feat(compiler): Support subqueries in the FROM clause

issue #2989, #2400 and probably others

internal/compiler/query_catalog.go

@@ -9,26 +9,36 @@ import (
 )
 
 type QueryCatalog struct {
-catalog *catalog.Catalog
-ctes map[string]*Table
-embeds rewrite.EmbedSet
+catalog *catalog.Catalog
+ctes map[string]*Table
+fromClauses map[string]*Table
+embeds rewrite.EmbedSet
 }
 
 func (comp *Compiler) buildQueryCatalog(c *catalog.Catalog, node ast.Node, embeds rewrite.EmbedSet) (*QueryCatalog, error) {
 var with *ast.WithClause
+var from *ast.List
 switch n := node.(type) {
 case *ast.DeleteStmt:
 with = n.WithClause
 case *ast.InsertStmt:
 with = n.WithClause
 case *ast.UpdateStmt:
 with = n.WithClause
+from = n.FromClause
 case *ast.SelectStmt:
 with = n.WithClause
+from = n.FromClause
 default:
 with = nil
+from = nil
+}
+qc := &QueryCatalog{
+catalog: c,
+ctes: map[string]*Table{},
+fromClauses: map[string]*Table{},
+embeds: embeds,
 }
-qc := &QueryCatalog{catalog: c, ctes: map[string]*Table{}, embeds: embeds}
 if with != nil {
 for _, item := range with.Ctes.Items {
 if cte, ok := item.(*ast.CommonTableExpr); ok {
@@ -60,6 +70,37 @@ func (comp *Compiler) buildQueryCatalog(c *catalog.Catalog, node ast.Node, embed
 }
 }
 }
+if from != nil {
+for _, item := range from.Items {
+if rs, ok := item.(*ast.RangeSubselect); ok {
+cols, err := comp.outputColumns(qc, rs.Subquery)
+if err != nil {
+return nil, err
+}
+var names []string
+if rs.Alias.Colnames != nil {
+for _, item := range rs.Alias.Colnames.Items {
+if val, ok := item.(*ast.String); ok {
+names = append(names, val.Str)
+} else {
+names = append(names, "")
+}
+}
+}
+rel := &ast.TableName{Name: *rs.Alias.Aliasname}
+for i := range cols {
+cols[i].Table = rel
+if len(names) > i {
+cols[i].Name = names[i]
+}
+}
+qc.fromClauses[*rs.Alias.Aliasname] = &Table{
+Rel: rel,
+Columns: cols,
+}
+}
+}
+}
 return qc, nil
 }
 

internal/compiler/resolve.go

@@ -111,6 +111,28 @@ func (comp *Compiler) resolveCatalogRefs(qc *QueryCatalog, rvs []*ast.RangeVar,
 aliasMap[*rv.Alias.Aliasname] = fqn
 }
 }
+for _, f := range qc.fromClauses {
+catCols := make([]*catalog.Column, 0, len(f.Columns))
+for _, col := range f.Columns {
+catCols = append(catCols, &catalog.Column{
+Name: col.Name,
+Type: ast.TypeName{Name: col.DataType},
+IsNotNull: col.NotNull,
+IsUnsigned: col.Unsigned,
+IsArray: col.IsArray,
+ArrayDims: col.ArrayDims,
+Comment: col.Comment,
+Length: col.Length,
+})
+}
+
+if err := indexTable(catalog.Table{
+Rel: f.Rel,
+Columns: catCols,
+}); err != nil {
+return nil, err
+}
+}
 
 // resolve a table for an embed
 for _, embed := range embeds {

internal/endtoend/testdata/join_alias/mysql/query.sql

@@ -9,3 +9,9 @@ SELECT *
 FROM foo f
 JOIN bar b ON b.id = f.id
 WHERE f.id = ?;
+
+-- name: SubqueryAlias :many
+SELECT * FROM (SELECT 1 AS n) AS x WHERE x.n <= ?;
+
+-- name: ColumnAlias :many
+SELECT * FROM (SELECT 1 AS n) AS x WHERE n <= ?;