Better handle discovery of nullable columns

lib/discovery.js

@@ -141,17 +141,27 @@ function mixinDiscovery(MySQL) {
   function queryColumns(owner, table) {
     var sql = null;
     if (owner) {
-      sql = paginateSQL('SELECT table_schema AS "owner", table_name AS "tableName", column_name AS "columnName", data_type AS "dataType",'
+      sql = paginateSQL('SELECT table_schema AS "owner",' +
-        + ' character_octet_length AS "dataLength", numeric_precision AS "dataPrecision", numeric_scale AS "dataScale", is_nullable AS "nullable"'
+          ' table_name AS "tableName", column_name AS "columnName",' +
-        + ' FROM information_schema.columns'
+          ' data_type AS "dataType",' +
-        + ' WHERE table_schema=\'' + owner + '\''
+          ' character_octet_length AS "dataLength",' +
-        + (table ? ' AND table_name=\'' + table + '\'' : ''),
+          ' numeric_precision AS "dataPrecision",' +
+          ' numeric_scale AS "dataScale",' +
+          ' is_nullable = \'YES\' AS "nullable"' +
+          ' FROM information_schema.columns' +
+          ' WHERE table_schema=\'' + owner + '\'' +
+          (table ? ' AND table_name=\'' + table + '\'' : ''),
           'table_name, ordinal_position', {});
     } else {
-      sql = paginateSQL('SELECT table_schema AS "owner", table_name AS "tableName", column_name AS "columnName", data_type AS "dataType",'
+      sql = paginateSQL('SELECT table_schema AS "owner",' +
-        + ' character_octet_length AS "dataLength", numeric_precision AS "dataPrecision", numeric_scale AS "dataScale", is_nullable AS "nullable"'
+          ' table_name AS "tableName", column_name AS "columnName",' +
-        + ' FROM information_schema.columns'
+          ' data_type AS "dataType",' +
-        + (table ? ' WHERE table_name=\'' + table + '\'' : ''),
+          ' character_octet_length AS "dataLength",' +
+          ' numeric_precision AS "dataPrecision",' +
+          ' numeric_scale AS "dataScale",' +
+          ' is_nullable = \'YES\' AS "nullable"' +
+          ' FROM information_schema.columns' +
+          (table ? ' WHERE table_name=\'' + table + '\'' : ''),
           'table_name, ordinal_position', {});
     }
     return sql;
@@ -178,6 +188,7 @@ function mixinDiscovery(MySQL) {
       } else {
         results.map(function (r) {
           r.type = mysqlDataTypeToJSONType(r.dataType, r.dataLength);
+          r.nullable = r.nullable ? 'Y' : 'N';
         });
         cb(err, results);
       }

test/mysql.discover.test.js

@@ -200,12 +200,14 @@ describe('Discover LDL schema from a table', function () {
       assert(schema.options.mysql.schema === 'STRONGLOOP');
       assert(schema.options.mysql.table === 'INVENTORY');
       assert(schema.properties.productId);
+      assert(schema.properties.productId.required);
       assert(schema.properties.productId.type === 'String');
       assert(schema.properties.productId.mysql.columnName === 'PRODUCT_ID');
       assert(schema.properties.locationId);
       assert(schema.properties.locationId.type === 'String');
       assert(schema.properties.locationId.mysql.columnName === 'LOCATION_ID');
       assert(schema.properties.available);
+      assert(schema.properties.available.required === false);
       assert(schema.properties.available.type === 'Number');
       assert(schema.properties.total);
       assert(schema.properties.total.type === 'Number');