sql: implement VALIDATE of CHECK constraints

sql/alter_table.go

@@ -17,6 +17,7 @@
 package sql
 
 import (
+	"bytes"
 	"fmt"
 
 	"github.com/cockroachdb/cockroach/sql/parser"
@@ -248,16 +249,35 @@ func (n *alterTableNode) Start() error {
 				return err
 			}
 			name := string(t.Constraint)
-			details, ok := info[name]
+			constraint, ok := info[name]
 			if !ok {
 				return errors.Errorf("constraint %q does not exist", t.Constraint)
 			}
-			if !details.Unvalidated {
+			if !constraint.Unvalidated {
 				continue
 			}
-			switch details.Kind {
+			switch constraint.Kind {
+			case sqlbase.ConstraintTypeCheck:
+				found := false
+				var idx int
+				for idx = range n.tableDesc.Checks {
+					if n.tableDesc.Checks[idx].Name == name {
+						found = true
+						break
+					}
+				}
+				if !found {
+					panic("constrint returned by GetConstraintInfo not found")
+				}
+				ck := n.tableDesc.Checks[idx]
+				if err := n.p.validateCheckExpr(ck.Expr, &n.n.Table, n.tableDesc); err != nil {
+					return err
+				}
+				n.tableDesc.Checks[idx].Validity = sqlbase.ConstraintValidity_Validated
+				descriptorChanged = true
+
 			default:
-				return errors.Errorf("validating %s constraint %q unsupported", details.Kind, t.Constraint)
+				return errors.Errorf("validating %s constraint %q unsupported", constraint.Kind, t.Constraint)
 			}
 
 		case parser.ColumnMutationCmd:
@@ -371,3 +391,16 @@ func applyColumnMutation(col *sqlbase.ColumnDescriptor, mut parser.ColumnMutatio
 	}
 	return nil
 }
+
+func labeledRowValues(cols []sqlbase.ColumnDescriptor, values parser.DTuple) string {
+	var s bytes.Buffer
+	for i := range cols {
+		if i != 0 {
+			s.WriteString(`, `)
+		}
+		s.WriteString(cols[i].Name)
+		s.WriteString(`=`)
+		s.WriteString(values[i].String())
+	}
+	return s.String()
+}

sql/check.go

@@ -19,6 +19,7 @@ import (
 
 	"github.com/cockroachdb/cockroach/sql/parser"
 	"github.com/cockroachdb/cockroach/sql/sqlbase"
+	"github.com/pkg/errors"
 )
 
 type checkHelper struct {
@@ -89,3 +90,40 @@ func (c *checkHelper) check(ctx *parser.EvalContext) error {
 	}
 	return nil
 }
+
+func (p *planner) validateCheckExpr(
+	exprStr string,
+	tableName parser.TableExpr,
+	tableDesc *sqlbase.TableDescriptor,
+) error {
+	expr, err := parser.ParseExprTraditional(exprStr)
+	if err != nil {
+		return err
+	}
+	sel := &parser.SelectClause{
+		Exprs: sqlbase.ColumnsSelectors(tableDesc.Columns),
+		From:  &parser.From{Tables: parser.TableExprs{tableName}},
+		Where: &parser.Where{Expr: &parser.NotExpr{Expr: expr}},
+	}
+	lim := &parser.Limit{Count: parser.NewDInt(1)}
+	// This could potentially use a variant of planner.SelectClause that could
+	// use the tableDesc we have, but this is a rare operation and be benefit
+	// would be marginal compared to the work of the actual query, so the added
+	// complexity seems unjustified.
+	rows, err := p.SelectClause(sel, nil, lim, nil, publicColumns)
+	if err := rows.expandPlan(); err != nil {
+		return err
+	}
+	if err := rows.Start(); err != nil {
+		return err
+	}
+	next, err := rows.Next()
+	if err != nil {
+		return err
+	}
+	if next {
+		return errors.Errorf("validation of CHECK %q failed on row: %s",
+			expr.String(), labeledRowValues(tableDesc.Columns, rows.Values()))
+	}
+	return nil
+}

sql/parser/sql.y

@@ -913,7 +913,7 @@ opt_validate_behavior:
   }
 | /* EMPTY */
   {
-  $$.val = ValidationDefault
+    $$.val = ValidationDefault
   }
 
 opt_collate_clause:

sql/testdata/alter_table

@@ -124,12 +124,27 @@ t  fk_f_ref_other  FOREIGN KEY          f  other.[b]
 t  foo             UNIQUE               b  NULL
 t  primary         PRIMARY KEY          a  NULL
 
-statement error validating CHECK constraint "check_a" unsupported
+statement error constraint "typo" does not exist
+ALTER TABLE t VALIDATE CONSTRAINT typo
+
+statement error validation of CHECK "a > 0" failed on row: a=-2, f=9, b=NULL, c=NULL
 ALTER TABLE t VALIDATE CONSTRAINT check_a
 
 statement ok
 DELETE FROM t WHERE a = -2
 
+statement ok
+ALTER TABLE t VALIDATE CONSTRAINT check_a
+
+query TTTTT
+SHOW CONSTRAINTS FROM t
+----
+t  check_a         CHECK                NULL  a > 0
+t  check_a1        CHECK (UNVALIDATED)  NULL  a > 0
+t  fk_f_ref_other  FOREIGN KEY          f  other.[b]
+t  foo             UNIQUE               b  NULL
+t  primary         PRIMARY KEY          a  NULL
+
 statement ok
 ALTER TABLE t DROP CONSTRAINT check_a, DROP CONSTRAINT check_a1