plan: refine return type, charset and collation for 'get variable' ex…

…pression (pingcap#4550)
pazhang · Sep 19, 2017 · 8794374 · 8794374
1 parent 9e6accb
commit 8794374
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Showing 3 changed files with 9 additions and 8 deletions.
diff --git a/plan/expression_rewriter.go b/plan/expression_rewriter.go
@@ -25,6 +25,7 @@ import (
 	"github.com/pingcap/tidb/model"
 	"github.com/pingcap/tidb/mysql"
 	"github.com/pingcap/tidb/parser/opcode"
+	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/sessionctx/varsutil"
 	"github.com/pingcap/tidb/util/charset"
 	"github.com/pingcap/tidb/util/types"
@@ -764,7 +765,10 @@ func (er *expressionRewriter) rewriteVariable(v *ast.VariableExpr) {
 		er.err = errors.Trace(err)
 		return
 	}
-	er.ctxStack = append(er.ctxStack, datumToConstant(types.NewStringDatum(val), mysql.TypeString))
+	e := datumToConstant(types.NewStringDatum(val), mysql.TypeVarString)
+	e.RetType.Charset = er.ctx.GetSessionVars().Systems[variable.CharacterSetConnection]
+	e.RetType.Collate = er.ctx.GetSessionVars().Systems[variable.CollationConnection]
+	er.ctxStack = append(er.ctxStack, e)
 	return
 }
 

diff --git a/sessionctx/variable/session.go b/sessionctx/variable/session.go
@@ -248,11 +248,6 @@ func NewSessionVars() *SessionVars {
 	}
 }
 
-const (
-	characterSetConnection = "character_set_connection"
-	collationConnection    = "collation_connection"
-)
-
 // GetCharsetInfo gets charset and collation for current context.
 // What character set should the server translate a statement to after receiving it?
 // For this, the server uses the character_set_connection and collation_connection system variables.
@@ -263,8 +258,8 @@ const (
 // have their own collation, which has a higher collation precedence.
 // See https://dev.mysql.com/doc/refman/5.7/en/charset-connection.html
 func (s *SessionVars) GetCharsetInfo() (charset, collation string) {
-	charset = s.Systems[characterSetConnection]
-	collation = s.Systems[collationConnection]
+	charset = s.Systems[CharacterSetConnection]
+	collation = s.Systems[CollationConnection]
 	return
 }
 

diff --git a/sessionctx/variable/sysvar.go b/sessionctx/variable/sysvar.go
@@ -628,6 +628,8 @@ var SetNamesVariables = []string{
 }
 
 const (
+	// CharacterSetConnection is the name for character_set_connection system variable.
+	CharacterSetConnection = "character_set_connection"
 	// CollationConnection is the name for collation_connection system variable.
 	CollationConnection = "collation_connection"
 	// CharsetDatabase is the name for character_set_database system variable.