luoyuxia commented on code in PR #18975:
URL: https://github.com/apache/flink/pull/18975#discussion_r959114755
##########
flink-connectors/flink-connector-hive/src/test/java/org/apache/flink/connectors/hive/HiveDialectQueryITCase.java:
##########
@@ -788,7 +788,7 @@ public void testCastTimeStampToDecimal() throws Exception {
timestamp))
.collect());
assertThat(results.toString())
- .isEqualTo(String.format("[+I[%s]]",
expectTimeStampDecimal.toFormatString(8)));
+ .isEqualTo(String.format("[+I[%s]]",
expectTimeStampDecimal));
Review Comment:
Yes, it's. But there's a special case when comes to cast constant and
constant fold is enabled. Actually, the current behavior is same to Hive.
I try with the following sql in Hive:
```sql
hive> select cast(cast('2012-12-19 11:12:19.1234567' as timestamp) as
decimal(30,8));
1355915539.1234567
hive> insert into t2 values('2012-12-19 11:12:19.1234567')
hive> select cast(c2 as decimal(30, 8)) from t2;
1355915539.12345670
hive > insert into t1 select * from t2;
hive > select * from t1;
1355915539.12345670
```
The plan for the sql in hive `select cast(cast('2012-12-19 11:12:19.1234567'
as timestamp) as decimal(30,8))` is:
```sql
STAGE PLANS:
Stage: Stage-0
Fetch Operator
limit: -1
Processor Tree:
TableScan
alias: _dummy_table
Row Limit Per Split: 1
Statistics: Num rows: 1 Data size: 10 Basic stats: COMPLETE Column
stats: COMPLETE
Select Operator
expressions: 1355915539.1234567 (type: decimal(30,8))
outputColumnNames: _col0
Statistics: Num rows: 1 Data size: 112 Basic stats: COMPLETE
Column stats: COMPLETE
ListSink
```
The plan for `select cast(c1 as decimal(30, 8)) from t1` is :
```sql
STAGE DEPENDENCIES:
Stage-0 is a root stage
STAGE PLANS:
Stage: Stage-0
Fetch Operator
limit: -1
Processor Tree:
TableScan
alias: t1
Statistics: Num rows: 1 Data size: 112 Basic stats: COMPLETE
Column stats: NONE
Select Operator
expressions: CAST( c1 AS decimal(30,8)) (type: decimal(30,8))
outputColumnNames: _col0
Statistics: Num rows: 1 Data size: 112 Basic stats: COMPLETE
Column stats: NONE
ListSink
```
The reason I found is the `HiveDecimalConverter` used to convert data in
Hive's `GenericUDFToDecimal` function actually won't padding zero for
`2012-12-19 11:12:19.1234567`, althogh the type is ` decimal(30,8)`.
Then, the first sql will select a constant `1355915539.1234567`.
But for the second sql, a further padding will be done which will result
`1355915539.12345670`.
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