*: basic support show warnings. (pingcap#2724)

executor/show.go

@@ -30,6 +30,7 @@ import (
 	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/sessionctx/varsutil"
 	"github.com/pingcap/tidb/table"
+	"github.com/pingcap/tidb/terror"
 	"github.com/pingcap/tidb/util/charset"
 	"github.com/pingcap/tidb/util/types"
 )
@@ -109,7 +110,9 @@ func (e *ShowExec) fetchAll() error {
 		return e.fetchShowTriggers()
 	case ast.ShowVariables:
 		return e.fetchShowVariables()
-	case ast.ShowWarnings, ast.ShowProcessList, ast.ShowEvents:
+	case ast.ShowWarnings:
+		return e.fetchShowWarnings()
+	case ast.ShowProcessList, ast.ShowEvents:
 		// empty result
 	}
 	return nil
@@ -539,6 +542,25 @@ func (e *ShowExec) fetchShowProcedureStatus() error {
 	return nil
 }
 
+func (e *ShowExec) fetchShowWarnings() error {
+	warns := e.ctx.GetSessionVars().StmtCtx.GetWarnings()
+	for _, warn := range warns {
+		datums := make([]types.Datum, 3)
+		datums[0] = types.NewStringDatum("Warning")
+		switch x := warn.(type) {
+		case *terror.Error:
+			sqlErr := x.ToSQLError()
+			datums[1] = types.NewIntDatum(int64(sqlErr.Code))
+			datums[2] = types.NewStringDatum(sqlErr.Message)
+		default:
+			datums[1] = types.NewIntDatum(int64(mysql.ErrUnknown))
+			datums[2] = types.NewStringDatum(warn.Error())
+		}
+		e.rows = append(e.rows, &Row{Data: datums})
+	}
+	return nil
+}
+
 func (e *ShowExec) getTable() (table.Table, error) {
 	if e.Table == nil {
 		return nil, errors.New("table not found")

executor/show_test.go

@@ -20,6 +20,7 @@ import (
 	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/util/testkit"
 	"github.com/pingcap/tidb/util/testleak"
+	"github.com/pingcap/tidb/util/testutil"
 )
 
 func (s *testSuite) TestShow(c *C) {
@@ -215,5 +216,18 @@ func (s *testSuite) TestForeignKeyInShowCreateTable(c *C) {
 	for i, r := range row {
 		c.Check(r, Equals, expectedRow[i])
 	}
+}
 
+func (s *testSuite) TestShowWarnings(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	testSQL := `create table if not exists show_warnings (a int)`
+	tk.MustExec(testSQL)
+	tk.MustExec("set @@sql_mode=''")
+	tk.MustExec("insert show_warnings values ('a')")
+	c.Assert(tk.Se.GetSessionVars().StmtCtx.WarningCount(), Equals, uint16(1))
+	tk.MustQuery("show warnings").Check(testutil.RowsWithSep("|", "Warning|1265|Data Truncated"))
+	c.Assert(tk.Se.GetSessionVars().StmtCtx.WarningCount(), Equals, uint16(0))
+	tk.MustQuery("show warnings").Check(testutil.RowsWithSep("|", "Warning|1265|Data Truncated"))
+	c.Assert(tk.Se.GetSessionVars().StmtCtx.WarningCount(), Equals, uint16(0))
 }

plan/planbuilder.go

@@ -480,6 +480,8 @@ func (b *planBuilder) buildShow(show *ast.ShowStmt) Plan {
 		p.SetSchema(buildShowTriggerSchema())
 	case ast.ShowEvents:
 		p.SetSchema(buildShowEventsSchema())
+	case ast.ShowWarnings:
+		p.SetSchema(buildShowWarningsSchema())
 	default:
 		p.SetSchema(buildShowSchema(show))
 	}
@@ -831,6 +833,15 @@ func buildShowEventsSchema() *expression.Schema {
 	return schema
 }
 
+func buildShowWarningsSchema() *expression.Schema {
+	tblName := "WARNINGS"
+	schema := expression.NewSchema(make([]*expression.Column, 0, 3)...)
+	schema.Append(buildColumn(tblName, "Level", mysql.TypeVarchar, 64))
+	schema.Append(buildColumn(tblName, "Code", mysql.TypeLong, 19))
+	schema.Append(buildColumn(tblName, "Message", mysql.TypeVarchar, 64))
+	return schema
+}
+
 func composeShowSchema(names []string, ftypes []byte) *expression.Schema {
 	schema := expression.NewSchema(make([]*expression.Column, 0, len(names))...)
 	for i, name := range names {

server/driver_tidb.go

@@ -39,10 +39,9 @@ func NewTiDBDriver(store kv.Storage) *TiDBDriver {
 
 // TiDBContext implements QueryCtx.
 type TiDBContext struct {
-	session      tidb.Session
-	currentDB    string
-	warningCount uint16
-	stmts        map[int]*TiDBStatement
+	session   tidb.Session
+	currentDB string
+	stmts     map[int]*TiDBStatement
 }
 
 // TiDBStatement implements PreparedStatement.
@@ -185,7 +184,7 @@ func (tc *TiDBContext) CurrentDB() string {
 
 // WarningCount implements QueryCtx WarningCount method.
 func (tc *TiDBContext) WarningCount() uint16 {
-	return tc.warningCount
+	return tc.session.GetSessionVars().StmtCtx.WarningCount()
 }
 
 // Execute implements QueryCtx Execute method.

sessionctx/variable/session.go

@@ -14,6 +14,7 @@
 package variable
 
 import (
+	"math"
 	"strings"
 	"sync"
 	"time"
@@ -261,6 +262,7 @@ type StatementContext struct {
 	InUpdateOrDeleteStmt bool
 	IgnoreTruncate       bool
 	TruncateAsWarning    bool
+	InShowWarning        bool
 
 	/* Variables that changes during execution. */
 	mu struct {
@@ -310,6 +312,17 @@ func (sc *StatementContext) GetWarnings() []error {
 	return warns
 }
 
+// WarningCount gets warning count.
+func (sc *StatementContext) WarningCount() uint16 {
+	if sc.InShowWarning {
+		return 0
+	}
+	sc.mu.Lock()
+	wc := uint16(len(sc.mu.warnings))
+	sc.mu.Unlock()
+	return wc
+}
+
 // SetWarnings sets warnings.
 func (sc *StatementContext) SetWarnings(warns []error) {
 	sc.mu.Lock()
@@ -320,6 +333,8 @@ func (sc *StatementContext) SetWarnings(warns []error) {
 // AppendWarning appends a warning.
 func (sc *StatementContext) AppendWarning(warn error) {
 	sc.mu.Lock()
-	sc.mu.warnings = append(sc.mu.warnings, warn)
+	if len(sc.mu.warnings) < math.MaxUint16 {
+		sc.mu.warnings = append(sc.mu.warnings, warn)
+	}
 	sc.mu.Unlock()
 }

tidb.go

@@ -150,6 +150,7 @@ func resetStmtCtx(ctx context.Context, s ast.StmtNode) {
 		sc.IgnoreTruncate = true
 		if show, ok := s.(*ast.ShowStmt); ok {
 			if show.Tp == ast.ShowWarnings {
+				sc.InShowWarning = true
 				sc.SetWarnings(sessVars.StmtCtx.GetWarnings())
 			}
 		}