vitessio/vitess · error

unsupported select from dual

Error message

unsupported select from dual

What it means

analyzeSelectFrom requires the select's FROM clause to reference an actual table. A select with no FROM (i.e. 'select 1 from dual' / 'select expr') has no source table for a replication plan and is rejected with this error.

Source

Thrown at go/vt/vttablet/tabletmanager/vreplication/table_plan_builder.go:402

		CollationEnv:            tpb.collationEnv,
		WorkflowConfig:          tpb.workflowConfig,
	}
}

func analyzeSelectFrom(query string, parser *sqlparser.Parser) (sel *sqlparser.Select, from string, err error) {
	statement, err := parser.Parse(query)
	if err != nil {
		return nil, "", err
	}
	sel, ok := statement.(*sqlparser.Select)
	if !ok {
		return nil, "", errors.New("unsupported non-select statement")
	}
	if sel.Distinct {
		return nil, "", errors.New("unsupported distinct clause")
	}
	if len(sel.From) == 0 {
		return nil, "", errors.New("unsupported select from dual")
	}
	if len(sel.From) > 1 {
		return nil, "", errors.New("unsupported multi-table usage")
	}
	node, ok := sel.From[0].(*sqlparser.AliasedTableExpr)
	if !ok {
		return nil, "", fmt.Errorf("unsupported from expression (%T)", sel.From[0])
	}
	fromTable := sqlparser.GetTableName(node.Expr)
	if fromTable.IsEmpty() {
		return nil, "", fmt.Errorf("unsupported from source (%T)", node.Expr)
	}
	return sel, fromTable.String(), nil
}

func (tpb *tablePlanBuilder) analyzeExprs(selExprs []sqlparser.SelectExpr) error {
	for _, selExpr := range selExprs {
		cexpr, err := tpb.analyzeExpr(selExpr)

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Include a real table in the filter rule: 'select * from <table> where ...'
2. Fix rule generation so the table name is always interpolated into the filter query
3. Validate filter rules before submitting them to MoveTables/Reshard

Example fix

// before
"filter": "select 1"
// after
"filter": "select * from t where ..."

sel := stmt.(*sqlparser.Select)
if len(sel.From) == 0 || sel.From[0].SQLNode() == nil {
    return errors.New("filter rule must select from a table")
}

When it happens

Trigger: A filter rule whose query is 'select 1', 'select now()' or any FROM-less select (sqlparser yields an empty sel.From).

Common situations: Placeholder/test queries pasted into filter rules; generated rules where the table name was accidentally dropped.

Related errors

• unsupported mix of '*' and columns
• unsupported qualifier for '*' expression
• unsupported non-select statement
• unsupported distinct clause
• unexpected event on table %s

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/ccccebf3080cda2b. Report an issue: GitHub.