Expressions: Sql expressions with Duckdb (#81666)

duckdb temp storage of dataframes using parquet and querying from sql expressions
---------

Co-authored-by: Ryan McKinley <ryantxu@gmail.com>

pkg/expr/models.go

@@ -24,6 +24,9 @@ const (
 
 	// Threshold
 	QueryTypeThreshold QueryType = "threshold"
+
+	// SQL query via DuckDB
+	QueryTypeSQL QueryType = "sql"
 )
 
 type MathQuery struct {
@@ -69,6 +72,11 @@ type ClassicQuery struct {
 	Conditions []classic.ConditionJSON `json:"conditions"`
 }
 
+// SQLQuery requires the sqlExpression feature flag
+type SQLExpression struct {
+	Expression string `json:"expression" jsonschema:"minLength=1,example=SELECT * FROM A LIMIT 1"`
+}
+
 //-------------------------------
 // Non-query commands
 //-------------------------------