slinkydeveloper commented on a change in pull request #18582:
URL: https://github.com/apache/flink/pull/18582#discussion_r797372485



##########
File path: 
flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/functions/casting/NumericToTimestampCastRule.java
##########
@@ -0,0 +1,67 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.planner.functions.casting;
+
+import org.apache.flink.table.api.ValidationException;
+import org.apache.flink.table.data.TimestampData;
+import org.apache.flink.table.types.logical.LogicalType;
+import org.apache.flink.table.types.logical.LogicalTypeFamily;
+import org.apache.flink.table.types.logical.LogicalTypeRoot;
+
+/**
+ * {@link LogicalTypeFamily#NUMERIC} to {@link 
LogicalTypeRoot#TIMESTAMP_WITHOUT_TIME_ZONE}/{@link
+ * LogicalTypeRoot#TIMESTAMP_WITH_LOCAL_TIME_ZONE} cast rule. Disable cast 
conversion between
+ * Numeric type and Timestamp type and suggest to use {@code 
TO_TIMESTAMP()}/{@code
+ * TO_TIMESTAMP_LTZ()} instead.
+ */
+class NumericToTimestampCastRule
+        extends AbstractExpressionCodeGeneratorCastRule<Number, TimestampData> 
{
+
+    static final NumericToTimestampCastRule INSTANCE = new 
NumericToTimestampCastRule();
+
+    private NumericToTimestampCastRule() {
+        super(
+                CastRulePredicate.builder()
+                        .input(LogicalTypeFamily.NUMERIC)
+                        .target(LogicalTypeRoot.TIMESTAMP_WITHOUT_TIME_ZONE)
+                        .target(LogicalTypeRoot.TIMESTAMP_WITH_LOCAL_TIME_ZONE)
+                        .build());
+    }
+
+    @Override
+    public String generateExpression(
+            CodeGeneratorCastRule.Context context,
+            String inputTerm,
+            LogicalType inputLogicalType,
+            LogicalType targetLogicalType) {
+        if (targetLogicalType.is(LogicalTypeRoot.TIMESTAMP_WITHOUT_TIME_ZONE)) 
{
+            throw new ValidationException(
+                    "The cast conversion from NUMERIC type to TIMESTAMP type"
+                            + " is not allowed, it's recommended to use 
TO_TIMESTAMP(FROM_UNIXTIME(numeric_col))"
+                            + " instead, note the numeric is in seconds.");
+        } else if 
(targetLogicalType.is(LogicalTypeRoot.TIMESTAMP_WITH_LOCAL_TIME_ZONE)) {
+            throw new ValidationException(
+                    "The cast conversion from NUMERIC type"
+                            + " to TIMESTAMP_LTZ type is not allowed, it's 
recommended to use"
+                            + " TO_TIMESTAMP_LTZ(numeric_col, precision) 
instead.");
+        } else {
+            throw new IllegalArgumentException("This is a bug. Please file an 
issue.");
+        }

Review comment:
       Given we're touching this, can we move this to somewhere like 
`LogicalTypeCasts` or similar where it better belongs to? Given we're also 
ending up linking `LogicalTypeCasts` with calcite 
(https://github.com/apache/flink/pull/18524/files#diff-8c1c5cdfd4ee1de9d54fd39db308ab1d7fa9fddb2db1e36cdd1c9b0b8fc90f4bR173),
 we could have a method there like `getFailureMessage(LogicalType in, 
LogicalType out)` or similar which contains all the logic for the special 
"error messages" for cast tuples not matching.
   
   Also the problem with failing in the rule is that we assume all around the 
code that `generate` never fails if `exists()` returns true for that rule, so 
i'm not sure if this is safe to do.

##########
File path: 
flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/functions/casting/TimestampToDateCastRule.java
##########
@@ -0,0 +1,68 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.planner.functions.casting;
+
+import org.apache.flink.table.data.TimestampData;
+import org.apache.flink.table.planner.codegen.calls.BuiltInMethods;
+import org.apache.flink.table.types.logical.LogicalType;
+import org.apache.flink.table.types.logical.LogicalTypeRoot;
+import org.apache.flink.table.utils.DateTimeUtils;
+
+import static 
org.apache.flink.table.planner.functions.casting.CastRuleUtils.methodCall;
+import static 
org.apache.flink.table.planner.functions.casting.CastRuleUtils.staticCall;
+
+/**
+ * {@link LogicalTypeRoot#TIMESTAMP_WITHOUT_TIME_ZONE}/{@link
+ * LogicalTypeRoot#TIMESTAMP_WITH_LOCAL_TIME_ZONE} to {@link 
LogicalTypeRoot#DATE}.
+ */
+class TimestampToDateCastRule
+        extends AbstractExpressionCodeGeneratorCastRule<TimestampData, Number> 
{
+
+    static final TimestampToDateCastRule INSTANCE = new 
TimestampToDateCastRule();
+
+    private TimestampToDateCastRule() {
+        super(
+                CastRulePredicate.builder()
+                        .input(LogicalTypeRoot.TIMESTAMP_WITHOUT_TIME_ZONE)
+                        .input(LogicalTypeRoot.TIMESTAMP_WITH_LOCAL_TIME_ZONE)
+                        .target(LogicalTypeRoot.DATE)
+                        .build());
+    }
+
+    @Override
+    public String generateExpression(
+            CodeGeneratorCastRule.Context context,
+            String inputTerm,
+            LogicalType inputLogicalType,
+            LogicalType targetLogicalType) {
+
+        if (inputLogicalType.is(LogicalTypeRoot.TIMESTAMP_WITHOUT_TIME_ZONE)) {
+            return CastRuleUtils.cast(

Review comment:
       static import `cast` and other methods of `CastRuleUtils` whenever is 
possible

##########
File path: 
flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/functions/casting/CastRuleUtils.java
##########
@@ -43,6 +43,10 @@ static String nullLiteral(boolean legacyBehaviour) {
         return legacyBehaviour ? strLiteral("null") : strLiteral("NULL");
     }
 
+    static String operator(String operator, Object argLeft, Object argRight) {

Review comment:
       Can we use "left", "operator", "right" rather than the infix?

##########
File path: 
flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/functions/casting/TimestampToTimeCastRule.java
##########
@@ -54,9 +56,11 @@ public String generateExpression(
             LogicalType targetLogicalType) {
 
         if (inputLogicalType.is(LogicalTypeRoot.TIMESTAMP_WITHOUT_TIME_ZONE)) {
-            return CastRuleUtils.cast(
+            return cast(
                     "int",
-                    methodCall(inputTerm, "getMillisecond") + "%" + 
DateTimeUtils.MILLIS_PER_DAY);
+                    operator(
+                            "%s",

Review comment:
       typo with the `s`?

##########
File path: 
flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/functions/casting/TimestampToDateCastRule.java
##########
@@ -0,0 +1,68 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.planner.functions.casting;
+
+import org.apache.flink.table.data.TimestampData;
+import org.apache.flink.table.planner.codegen.calls.BuiltInMethods;
+import org.apache.flink.table.types.logical.LogicalType;
+import org.apache.flink.table.types.logical.LogicalTypeRoot;
+import org.apache.flink.table.utils.DateTimeUtils;
+
+import static 
org.apache.flink.table.planner.functions.casting.CastRuleUtils.methodCall;
+import static 
org.apache.flink.table.planner.functions.casting.CastRuleUtils.staticCall;
+
+/**
+ * {@link LogicalTypeRoot#TIMESTAMP_WITHOUT_TIME_ZONE}/{@link
+ * LogicalTypeRoot#TIMESTAMP_WITH_LOCAL_TIME_ZONE} to {@link 
LogicalTypeRoot#DATE}.
+ */
+class TimestampToDateCastRule
+        extends AbstractExpressionCodeGeneratorCastRule<TimestampData, Number> 
{
+
+    static final TimestampToDateCastRule INSTANCE = new 
TimestampToDateCastRule();
+
+    private TimestampToDateCastRule() {
+        super(
+                CastRulePredicate.builder()
+                        .input(LogicalTypeRoot.TIMESTAMP_WITHOUT_TIME_ZONE)
+                        .input(LogicalTypeRoot.TIMESTAMP_WITH_LOCAL_TIME_ZONE)
+                        .target(LogicalTypeRoot.DATE)
+                        .build());
+    }
+
+    @Override
+    public String generateExpression(
+            CodeGeneratorCastRule.Context context,
+            String inputTerm,
+            LogicalType inputLogicalType,
+            LogicalType targetLogicalType) {
+
+        if (inputLogicalType.is(LogicalTypeRoot.TIMESTAMP_WITHOUT_TIME_ZONE)) {
+            return CastRuleUtils.cast(
+                    "int",
+                    methodCall(inputTerm, "getMillisecond") + "/" + 
DateTimeUtils.MILLIS_PER_DAY);

Review comment:
       Can you have this `getMillisecond` method in `BuiltInMethods`?




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