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node_modules/sequelize/lib/dialects/mysql/query-interface.js

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+'use strict';
+
+/**
+ Returns an object that treats MySQL's inabilities to do certain queries.
+
+ @class QueryInterface
+ @static
+ @private
+ */
+
+const Promise = require('../../promise');
+const sequelizeErrors = require('../../errors');
+
+/**
+ A wrapper that fixes MySQL's inability to cleanly remove columns from existing tables if they have a foreign key constraint.
+
+ @param  {QueryInterface} qi
+ @param  {string} tableName     The name of the table.
+ @param  {string} columnName    The name of the attribute that we want to remove.
+ @param  {Object} options
+
+ @private
+ */
+function removeColumn(qi, tableName, columnName, options) {
+  options = options || {};
+
+  return qi.sequelize.query(
+    qi.QueryGenerator.getForeignKeyQuery(tableName.tableName ? tableName : {
+      tableName,
+      schema: qi.sequelize.config.database
+    }, columnName),
+    Object.assign({ raw: true }, options)
+  )
+    .then(([results]) => {
+      //Exclude primary key constraint
+      if (!results.length || results[0].constraint_name === 'PRIMARY') {
+        // No foreign key constraints found, so we can remove the column
+        return;
+      }
+      return Promise.map(results, constraint => qi.sequelize.query(
+        qi.QueryGenerator.dropForeignKeyQuery(tableName, constraint.constraint_name),
+        Object.assign({ raw: true }, options)
+      ));
+    })
+    .then(() => qi.sequelize.query(
+      qi.QueryGenerator.removeColumnQuery(tableName, columnName),
+      Object.assign({ raw: true }, options)
+    ));
+}
+
+/**
+ * @param {QueryInterface} qi
+ * @param {string} tableName
+ * @param {string} constraintName
+ * @param {Object} options
+ *
+ * @private
+ */
+function removeConstraint(qi, tableName, constraintName, options) {
+  const sql = qi.QueryGenerator.showConstraintsQuery(
+    tableName.tableName ? tableName : {
+      tableName,
+      schema: qi.sequelize.config.database
+    }, constraintName);
+
+  return qi.sequelize.query(sql, Object.assign({}, options,
+    { type: qi.sequelize.QueryTypes.SHOWCONSTRAINTS }))
+    .then(constraints => {
+      const constraint = constraints[0];
+      let query;
+      if (!constraint || !constraint.constraintType) {
+        throw new sequelizeErrors.UnknownConstraintError(
+          {
+            message: `Constraint ${constraintName} on table ${tableName} does not exist`,
+            constraint: constraintName,
+            table: tableName
+          });
+      }
+
+      if (constraint.constraintType === 'FOREIGN KEY') {
+        query = qi.QueryGenerator.dropForeignKeyQuery(tableName, constraintName);
+      } else {
+        query = qi.QueryGenerator.removeIndexQuery(constraint.tableName, constraint.constraintName);
+      }
+
+      return qi.sequelize.query(query, options);
+    });
+}
+
+exports.removeConstraint = removeConstraint;
+exports.removeColumn = removeColumn;