expression: support JSON for builtin function COALESCE (#9087) (#9198)

pingcap · Jan 28, 2019 · 721193c · 721193c
1 parent fda9e84
commit 721193c
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Showing 2 changed files with 29 additions and 0 deletions.
diff --git a/expression/builtin_compare.go b/expression/builtin_compare.go
@@ -203,6 +203,9 @@ func (c *coalesceFunctionClass) getFunction(ctx sessionctx.Context, args []Expre
 		}
 		sig = &builtinCoalesceDurationSig{bf}
 		sig.setPbCode(tipb.ScalarFuncSig_CoalesceDuration)
+	case types.ETJson:
+		sig = &builtinCoalesceJSONSig{bf}
+		sig.setPbCode(tipb.ScalarFuncSig_CoalesceJson)
 	}
 
 	return sig, nil
@@ -340,6 +343,28 @@ func (b *builtinCoalesceDurationSig) evalDuration(row chunk.Row) (res types.Dura
 	return res, isNull, errors.Trace(err)
 }
 
+// builtinCoalesceJSONSig is buitin function coalesce signature which return type json.
+// See http://dev.mysql.com/doc/refman/5.7/en/comparison-operators.html#function_coalesce
+type builtinCoalesceJSONSig struct {
+	baseBuiltinFunc
+}
+
+func (b *builtinCoalesceJSONSig) Clone() builtinFunc {
+	newSig := &builtinCoalesceJSONSig{}
+	newSig.cloneFrom(&b.baseBuiltinFunc)
+	return newSig
+}
+
+func (b *builtinCoalesceJSONSig) evalJSON(row chunk.Row) (res json.BinaryJSON, isNull bool, err error) {
+	for _, a := range b.getArgs() {
+		res, isNull, err = a.EvalJSON(b.ctx, row)
+		if err != nil || !isNull {
+			break
+		}
+	}
+	return res, isNull, err
+}
+
 // temporalWithDateAsNumEvalType makes DATE, DATETIME, TIMESTAMP pretend to be numbers rather than strings.
 func temporalWithDateAsNumEvalType(argTp *types.FieldType) (argEvalType types.EvalType, isStr bool, isTemporalWithDate bool) {
 	argEvalType = argTp.EvalType()

diff --git a/expression/integration_test.go b/expression/integration_test.go
@@ -2790,6 +2790,10 @@ func (s *testIntegrationSuite) TestCompareBuiltin(c *C) {
 	// for coalesce
 	result = tk.MustQuery("select coalesce(NULL), coalesce(NULL, NULL), coalesce(NULL, NULL, NULL);")
 	result.Check(testkit.Rows("<nil> <nil> <nil>"))
+	tk.MustQuery(`select coalesce(cast(1 as json), cast(2 as json));`).Check(testkit.Rows(`1`))
+	tk.MustQuery(`select coalesce(NULL, cast(2 as json));`).Check(testkit.Rows(`2`))
+	tk.MustQuery(`select coalesce(cast(1 as json), NULL);`).Check(testkit.Rows(`1`))
+	tk.MustQuery(`select coalesce(NULL, NULL);`).Check(testkit.Rows(`<nil>`))
 
 	tk.MustExec("drop table if exists t2")
 	tk.MustExec("create table t2(a int, b double, c datetime, d time, e char(20), f bit(10))")