Letting StackQL Project Functions Over Subqueries: Fixing JSON_EXTRACT Rewrites

A rewriter that tried to resolve every projection as a column, even when it was a function.

Kurze Antwort

Selecting an expression such as JSON_EXTRACT(contact_method, '$.html_url') from a subquery failed in StackQL with "query rewriting for indirection: cannot find col". The rewriter only let through projections that looked like json_each values or OR expressions; everything else had to match a subquery column by name. The fix treats any projection that isn't a bare column reference as an expression and passes it to the SQL backend. Bare column names that don't exist still error as before. It was merged as PR #722 and closed issue #352.

The problem

StackQL lets you query cloud and SaaS resources with SQL. Issue #352, opened in December 2023, showed a PagerDuty query that unpacked contact methods with json_each in a subquery and then used JSON_EXTRACT in the outer select. The rewriter couldn't find a column with the expression's inferred name and aborted.

The fix

-func (v *standardQueryRewriteAstVisitor) isAnonymous(col parserutil.ColumnHandle) bool {
-   switch col.Expr.(type) {
-   case *sqlparser.OrExpr:
-       return true
-   default:
-       return false
-   }
+func (v *standardQueryRewriteAstVisitor) isExpressionProjection(node *sqlparser.AliasedExpr) bool {
+   _, isColumnReference := node.Expr.(*sqlparser.ColName)
+   return !isColumnReference

Two Robot Framework scenarios cover it: a json_extract over a subquery (on the SQLite backend), and a coalesce with a literal leading argument (on both backends).

By the numbers

• Repository: stackql/stackql, 1,074 stars (Nov 3, 2026), Go, MIT
• Files changed: 2
• Lines: +39 / -9
• Commits: 1
• Opened: Aug 21, 2026. Merged: Aug 22, 2026. Time to merge: 16 hours
• Review: approved and merged by a maintainer

How the review went

A maintainer approved and merged it with "thank you for your contribution".

FAQ

Where can I read more?

See the pull request and the original issue.

Das Ziel

A rewriter should only resolve what it needs to. Treating expressions as opaque lets the database do the work it already knows how to do.