[WIP] Implement MERGE statement execution logic

src/75merge.js

@@ -42,9 +42,116 @@ yy.Merge.prototype.toString = function () {
 	return s;
 };
 
-yy.Merge.prototype.execute = function (databaseid, params, cb) {
-	var res = 1;
+yy.Merge.prototype.compile = function (databaseid) {
+	var self = this;
+	databaseid = self.into.databaseid || databaseid;
+	var db = alasql.databases[databaseid];
+	var targettableid = self.into.tableid;
+	var sourcetableid = self.using.tableid;
+
+	if (!db.tables[targettableid]) throw new Error("Target table '" + targettableid + "' not found");
+	if (!db.tables[sourcetableid]) throw new Error("Source table '" + sourcetableid + "' not found");
+
+	if (self.exists) self.existsfn = self.exists.map(function (ex) {
+		var nq = ex.compile(databaseid); nq.query.modifier = 'RECORDSET'; return nq;
+	});
+	if (self.queries) self.queriesfn = self.queries.map(function (q) {
+		var nq = q.compile(databaseid); nq.query.modifier = 'RECORDSET'; return nq;
+	});
+
+	var targetAlias = self.into.as || targettableid;
+	var sourceAlias = self.using.as || sourcetableid;
+
+	// Helper to evaluate expressions in context
+	var evalInContext = function (expr, targetRow, sourceRow, params) {
+		var rec = {};
+		if (targetRow) rec[targetAlias] = targetRow;
+		if (sourceRow) rec[sourceAlias] = sourceRow;
+		return new Function('rec', 'params', 'alasql', 'var y; return ' + expr.toJS('rec', ''))(rec, params, alasql);
+	};
+
+	return function (params, cb) {
+		var db = alasql.databases[databaseid];
+		if (alasql.options.autocommit && db.engineid) {
+			alasql.engines[db.engineid].loadTableData(databaseid, targettableid);
+			alasql.engines[db.engineid].loadTableData(databaseid, sourcetableid);
+		}
+
+		var targetTable = db.tables[targettableid];
+		var sourceTable = db.tables[sourcetableid];
+		targetTable.dirty = true;
+		var count = 0;
+
+		// Check if target and source rows match
+		var rowsMatch = function (t, s) {
+			return evalInContext(self.on, t, s, params);
+		};
+
+		// Execute first applicable action for a row
+		var executeAction = function (targetRow, sourceRow, isMatched, isBySource) {
+			for (var m = 0; m < self.matches.length; m++) {
+				var match = self.matches[m];
+				if (match.matched !== isMatched) continue;
+				if (isMatched && match.bysource) continue;
+				if (!isMatched && ((isBySource && !match.bysource) || (!isBySource && !match.bytarget))) continue;
+				if (match.expr && !evalInContext(match.expr, targetRow, sourceRow, params)) continue;
+
+				var action = match.action;
+				if (action.delete) return 'delete';
+				if (action.update) {
+					var rec = {}; rec[targetAlias] = targetRow; rec[sourceAlias] = sourceRow;
+					action.update.forEach(function (set) {
+						targetRow[set.column.columnid] = evalInContext(set.expression, targetRow, sourceRow, params);
+					});
+					return 'update';
+				}
+				if (action.insert) {
+					var newRow = {};
+					if (action.columns && action.values && action.values[0]) {
+						action.columns.forEach(function (col, i) {
+							if (action.values[0][i]) newRow[col.columnid] = evalInContext(action.values[0][i], null, sourceRow, params);
+						});
+					} else if (action.defaultvalues && targetTable.defaultfns) {
+						eval('newRow = {' + targetTable.defaultfns + '}');
+					}
+					if (targetTable.defaultfns) {
+						eval('var defaults = {' + targetTable.defaultfns + '}');
+						for (var k in defaults) if (!(k in newRow)) newRow[k] = defaults[k];
+					}
+					if (targetTable.insert) targetTable.insert(newRow, false, false);
+					else targetTable.data.push(newRow);
+					return 'insert';
+				}
+			}
+			return null;
+		};
+
+		// Process target rows
+		for (var i = 0; i < targetTable.data.length; i++) {
+			var targetRow = targetTable.data[i];
+			var sourceRow = sourceTable.data.find(function (s) { return rowsMatch(targetRow, s); });
+			var action = executeAction(targetRow, sourceRow, !!sourceRow, !sourceRow);
+			if (action === 'delete') { targetTable.data.splice(i--, 1); count++; }
+			else if (action === 'update') count++;
+		}
+
+		// Process unmatched source rows
+		for (var j = 0; j < sourceTable.data.length; j++) {
+			var sourceRow = sourceTable.data[j];
+			if (!targetTable.data.some(function (t) { return rowsMatch(t, sourceRow); })) {
+				if (executeAction(null, sourceRow, false, false) === 'insert') count++;
+			}
+		}
+
+		if (alasql.options.autocommit && db.engineid) {
+			alasql.engines[db.engineid].saveTableData(databaseid, targettableid);
+		}
+
+		if (cb) cb(count);
+		return count;
+	};
+};
 
-	if (cb) res = cb(res);
-	return res;
+yy.Merge.prototype.execute = function (databaseid, params, cb) {
+	return this.compile(databaseid)(params, cb);
 };

test/test236.js

@@ -46,26 +46,34 @@ describe('Test 236 MERGE', function () {
 	});
 
 	it('2. Merge', function (done) {
-		var sql = function () {
-			/*
-
-        MERGE [Target] AS T
-        USING [Source] AS S
-        ON (T.EmployeeID = S.EmployeeID) 
-        WHEN NOT MATCHED BY TARGET AND S.EmployeeName LIKE 'S%' 
-            THEN INSERT(EmployeeID, EmployeeName) VALUES(S.EmployeeID, S.EmployeeName)
-        WHEN MATCHED 
-            THEN UPDATE SET T.EmployeeName = S.EmployeeName
-        WHEN NOT MATCHED BY SOURCE AND T.EmployeeName LIKE 'S%'
-            THEN DELETE
-
-    */
-		}
-			.toString()
-			.slice(14, -3);
-		/// console.log(alasql.parse(sql).toString());
+		var sql = `
+			MERGE [Target] AS T
+			USING [Source] AS S
+			ON (T.EmployeeID = S.EmployeeID) 
+			WHEN NOT MATCHED BY TARGET AND S.EmployeeName LIKE 'S%' 
+				THEN INSERT(EmployeeID, EmployeeName) VALUES(S.EmployeeID, S.EmployeeName)
+			WHEN MATCHED 
+				THEN UPDATE SET T.EmployeeName = S.EmployeeName
+			WHEN NOT MATCHED BY SOURCE AND T.EmployeeName LIKE 'S%'
+				THEN DELETE
+		`;
+
+		// Execute the MERGE
+		var res = alasql(sql);
+
+		// Verify result count (3 rows affected: 1 insert + 2 deletes)
+		assert.equal(res, 3);
+
+		// Verify final table state
+		var target = alasql('SELECT * FROM [Target] ORDER BY EmployeeID');
+		assert.deepEqual(target, [
+			{EmployeeID: 100, EmployeeName: 'Mary'},     // Unchanged (not in source, not matching S%)
+			// 101 'Sara' deleted (not in source, matches S%)
+			// 102 'Stefano' deleted (not in source, matches S%)
+			// 103 'Bob' not inserted (in source but doesn't match S%)
+			{EmployeeID: 104, EmployeeName: 'Steve'},    // Inserted (not in target, matches S%)
+		]);
 
-		//        console.log(res);
 		done();
 	});