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https://issues.apache.org/jira/browse/DRILL-6768?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16656648#comment-16656648
]
ASF GitHub Bot commented on DRILL-6768:
---------------------------------------
vdiravka commented on a change in pull request #1494: DRILL-6768: Improve
to_date, to_time and to_timestamp and correspondi…
URL: https://github.com/apache/drill/pull/1494#discussion_r226455956
##########
File path:
exec/java-exec/src/main/codegen/templates/DateIntervalFunctionTemplates/EmptyStringToDateTypeFunctions.java
##########
@@ -0,0 +1,78 @@
+/*
+ * 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.
+ */
+import org.apache.drill.exec.expr.annotations.Workspace;
+
+<@pp.dropOutputFile />
+
+<#list dateIntervalFunc.emptyStringToDateConversion as conversion>
+
+<@pp.changeOutputFile
name="/org/apache/drill/exec/expr/fn/impl/G${conversion.from}To${conversion.to}.java"
/>
+
+<#include "/@includes/license.ftl" />
+
+ package org.apache.drill.exec.expr.fn.impl;
+
+ import org.apache.drill.exec.expr.DrillSimpleFunc;
+ import org.apache.drill.exec.expr.annotations.FunctionTemplate;
+ import
org.apache.drill.exec.expr.annotations.FunctionTemplate.NullHandling;
+ import org.apache.drill.exec.expr.annotations.Output;
+ import org.apache.drill.exec.expr.annotations.Workspace;
+ import org.apache.drill.exec.expr.annotations.Param;
+ import org.apache.drill.exec.expr.holders.*;
+ import org.apache.drill.exec.record.RecordBatch;
+
+/*
+ * This class is generated using freemarker and the ${.template_name} template.
+ */
+@FunctionTemplate(name = "convert${conversion.from}To${conversion.to}", scope
= FunctionTemplate.FunctionScope.SIMPLE, nulls = NullHandling.INTERNAL)
Review comment:
I think `NULL_IF_NULL` mode fits better these functions (allows to skip
functions `eval` blocks in case of null inputs), but I found that it doesn't
work for your case with empty input VarChar `""`. Not sure that it is expected.
If `NULL_IF_NULL` means null output value if and only if null input, then
everything is ok, but it should be described better only.
But looks like null outputs for non null inputs could be allowed in [some
cases](https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/DrillSimpleFuncHolder.java#L143).
I will describe it in more detail.
I have tried to use `NULL_IF_NULL` mode for your function
`castEmptyStringNullableVarCharToNULLABLEDATE` for 3 input VarChar values:
1. "1997-12-10"
2. null
3. ""
1 and 2 cases for work as intended. But for 3 case the logic for proper
output from the function is performed as intended:
```
if (in.isSet == 0 || in.end == in.start) {
out.isSet = 0;
break CastNullableVarCharNullableVarCharToNullableDate_eval;
}
```
and then additional logic is added right after the previous one:
```
CastNullableVarCharNullableVarCharToNullableDate_eval: {
if (in.isSet == 0 || in.end == in.start) {
out.isSet = 0;
break CastNullableVarCharNullableVarCharToNullableDate_eval;
}
out.isSet = 1;
out.value =
org.apache.drill.exec.expr.fn.impl.StringFunctionHelpers.getDate(in.buffer,
in.start, in.end);
}
out.isSet = 1;
out4 = out;
out.isSet = 1;
```
[This
code](https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/DrillSimpleFuncHolder.java#L143)
is [duplicated
here](https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/DrillSimpleFuncHolder.java#L147).
Looks like second statement is redundant and first one along with a comment is
questionable.
It sets the output to 1, so it means non-nullable output in any case and
consequently `1970-01-01` output date for "" input VarChar.
Or am I missed something here?
We can consider 3 ways here:
to update javadoc to reflect this:
> NULL output if and only if NULL input
or to ask community, or to open the Jira ticket.
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> Improve to_date, to_time and to_timestamp and corresponding cast functions to
> handle empty string when `drill.exec.functions.cast_empty_string_to_null`
> option is enabled
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: DRILL-6768
> URL: https://issues.apache.org/jira/browse/DRILL-6768
> Project: Apache Drill
> Issue Type: Improvement
> Affects Versions: 1.14.0
> Reporter: Bohdan Kazydub
> Assignee: Bohdan Kazydub
> Priority: Major
> Labels: doc-impacting
> Fix For: 1.15.0
>
>
> When `drill.exec.functions.cast_empty_string_to_null` option is enabled
> `to_date`, `to_time` and `to_timestamp` functions while converting string to
> according type in case if null or empty string values are passed will return
> NULL (to avoid CASE clauses which are littering a query and will work in
> accordance with their respective CAST counterparts) for both cases.
>
>
>
> CASTs will be handled in a similar way (uniformly with numeric types):
>
> ||Value to cast||Now||Will be||
> |NULL|NULL|NULL|
> |'' (empty string)|Error in many cases (except numerical types)|NULL|
> CAST empty string to null (in case of enabled option) will be supported by
> DATE, TIME, TIMESTAMP, INTERVAL YEAR, INTERVAL MONTH and INTERVAL DAY
> functions in addition to numeric types.
>
> *For documentation*
> TBA
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