Add support for functions in where expressions

src/query_handler_test.go

@@ -499,6 +499,11 @@ func TestHandleQuery(t *testing.T) {
 			"description": {"type"},
 			"values":      {""},
 		},
+		// WHERE pg functions
+		"SELECT gss_authenticated, encrypted FROM (SELECT false, false, false, false, false WHERE false) t(pid, gss_authenticated, principal, encrypted, credentials_delegated) WHERE pid = pg_backend_pid()": {
+			"description": {"gss_authenticated", "encrypted"},
+			"values":      {},
+		},
 	}
 
 	for query, responses := range responsesByQuery {

src/select_remapper.go

@@ -86,6 +86,11 @@ func (selectRemapper *SelectRemapper) remapSelectStatement(selectStatement *pgQu
 		return selectStatement
 	}
 
+	// WHERE
+	if selectStatement.WhereClause != nil {
+		selectStatement = selectRemapper.remapWhereExpression(selectStatement, selectStatement.WhereClause, indentLevel)
+	}
+
 	// FROM
 	if len(selectStatement.FromClause) > 0 {
 		// SELECT
@@ -304,6 +309,29 @@ func (selectRemapper *SelectRemapper) remapTypeCastsInNode(node *pgQuery.Node) *
 	return node
 }
 
+func (selectRemapper *SelectRemapper) remapWhereExpression(selectStatement *pgQuery.SelectStmt, node *pgQuery.Node, indentLevel int) *pgQuery.SelectStmt {
+	selectRemapper.traceTreeTraversal("WHERE expression", indentLevel)
+
+	if aExpr := node.GetAExpr(); aExpr != nil {
+		if aExpr.Lexpr != nil {
+			selectRemapper.traceTreeTraversal("WHERE expression left", indentLevel+1)
+			selectStatement = selectRemapper.remapWhereExpression(selectStatement, aExpr.Lexpr, indentLevel+1)
+		}
+		if aExpr.Rexpr != nil {
+			selectRemapper.traceTreeTraversal("WHERE expression right", indentLevel+1)
+			selectStatement = selectRemapper.remapWhereExpression(selectStatement, aExpr.Rexpr, indentLevel+1)
+		}
+	}
+
+	if funcCall := node.GetFuncCall(); funcCall != nil {
+		if constantNode := selectRemapper.remapperSelect.remappedToConstant(funcCall); constantNode != nil {
+			node.Node = constantNode.Node
+		}
+	}
+
+	return selectStatement
+}
+
 func (selectRemapper *SelectRemapper) remapJoinExpressions(selectStatement *pgQuery.SelectStmt, node *pgQuery.Node, indentLevel int) *pgQuery.Node {
 	selectRemapper.traceTreeTraversal("JOIN left", indentLevel)
 	leftJoinNode := node.GetJoinExpr().Larg