View Presto row and array objects clearly in the data grid (#7625)

* feat: rough check in for Presto rows and arrays

* fix: presto arrays

* fix: return selected and expanded columns

* fix: add helper methods and unit tests

* fix: only allow exploration of selected columns

* fix: address Beto's comments and add more unit tests

superset/assets/spec/javascripts/sqllab/fixtures.js

@@ -223,6 +223,20 @@ export const queries = [
           type: 'STRING',
         },
       ],
+      selected_columns: [
+        {
+          is_date: true,
+          is_dim: false,
+          name: 'ds',
+          type: 'STRING',
+        },
+        {
+          is_date: false,
+          is_dim: true,
+          name: 'gender',
+          type: 'STRING',
+        },
+      ],
       data: [{ col1: 0, col2: 1 }, { col1: 2, col2: 3 }],
     },
   },
@@ -264,7 +278,7 @@ export const queryWithBadColumns = {
   ...queries[0],
   results: {
     data: queries[0].results.data,
-    columns: [
+    selected_columns: [
       {
         is_date: true,
         is_dim: false,

superset/assets/src/SqlLab/components/ExploreResultsButton.jsx

@@ -85,8 +85,8 @@ class ExploreResultsButton extends React.PureComponent {
   }
   getColumns() {
     const props = this.props;
-    if (props.query && props.query.results && props.query.results.columns) {
-      return props.query.results.columns;
+    if (props.query && props.query.results && props.query.results.selected_columns) {
+      return props.query.results.selected_columns;
     }
     return [];
   }
@@ -97,7 +97,7 @@ class ExploreResultsButton extends React.PureComponent {
     const re1 = /^[A-Za-z_]\w*$/;  // starts with char or _, then only alphanum
     const re2 = /__\d+$/;  // does not finish with __ and then a number which screams dup col name
 
-    return this.props.query.results.columns.map(col => col.name)
+    return this.props.query.results.selected_columns.map(col => col.name)
       .filter(col => !re1.test(col) || re2.test(col));
   }
   datasourceName() {

superset/assets/src/SqlLab/main.less

@@ -238,6 +238,7 @@ div.Workspace {
 
     .schemaPane {
         flex: 0 0 300px;
+        max-width: 300px;
         transition: all .3s ease-in-out;
     }