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From paul-rogers <...@git.apache.org>
Subject [GitHub] drill pull request #581: DRILL-4864: Add ANSI format for date/time functions
Date Thu, 12 Jan 2017 21:28:19 GMT
Github user paul-rogers commented on a diff in the pull request:

    https://github.com/apache/drill/pull/581#discussion_r95871016
  
    --- Diff: exec/java-exec/src/main/codegen/templates/DateIntervalFunctionTemplates/SqlToDateTypeFunctions.java
---
    @@ -0,0 +1,77 @@
    +/**
    + * 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.dates as type>
    +
    +<@pp.changeOutputFile name = "/org/apache/drill/exec/expr/fn/impl/SqlTo${type}.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.*;
    +
    +/*
    + * This class is generated using freemarker and the ${.template_name} template.
    + */
    +
    +@FunctionTemplate(name = "sql_to_${type?lower_case}",
    +                  scope = FunctionTemplate.FunctionScope.SIMPLE,
    +                  nulls = NullHandling.NULL_IF_NULL)
    +public class SqlTo${type} implements DrillSimpleFunc {
    +
    +    @Param  VarCharHolder left;
    +    @Param  VarCharHolder right;
    +    @Workspace org.joda.time.format.DateTimeFormatter format;
    +    @Output ${type}Holder out;
    +
    +    public void setup() {
    +        // Get the desired output format
    +        byte[] buf = new byte[right.end - right.start];
    +        right.buffer.getBytes(right.start, buf, 0, right.end - right.start);
    +        String formatString = new String(buf, com.google.common.base.Charsets.UTF_8);
    +        String pattern = org.apache.drill.common.expression.fn.JodaDateValidator.toJodaFormat(formatString);
    +        format = org.joda.time.format.DateTimeFormat.forPattern(pattern);
    +    }
    +
    +    public void eval() {
    +        // Get the input
    +        byte[] buf1 = new byte[left.end - left.start];
    +        left.buffer.getBytes(left.start, buf1, 0, left.end - left.start);
    +        String input = new String(buf1, com.google.common.base.Charsets.UTF_8);
    +
    +        <#if type == "Date">
    +        out.value = (org.joda.time.DateMidnight.parse(input, format).withZoneRetainFields(org.joda.time.DateTimeZone.UTC)).getMillis();
    +        <#elseif type == "TimeStamp">
    +        out.value = org.joda.time.DateTime.parse(input, format).withZoneRetainFields(org.joda.time.DateTimeZone.UTC).getMillis();
    +        <#elseif type == "Time">
    +        out.value = (int) ((format.parseDateTime(input)).withZoneRetainFields(org.joda.time.DateTimeZone.UTC).getMillis());
    +        </#if>
    --- End diff --
    
    Let's think about error handling. The input is a VarChar which can be anything: a blank
string, the name of a movie star, a phone number. The user claims it is a date. Even if it
is, it might be badly formed or in the wrong format.
    
    What error handling do we do? `doEval` declares no exceptions. According to the Joda Javadoc,
`parse()` will throw an (unchecked) `IllegalArgumentException` if the input is bad. This will
bubble up the execution stack and cause the fragment executor to fail. There will be no context
("row xyz of input abc"), and precious little information about the SQL statement and field
that caused the problem.
    
    Should we catch the exception and fill in as much context as we have available?


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