[sql lab] option to disable cross schema search (#4551)

* [sql lab] disable cross schema search

This is killing our metastore as people type it emits large
all-table-dump as they hit the keystroke. It never returns as it times
out and hammers the poor metastore.

Also some improvements around the disabling the table select on the left
panel and having the table name not be sticky.

* typo

superset/assets/javascripts/SqlLab/components/SqlEditorLeftBar.jsx

@@ -16,6 +16,7 @@ const propTypes = {
   height: PropTypes.number.isRequired,
   tables: PropTypes.array,
   actions: PropTypes.object,
+  database: PropTypes.object,
 };
 
 const defaultProps = {
@@ -139,6 +140,14 @@ class SqlEditorLeftBar extends React.PureComponent {
   render() {
     const shouldShowReset = window.location.search === '?reset=1';
     const tableMetaDataHeight = this.props.height - 130; // 130 is the height of the selects above
+    let tableSelectPlaceholder;
+    let tableSelectDisabled = false;
+    if (this.props.database && this.props.database.allow_multi_schema_metadata_fetch) {
+      tableSelectPlaceholder = t('Type to search ...');
+    } else {
+      tableSelectPlaceholder = t('Select table ');
+      tableSelectDisabled = true;
+    }
     return (
       <div className="clearfix sql-toolbar">
         <div>
@@ -186,7 +195,6 @@ class SqlEditorLeftBar extends React.PureComponent {
               name="select-table"
               ref="selectTable"
               isLoading={this.state.tableLoading}
-              value={this.state.tableName}
               placeholder={t('Add a table (%s)', this.state.tableOptions.length)}
               autosize={false}
               onChange={this.changeTable.bind(this)}
@@ -199,8 +207,8 @@ class SqlEditorLeftBar extends React.PureComponent {
               async
               name="async-select-table"
               ref="selectTable"
-              value={this.state.tableName}
-              placeholder={t('Type to search ...')}
+              placeholder={tableSelectPlaceholder}
+              disabled={tableSelectDisabled}
               autosize={false}
               onChange={this.changeTable.bind(this)}
               loadOptions={this.getTableNamesBySubStr.bind(this)}