// applyConstraints applies the constraints on values specified by constraints
// to an expression, simplifying the expression where possible. For example, if
// the expression is "a = 1" and the constraint is "a = 1", the expression can
// be simplified to "true". If the expression is "a = 1 AND b > 2" and the
// constraint is "a = 1", the expression is simplified to "b > 2".
//
// Note that applyConstraints currently only handles simple cases.
func applyConstraints(expr parser.Expr, constraints indexConstraints) parser.Expr {
v := &applyConstraintsVisitor{}
for _, c := range constraints {
v.constraint = c
expr = parser.WalkExpr(v, expr)
// We can only continue to apply the constraints if the constraints we have
// applied so far are equality constraints. There are two cases to
// consider: the first is that both the start and end constraints are
// equality.
if c.start == c.end {
if c.start.Operator == parser.EQ {
continue
}
// The second case is that both the start and end constraint are an IN
// operator with only a single value.
if c.start.Operator == parser.In && len(c.start.Right.(parser.DTuple)) == 1 {
continue
}
}
break
}
if expr == parser.DBool(true) {
return nil
}
return expr
}
// applyConstraints applies the constraints on values specified by constraints
// to an expression, simplifying the expression where possible. For example, if
// the expression is "a = 1" and the constraint is "a = 1", the expression can
// be simplified to "true". If the expression is "a = 1 AND b > 2" and the
// constraint is "a = 1", the expression is simplified to "b > 2".
//
// Note that applyConstraints currently only handles simple cases.
func applyConstraints(expr parser.Expr, constraints orIndexConstraints) parser.Expr {
if len(constraints) != 1 {
// We only support simplifying the expressions if there aren't multiple
// disjunctions (top-level OR branches).
return expr
}
v := &applyConstraintsVisitor{}
for _, c := range constraints[0] {
v.constraint = c
expr, _ = parser.WalkExpr(v, expr)
// We can only continue to apply the constraints if the constraints we have
// applied so far are equality constraints. There are two cases to
// consider: the first is that both the start and end constraints are
// equality.
if c.start == c.end {
if c.start.Operator == parser.EQ {
continue
}
// The second case is that both the start and end constraint are an IN
// operator with only a single value.
if c.start.Operator == parser.In && len(c.start.Right.(parser.DTuple)) == 1 {
continue
}
}
break
}
if expr == parser.DBool(true) {
return nil
}
return expr
}
// countVars counts how many *QualifiedName and *qvalue nodes are in an expression.
func countVars(expr parser.Expr) (numQNames, numQValues int) {
v := countVarsVisitor{}
if expr != nil {
parser.WalkExpr(&v, expr)
}
return v.numQNames, v.numQValues
}
func (p *planner) collectSubqueryPlans(expr parser.Expr, result []planNode) []planNode {
if expr == nil {
return result
}
p.collectSubqueryPlansVisitor = collectSubqueryPlansVisitor{plans: result}
_, _ = parser.WalkExpr(&p.collectSubqueryPlansVisitor, expr)
return p.collectSubqueryPlansVisitor.plans
}
func (p *planner) expandSubqueryPlans(expr parser.Expr) error {
if expr == nil {
return nil
}
p.subqueryPlanVisitor = subqueryPlanVisitor{doExpand: true}
_, _ = parser.WalkExpr(&p.subqueryPlanVisitor, expr)
return p.subqueryPlanVisitor.err
}
func (q *qvalue) Walk(v parser.Visitor) parser.Expr {
e, _ := parser.WalkExpr(v, q.datum)
// Typically Walk implementations are not supposed to modify nodes in-place, in order to
// preserve the original transaction statement and expressions. However, `qvalue` is our type
// (which we have "stiched" into an expression) so we aren't modifying an original expression.
q.datum = e.(parser.Datum)
return q
}
func (s *selectNode) resolveQNames(expr parser.Expr) (parser.Expr, *roachpb.Error) {
if expr == nil {
return expr, nil
}
v := qnameVisitor{selNode: s}
expr = parser.WalkExpr(&v, expr)
return expr, v.pErr
}
func (n *scanNode) resolveQNames(expr parser.Expr) (parser.Expr, error) {
if expr == nil {
return expr, nil
}
v := qnameVisitor{scanNode: n}
expr = parser.WalkExpr(&v, expr)
return expr, v.err
}
func (p *planner) aggregateInWhere(where *parser.Where) bool {
if where != nil {
defer p.isAggregateVisitor.reset()
_ = parser.WalkExpr(&p.isAggregateVisitor, where.Expr)
if p.isAggregateVisitor.aggregated {
return true
}
}
return false
}
func (p *planner) startSubqueryPlans(expr parser.Expr) error {
if expr == nil {
return nil
}
// We also run and pre-evaluate the subqueries during start,
// so as to avoid re-running the sub-query for every row
// in the results of the surrounding planNode.
p.subqueryPlanVisitor = subqueryPlanVisitor{doStart: true, doEval: true}
_, _ = parser.WalkExpr(&p.subqueryPlanVisitor, expr)
return p.subqueryPlanVisitor.err
}
// applyConstraints applies the constraints on values specified by constraints
// to an expression, simplifying the expression where possible. For example, if
// the expression is "a = 1" and the constraint is "a = 1", the expression can
// be simplified to "true". If the expression is "a = 1 AND b > 2" and the
// constraint is "a = 1", the expression is simplified to "b > 2".
//
// Note that applyConstraints currently only handles simple cases.
func applyConstraints(expr parser.Expr, constraints indexConstraints) parser.Expr {
v := &applyConstraintsVisitor{}
for _, c := range constraints {
v.constraint = c
expr = parser.WalkExpr(v, expr)
}
if expr == parser.DBool(true) {
return nil
}
return expr
}
func (p *planner) isAggregate(n *parser.Select) bool {
if n.Having != nil || len(n.GroupBy) > 0 {
return true
}
for _, target := range n.Exprs {
_ = parser.WalkExpr(&p.isAggregateVisitor, target.Expr)
if p.isAggregateVisitor.aggregated {
return true
}
}
return false
}
func resolveQNames(table *tableInfo, qvals qvalMap, expr parser.Expr) (parser.Expr, error) {
if expr == nil {
return expr, nil
}
v := qnameVisitor{
qt: qvalResolver{
table: table,
qvals: qvals,
},
}
expr = parser.WalkExpr(&v, expr)
return expr, v.err
}
func isAggregateExprs(n *parser.Select) bool {
if n.Having != nil || len(n.GroupBy) > 0 {
return true
}
v := isAggregateVisitor{}
for _, target := range n.Exprs {
_ = parser.WalkExpr(&v, target.Expr)
if v.aggregated {
return true
}
}
return false
}
// resolveQNames walks the provided expression and resolves all qualified
// names using the tableInfo and qvalMap. The function takes an optional
// qnameVisitor to provide the caller the option of avoiding an allocation.
func resolveQNames(expr parser.Expr, table *tableInfo, qvals qvalMap, v *qnameVisitor) (parser.Expr, error) {
if expr == nil {
return expr, nil
}
if v == nil {
v = new(qnameVisitor)
}
*v = qnameVisitor{
qt: qvalResolver{
table: table,
qvals: qvals,
},
}
expr, _ = parser.WalkExpr(v, expr)
return expr, v.err
}
// Check if exprs use aggregation and if they are valid.
// An expression is valid if:
// - it is an aggregate expression, or
// - it appears verbatim in groupBy, or
// - it is not a qvalue, and all of its subexpressions (as defined by
// its Walk implementation) are valid
// NB: "verbatim" above is defined using a string-equality comparison
// as an approximation of a recursive tree-equality comparison.
//
// For example:
// Invalid: `SELECT k, SUM(v) FROM kv`
// - `k` is unaggregated and does not appear in the (missing) GROUP BY.
// Valid: `SELECT k, SUM(v) FROM kv GROUP BY k`
// Also valid: `SELECT UPPER(k), SUM(v) FROM kv GROUP BY UPPER(k)`
// - `UPPER(k)` appears in GROUP BY.
// Also valid: `SELECT UPPER(k), SUM(v) FROM kv GROUP BY k`
// - `k` appears in GROUP BY, so `UPPER(k)` is OK, but...
// Invalid: `SELECT k, SUM(v) FROM kv GROUP BY UPPER(k)`
// - `k` does not appear in GROUP BY; UPPER(k) does nothing to help here.
func checkAggregateExprs(groupBy parser.GroupBy, exprs []parser.Expr) error {
v := checkAggregateVisitor{}
// TODO(dt): consider other ways of comparing expression trees.
v.groupStrs = make(map[string]struct{}, len(groupBy))
for i := range groupBy {
v.groupStrs[groupBy[i].String()] = struct{}{}
}
for _, expr := range exprs {
_ = parser.WalkExpr(&v, expr)
if v.aggrErr != nil {
return v.aggrErr
}
}
return nil
}
// resolveQNames walks the provided expression and resolves all qualified
// names using the tableInfo and qvalMap. The function takes an optional
// qnameVisitor to provide the caller the option of avoiding an allocation.
func resolveQNames(
expr parser.Expr, sources multiSourceInfo, qvals qvalMap, v *qnameVisitor,
) (parser.Expr, error) {
if expr == nil {
return expr, nil
}
if v == nil {
v = new(qnameVisitor)
}
*v = qnameVisitor{
qt: qvalResolver{
sources: sources,
qvals: qvals,
},
}
expr, _ = parser.WalkExpr(v, expr)
return expr, v.err
}
// processExpression parses the string expression inside an Expression,
// interpreting $0, $1, etc as indexed variables.
func processExpression(exprSpec Expression, h *parser.IndexedVarHelper) (parser.TypedExpr, error) {
expr, err := parser.ParseExprTraditional(exprSpec.Expr)
if err != nil {
return nil, err
}
// Convert ValArgs to IndexedVars
v := valArgsConvert{h: h, err: nil}
expr, _ = parser.WalkExpr(&v, expr)
if v.err != nil {
return nil, v.err
}
// Convert to a fully typed expression.
typedExpr, err := parser.TypeCheck(expr, nil, nil)
if err != nil {
return nil, err
}
return typedExpr, nil
}
func extractAggregateFuncs(expr parser.Expr) (parser.Expr, []*aggregateFunc, error) {
v := extractAggregatesVisitor{}
expr = parser.WalkExpr(&v, expr)
return expr, v.funcs, v.err
}
func (q *qvalue) Walk(v parser.Visitor) {
q.datum = parser.WalkExpr(v, q.datum).(parser.Datum)
}
func (p *planner) expandSubqueries(expr parser.Expr, columns int) (parser.Expr, *roachpb.Error) {
p.subqueryVisitor = subqueryVisitor{planner: p, columns: columns}
expr = parser.WalkExpr(&p.subqueryVisitor, expr)
return expr, p.subqueryVisitor.pErr
}
func (v *extractAggregatesVisitor) run(expr parser.Expr) (parser.Expr, []*aggregateFunc, error) {
*v = extractAggregatesVisitor{}
expr = parser.WalkExpr(v, expr)
return expr, v.funcs, v.err
}
// Convert the variables in the given expression; the expression must only contain
// variables known to the conversion function (exprCheckVars should be used first).
func exprConvertVars(expr parser.TypedExpr, conv varConvertFunc) parser.TypedExpr {
v := varConvertVisitor{justCheck: false, conv: conv}
ret, _ := parser.WalkExpr(&v, expr)
return ret.(parser.TypedExpr)
}
func (p *planner) expandSubqueries(expr parser.Expr, columns int) (parser.Expr, error) {
p.subqueryVisitor = subqueryVisitor{planner: p, columns: columns}
p.subqueryVisitor.path = p.subqueryVisitor.pathBuf[:0]
expr, _ = parser.WalkExpr(&p.subqueryVisitor, expr)
return expr, p.subqueryVisitor.err
}
func (v *extractAggregatesVisitor) run(n *groupNode, expr parser.Expr) (parser.Expr, error) {
*v = extractAggregatesVisitor{n: n}
expr = parser.WalkExpr(v, expr)
return expr, v.err
}
// Walk implements the Expr interface.
func (q *qvalue) Walk(v parser.Visitor) parser.Expr {
if e, changed := parser.WalkExpr(v, q.datum); changed {
return &qvalue{datum: e.(parser.Datum), colRef: q.colRef}
}
return q
}
// isConst returns true if the expression contains only constant values
// (i.e. it does not contain a DReference).
func isConst(expr parser.Expr) bool {
v := isConstVisitor{isConst: true}
expr = parser.WalkExpr(&v, expr)
return v.isConst
}
// Extract aggregateFuncs from exprs that use aggregation and check if they are valid.
// An expression is valid if:
// - it is an aggregate expression, or
// - it appears verbatim in groupBy, or
// - it is not a qvalue, and all of its subexpressions (as defined by
// its Walk implementation) are valid
// NB: "verbatim" above is defined using a string-equality comparison
// as an approximation of a recursive tree-equality comparison.
//
// For example:
// Invalid: `SELECT k, SUM(v) FROM kv`
// - `k` is unaggregated and does not appear in the (missing) GROUP BY.
// Valid: `SELECT k, SUM(v) FROM kv GROUP BY k`
// Also valid: `SELECT UPPER(k), SUM(v) FROM kv GROUP BY UPPER(k)`
// - `UPPER(k)` appears in GROUP BY.
// Also valid: `SELECT UPPER(k), SUM(v) FROM kv GROUP BY k`
// - `k` appears in GROUP BY, so `UPPER(k)` is OK, but...
// Invalid: `SELECT k, SUM(v) FROM kv GROUP BY UPPER(k)`
// - `k` does not appear in GROUP BY; UPPER(k) does nothing to help here.
func (v extractAggregatesVisitor) extract(expr parser.Expr) (parser.Expr, error) {
expr = parser.WalkExpr(&v, expr)
return expr, v.err
}
func (v *extractAggregatesVisitor) Visit(expr parser.Expr, pre bool) (parser.Visitor, parser.Expr) {
if !pre || v.err != nil {
return nil, expr
}
// This expression is in the GROUP BY - switch to the copy that will accept
// qvalues for this and any subtrees.
if _, ok := v.groupStrs[expr.String()]; ok && v.groupedCopy != nil {
v = v.groupedCopy
}
switch t := expr.(type) {
case *parser.FuncExpr:
if len(t.Name.Indirect) > 0 {
break
}
if impl, ok := aggregates[strings.ToLower(string(t.Name.Base))]; ok {
if len(t.Exprs) != 1 {
// Type checking has already run on these expressions thus
// if an aggregate function of the wrong arity gets here,
// something has gone really wrong.
panic(fmt.Sprintf("%s has %d arguments (expected 1)", t.Name.Base, len(t.Exprs)))
}
defer v.subAggregateVisitor.reset()
_ = parser.WalkExpr(&v.subAggregateVisitor, t.Exprs[0])
if v.subAggregateVisitor.aggregated {
v.err = fmt.Errorf("aggregate function calls cannot be nested under %s", t.Name)
return v, expr
}
f := &aggregateFunc{
expr: t,
arg: t.Exprs[0],
create: impl,
group: v.n,
buckets: make(map[string]aggregateImpl),
}
if t.Type == parser.Distinct {
f.seen = make(map[string]struct{})
}
v.n.funcs = append(v.n.funcs, f)
return nil, f
}
case *qvalue:
if v.groupedCopy != nil {
v.err = fmt.Errorf("column \"%s\" must appear in the GROUP BY clause or be used in an aggregate function",
t.colRef.get().Name)
return v, expr
}
f := &aggregateFunc{
expr: t,
arg: t,
create: newIdentAggregate,
group: v.n,
buckets: make(map[string]aggregateImpl),
}
v.n.funcs = append(v.n.funcs, f)
return nil, f
}
return v, expr
}
func checkAggregateExpr(expr parser.Expr) error {
v := checkAggregateVisitor{}
_ = parser.WalkExpr(&v, expr)
return v.err
}
