expression: PropagateType should never let orignal data overflow (#…

…53045) close #52672
pingcap · May 9, 2024 · c33b6cd · c33b6cd
1 parent f304f04
commit c33b6cd
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Showing 3 changed files with 23 additions and 1 deletion.
diff --git a/pkg/expression/expression.go b/pkg/expression/expression.go
@@ -28,6 +28,7 @@ import (
 	"github.com/pingcap/tidb/pkg/types"
 	"github.com/pingcap/tidb/pkg/util/chunk"
 	"github.com/pingcap/tidb/pkg/util/generatedexpr"
+	"github.com/pingcap/tidb/pkg/util/mathutil"
 	"github.com/pingcap/tidb/pkg/util/size"
 	"github.com/pingcap/tidb/pkg/util/zeropool"
 )
@@ -1214,6 +1215,21 @@ func PropagateType(evalType types.EvalType, args ...Expression) {
 				if newDecimal > mysql.MaxDecimalScale {
 					newDecimal = mysql.MaxDecimalScale
 				}
+				if oldFlen-oldDecimal > newFlen-newDecimal {
+					// the input data should never be overflow under the new type
+					if newDecimal > oldDecimal {
+						// if the target decimal part is larger than the original decimal part, we try to extend
+						// the decimal part as much as possible while keeping the integer part big enough to hold
+						// the original data. For example, original type is Decimal(50, 0), new type is Decimal(48,30), then
+						// incDecimal = min(30-0, mysql.MaxDecimalWidth-50) = 15
+						// the new target Decimal will be Decimal(50+15, 0+15) = Decimal(65, 15)
+						incDecimal := mathutil.Min(newDecimal-oldDecimal, mysql.MaxDecimalWidth-oldFlen)
+						newFlen = oldFlen + incDecimal
+						newDecimal = oldDecimal + incDecimal
+					} else {
+						newFlen, newDecimal = oldFlen, oldDecimal
+					}
+				}
 			}
 			args[0].GetType().SetFlenUnderLimit(newFlen)
 			args[0].GetType().SetDecimalUnderLimit(newDecimal)

diff --git a/tests/integrationtest/r/executor/issues.result b/tests/integrationtest/r/executor/issues.result
@@ -865,3 +865,6 @@ SELECT  count(`t`.`c`) FROM (`s`) JOIN `t`  GROUP BY `t`.`c`;
 count(`t`.`c`)
 170
 set @@tidb_max_chunk_size = default;
+select tan(9021874879467600608071521900001091070693729763119983979);
+tan(9021874879467600608071521900001091070693729763119983979)
+8.068627196084492
diff --git a/tests/integrationtest/t/executor/issues.test b/tests/integrationtest/t/executor/issues.test
@@ -659,4 +659,7 @@ insert into s values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),
 insert into s values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1);
 SELECT /*+ stream_agg()*/ count(`t`.`c`) FROM (`s`) JOIN `t` GROUP BY `t`.`c`;
 SELECT  count(`t`.`c`) FROM (`s`) JOIN `t`  GROUP BY `t`.`c`;
-set @@tidb_max_chunk_size = default;
+set @@tidb_max_chunk_size = default;
+
+# TestIssue52672
+select tan(9021874879467600608071521900001091070693729763119983979);