Add rough handling for automatic foreign keys

This handles basic creating/dropping of FKs based on model relations

lib/migration.js

@@ -42,13 +42,15 @@ function mixinMigration(MySQL, mysql) {
       var table = self.tableEscaped(model);
       self.execute('SHOW FIELDS FROM ' + table, function(err, fields) {
         self.execute('SHOW INDEXES FROM ' + table, function(err, indexes) {
+          self.discoverForeignKeys(model, {}, function(discoverErr, foreignKeys) {
             if (!err && fields && fields.length) {
-            self.alterTable(model, fields, indexes, done);
+              self.alterTable(model, fields, indexes, foreignKeys, done);
             } else {
               self.createTable(model, done);
             }
           });
         });
+      });
     }, cb);
   };
 
@@ -93,7 +95,8 @@ function mixinMigration(MySQL, mysql) {
       var table = self.tableEscaped(model);
       self.execute('SHOW FIELDS FROM ' + table, function(err, fields) {
         self.execute('SHOW INDEXES FROM ' + table, function(err, indexes) {
-          self.alterTable(model, fields, indexes, function(err, needAlter) {
+          self.discoverForeignKeys(model, {}, function(discoverErr, foreignKeys) {
+            self.alterTable(model, fields, indexes, foreignKeys, function(err, needAlter) {
               if (err) {
                 return done(err);
               } else {
@@ -103,6 +106,7 @@ function mixinMigration(MySQL, mysql) {
             }, true);
           });
         });
+      });
     }, function(err) {
       if (err) {
         return err;
@@ -111,7 +115,7 @@ function mixinMigration(MySQL, mysql) {
     });
   };
 
-  MySQL.prototype.alterTable = function(model, actualFields, actualIndexes, done, checkOnly) {
+  MySQL.prototype.alterTable = function(model, actualFields, actualIndexes, actualFks, done, checkOnly) {
     var self = this;
     var m = this.getModelDefinition(model);
     var propNames = Object.keys(m.properties).filter(function(name) {
@@ -121,6 +125,10 @@ function mixinMigration(MySQL, mysql) {
     var indexNames = Object.keys(indexes).filter(function(name) {
       return !!m.settings.indexes[name];
     });
+    var newFks = m.settings.foreignKeys || {};
+    var newFkNames = Object.keys(newFks).filter(function(name) {
+      return !!m.settings.foreignKeys[name];
+    });
     var sql = [];
     var ai = {};
 
@@ -159,6 +167,35 @@ function mixinMigration(MySQL, mysql) {
       }
     });
 
+    //drop foreign keys for removed fields
+    if (actualFks) {
+      var removedFks = [];
+      actualFks.forEach(function(fk) {
+        var needsToDrop = false;
+        var newFk = newFks[fk.fkName];
+        if (newFk) {
+          var fkCol = expectedColName(newFk.foreignKey);
+          var fkRefKey = expectedColNameForModel(newFk.entityKey, newFk.entity);
+          var fkRefTable = newFk.entity.name; //TODO check for mysql name
+          needsToDrop = fkCol != fk.fkColumnName ||
+                        fkRefKey != fk.pkColumnName ||
+                        fkRefTable != fk.pkTableName;
+        } else {
+          needsToDrop = true;
+        }
+
+        if (needsToDrop) {
+          sql.push('DROP FOREIGN KEY ' + fk.fkName);
+          removedFks.push(fk); //keep track that we removed these
+        }
+      });
+
+      //update out list of existing keys by removing dropped keys
+      actualFks = actualFks.filter(function(k) {
+        return removedFks.indexOf(k) == -1;
+      });
+    }
+
     // drop columns
     if (actualFields) {
       actualFields.forEach(function(f) {
@@ -177,6 +214,8 @@ function mixinMigration(MySQL, mysql) {
     aiNames.forEach(function(indexName) {
       if (indexName === 'PRIMARY' ||
         (m.properties[indexName] && self.id(model, indexName))) return;
+
+      if (newFkNames.indexOf(indexName) > -1) return; //this index is from an FK
       if (indexNames.indexOf(indexName) === -1 && !m.properties[indexName] ||
         m.properties[indexName] && !m.properties[indexName].index) {
         sql.push('DROP INDEX ' + self.client.escapeId(indexName));
@@ -293,6 +332,16 @@ function mixinMigration(MySQL, mysql) {
       }
     });
 
+    //add new foreign keys
+    if (newFkNames.length) {
+      //TODO validate that these are in the same DB, etc.
+      var oldKeyNames = actualFks.map(function(oldKey) { return oldKey.fkName; });
+      newFkNames.filter(function(key) { return !~oldKeyNames.indexOf(key); })
+        .forEach(function(key) {
+          sql.push(self.buildForeignKeyDefinition(m, key));
+        });
+    }
+
     if (sql.length) {
       var query = 'ALTER TABLE ' + self.tableEscaped(model) + ' ' +
         sql.join(',\n');
@@ -336,7 +385,11 @@ function mixinMigration(MySQL, mysql) {
     }
 
     function expectedColName(propName) {
-      var mysql = m.properties[propName].mysql;
+      return expectedColNameForModel(propName, m);
+    }
+
+    function expectedColNameForModel(propName, modelToCheck) {
+      var mysql = modelToCheck.properties[propName].mysql;
       if (typeof mysql === 'undefined') {
         return propName;
       }
@@ -348,6 +401,18 @@ function mixinMigration(MySQL, mysql) {
     }
   };
 
+  MySQL.prototype.buildForeignKeyDefinition = function(model, keyName) {
+    var fk = model.settings.foreignKeys[keyName];
+    if (fk) {
+      //TODO verify that the other model in the same DB
+      return ' ADD CONSTRAINT ' + this.client.escapeId(fk.name) +
+        ' FOREIGN KEY (' + fk.foreignKey + ')' +
+        ' REFERENCES ' + this.tableEscaped(fk.entity.name) +
+        '(' + this.client.escapeId(fk.entityKey) + ')';
+    }
+    return '';
+  };
+
   MySQL.prototype.buildColumnDefinitions =
     MySQL.prototype.propertiesSQL = function(model) {
       var self = this;