directly
-      // - Multiple statements: returns array of results (when multipleStatements is true)
-
-      if (Array.isArray(results)) {
-        // Check if this looks like multiple statement results
-        // Multiple statements return an array where each element might be an array of results
-        if (results.length > 0 && Array.isArray(results[0]) && results[0].length > 0) {
-          // This might be multiple statement results - flatten them
-          let allRows: any[] = [];
-
-          for (const result of results) {
-            if (Array.isArray(result)) {
-              allRows.push(...result);
-            }
-          }
-
-          return { rows: allRows };
-        } else {
-          // Single statement result - results is the rows array
-          return { rows: results };
-        }
-      } else {
-        // Non-array result (like for INSERT/UPDATE/DELETE without RETURNING)
-        return { rows: [] };
-      }
+      // Use dedicated connection - MariaDB driver returns rows directly for single statements
+      const results = await conn.query(processedSQL) as any;
+
+      // Parse results using shared utility that handles both single and multi-statement queries
+      const rows = parseQueryResults(results);
+      return { rows };
     } catch (error) {
       console.error("Error executing query:", error);
       throw error;
+    } finally {
+      // Always release the connection back to the pool
+      conn.release();
     }
   }
 }

src/connectors/mysql/index.ts

@@ -13,6 +13,7 @@ import {
 import { SafeURL } from "../../utils/safe-url.js";
 import { obfuscateDSNPassword } from "../../utils/dsn-obfuscate.js";
 import { SQLRowLimiter } from "../../utils/sql-row-limiter.js";
+import { parseQueryResults } from "../../utils/multi-statement-result-parser.js";
 
 /**
  * MySQL DSN Parser
@@ -471,6 +472,9 @@ export class MySQLConnector implements Connector {
       throw new Error("Not connected to database");
     }
 
+    // Get a dedicated connection from the pool to ensure session consistency
+    // This is critical for session-specific features like LAST_INSERT_ID()
+    const conn = await this.pool.getConnection();
     try {
       // Apply maxRows limit to SELECT queries if specified
       let processedSQL = sql;
@@ -479,50 +483,33 @@ export class MySQLConnector implements Connector {
         const statements = sql.split(';')
           .map(statement => statement.trim())
           .filter(statement => statement.length > 0);
-        
-        const processedStatements = statements.map(statement => 
+
+        const processedStatements = statements.map(statement =>
           SQLRowLimiter.applyMaxRows(statement, options.maxRows)
         );
-        
+
         processedSQL = processedStatements.join('; ');
         if (sql.trim().endsWith(';')) {
           processedSQL += ';';
         }
       }
 
-      // Use pool.query with multipleStatements: true support
-      const results = await this.pool.query(processedSQL) as any;
-
-      // MySQL2 with multipleStatements returns:
-      // - Single statement: [rows, fields] 
-      // - Multiple statements: [array_of_results, fields] where array_of_results contains [rows, fields] for each statement
-
+      // Use dedicated connection with multipleStatements: true support
+      const results = await conn.query(processedSQL) as any;
+
+      // MySQL2 returns results in format [rows, fields]
+      // Extract the first element which contains the actual row data
       const [firstResult] = results;
-
-      // Check if this is a multi-statement result
-      if (Array.isArray(firstResult) && firstResult.length > 0 && 
-          Array.isArray(firstResult[0])) {
-        // Multiple statements - firstResult is an array of results  
-        let allRows: any[] = [];
-
-        for (const result of firstResult) {
-          // Each result is either a ResultSetHeader object (for INSERT/UPDATE/DELETE) 
-          // or an array of rows (for SELECT)
-          if (Array.isArray(result)) {
-            // This is a rows array from a SELECT query
-            allRows.push(...result);
-          }
-          // Skip non-array results (ResultSetHeader objects)
-        }
-
-        return { rows: allRows };
-      } else {
-        // Single statement - firstResult is the rows array directly
-        return { rows: Array.isArray(firstResult) ? firstResult : [] };
-      }
+
+      // Parse results using shared utility that handles both single and multi-statement queries
+      const rows = parseQueryResults(firstResult);
+      return { rows };
     } catch (error) {
       console.error("Error executing query:", error);
       throw error;
+    } finally {
+      // Always release the connection back to the pool
+      conn.release();
     }
   }
 }

src/utils/multi-statement-result-parser.ts

@@ -0,0 +1,93 @@
+/**
+ * Multi-Statement Result Parser Utility
+ *
+ * Provides shared logic for parsing multi-statement SQL execution results
+ * from different database drivers (MariaDB, MySQL2) that have similar but
+ * slightly different result formats.
+ */
+
+/**
+ * Checks if an element is a metadata object from INSERT/UPDATE/DELETE operations
+ * rather than a row array from SELECT queries.
+ *
+ * Different drivers use different property names for metadata:
+ * - MariaDB: affectedRows, warningStatus, insertId
+ * - MySQL2: affectedRows, insertId, fieldCount, ResultSetHeader type
+ */
+function isMetadataObject(element: any): boolean {
+  if (!element || typeof element !== 'object' || Array.isArray(element)) {
+    return false;
+  }
+
+  // Check for common metadata properties that indicate this is not a row array
+  return 'affectedRows' in element ||
+         'insertId' in element ||
+         'fieldCount' in element ||
+         'warningStatus' in element;
+}
+
+/**
+ * Checks if results appear to be from a multi-statement query.
+ *
+ * Multi-statement results are arrays containing mixed types:
+ * - Metadata objects (from INSERT/UPDATE/DELETE)
+ * - Arrays of rows (from SELECT queries)
+ */
+function isMultiStatementResult(results: any): boolean {
+  if (!Array.isArray(results) || results.length === 0) {
+    return false;
+  }
+
+  const firstElement = results[0];
+
+  // If first element is metadata or an array, it's a multi-statement result
+  return isMetadataObject(firstElement) || Array.isArray(firstElement);
+}
+
+/**
+ * Extracts row arrays from multi-statement results, filtering out metadata objects.
+ *
+ * @param results - The raw results from a multi-statement query
+ * @returns Array containing only the rows from SELECT queries
+ */
+export function extractRowsFromMultiStatement(results: any): any[] {
+  if (!Array.isArray(results)) {
+    return [];
+  }
+
+  const allRows: any[] = [];
+
+  for (const result of results) {
+    if (Array.isArray(result)) {
+      // This is a row array from a SELECT query - add all rows
+      allRows.push(...result);
+    }
+    // Skip metadata objects from INSERT/UPDATE/DELETE
+  }
+
+  return allRows;
+}
+
+/**
+ * Parses database query results, handling both single and multi-statement queries.
+ *
+ * This function unifies the result parsing logic for MariaDB and MySQL2 drivers,
+ * which have similar but slightly different result formats.
+ *
+ * @param results - Raw results from the database driver
+ * @returns Array of row objects from SELECT queries
+ */
+export function parseQueryResults(results: any): any[] {
+  // Handle non-array results (e.g., from INSERT/UPDATE/DELETE without RETURNING)
+  if (!Array.isArray(results)) {
+    return [];
+  }
+
+  // Check if this is a multi-statement result
+  if (isMultiStatementResult(results)) {
+    return extractRowsFromMultiStatement(results);
+  }
+
+  // Single statement result - results is the rows array directly
+  return results;
+}