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https://issues.apache.org/jira/browse/CALCITE-2928?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16803610#comment-16803610
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Danny Chan edited comment on CALCITE-2928 at 3/28/19 6:11 AM:
--------------------------------------------------------------

[~julianhyde] i have fire a 
[PR#1137|https://github.com/apache/calcite/pull/1137]

Initially i want to change both builtin operators and UDFs case sensitive 
internal, and control the case-sensitiveness through config parser config[2].

The problems i encounter when doing this patch:
 1.There is a SqlAbstractParserImpl which extended by all the SqlParser, so 
there is no chance to see the case-sensitiveness when parsing the builtin 
operators in SqlStdOperatorTable[1], and i have to hard code the 
case-sensitiveness to be false.
 2. Because of 1 i have to make the 
ReflectiveSqlOperatorTable#lookupOperatorOverloads case-insensitive for 
SqlStdOperatorTable(use instance of to detect).

So with this patch, we can control both table/column/UDF name with 
SqlParser.Config.caseSensitive(this flag can be configured through connection 
property or FrameworkConfig).

But for builtins, they behave all case-insensitively, just like before.

BTW, this patch add the flag in SqlOperatorTable#lookupOperatorOverloads, so 
many codes are touched, i kind of thought the SqlOperatorTable is also 
pluggable, if we create another case-insensitive ListSqlOperatorTable can also 
make another choice for users. And this will make minor change.

[1] 
[link1|https://github.com/apache/calcite/blob/3124a85b93ff2f1b79484c7bd4cc41835d4f1920/core/src/main/java/org/apache/calcite/sql/parser/SqlAbstractParserImpl.java#L395]
 [2] 
[link2|https://github.com/apache/calcite/blob/3124a85b93ff2f1b79484c7bd4cc41835d4f1920/core/src/main/java/org/apache/calcite/sql/parser/SqlParser.java#L221]


was (Author: danny0405):
[~julianhyde] i have fire a 
[PR#1137|https://github.com/apache/calcite/pull/1137]

Initially i wanna change both builtin operators and UDFs case sensitive 
internal, and control the case-sensitiveness through config parser config[2].

The problems i encounter when doing this patch:
 1.There is a SqlAbstractParserImpl which extended by all the SqlParser, so 
there is no change to see the case-sensitivless when parsing the builtin 
operators in SqlStdOperatorTable[1], and i have to hard code the case 
sensitiveness to be false.
 2. Because of 1 i have to make the 
ReflectiveSqlOperatorTable#lookupOperatorOverloads case- insensitive for 
SqlStdOperatorTable(use instance of to detect).

So with this patch, we can control both table/column/UDF name with 
SqlParser.Config.caseSensitive(this flag can be configured through connection 
property or FrameworkConfig).

But for builtins, they behave all case-insensitively, just like before.

BTW, this patch add the flag in SqlOperatorTable#lookupOperatorOverloads, so 
many codes are touched, i kind of thought the SqlOperatorTable is also 
plugable, if we create a case-insensitive ListSqlOperatorTable can also make 
another choice for users. And this will make minor change.

[1] 
[link1|https://github.com/apache/calcite/blob/3124a85b93ff2f1b79484c7bd4cc41835d4f1920/core/src/main/java/org/apache/calcite/sql/parser/SqlAbstractParserImpl.java#L395]
 [2] 
[link2|https://github.com/apache/calcite/blob/3124a85b93ff2f1b79484c7bd4cc41835d4f1920/core/src/main/java/org/apache/calcite/sql/parser/SqlParser.java#L221]

> Make UDF lookup default to case insensitive
> -------------------------------------------
>
>                 Key: CALCITE-2928
>                 URL: https://issues.apache.org/jira/browse/CALCITE-2928
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 1.19.0
>            Reporter: Danny Chan
>            Assignee: Danny Chan
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.20.0
>
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> Now for Calcite, we make default parser config unquotedCasing to 
> Lex.ORACLE.unquotedCasing(to uppercase)[1], and caseSensitive to 
> Lex.ORACLE.caseSensitive(case sensitive true).
> So if we have a UDAF named my_func and query with sql like:
> {code:java}
> select f0, my_func(f1) from table1 group by f0;
> {code}
> We would got a unparsed sql:
> {code:java}
> SELECT F0, MY_FUNC(F1) FROM TABLE1 GROUP BY F0;
> {code}
> For CalciteCatalogReader we hard code the function look up to case sensitive 
> true[2],
> For ListSqlOperatorTable we make the operator name lookup case sensitive 
> true[3].
> For ReflectiveSqlOperatorTable, we make built-in operators 
> case-insensitively[4].
> For most of the cases, we use ListSqlOperatorTable to register our UDFs[5] 
> chained with SqlStdOperatorTable(which composite a ChainedSqlOperatorTable), 
> which finally passed to CalciteCatalogReader for validation.
> So there are some questions i have:
> 1. Why we make built-in operators look up case-insensitively while 
> ListSqlOperatorTable(for UDFs) case-sensitively, with default unquotedCasing 
> of TO_UPPERCASE.
> 2. What is the usage of CalciteCatalogReader#lookupOperatorOverloads i only 
> saw it used in a unit test LookupOperatorOverloadsTest.
> It seems that make UDF look up case-sensitively does not make any sense, 
> users will never distinguish their function with just word cases. And i 
> checked also MYSQL, ORACLE, POSTGRES, their UDFs are all registered 
> case-insensitively.
> [1] 
> https://github.com/apache/calcite/blob/ffca956be03a99cd11e440d652b09674aaa727e6/core/src/main/java/org/apache/calcite/sql/parser/SqlParser.java#L231
> [2] 
> https://github.com/apache/calcite/blob/ffca956be03a99cd11e440d652b09674aaa727e6/core/src/main/java/org/apache/calcite/prepare/CalciteCatalogReader.java#L166
> [3] 
> https://github.com/apache/calcite/blob/ffca956be03a99cd11e440d652b09674aaa727e6/core/src/main/java/org/apache/calcite/sql/util/ListSqlOperatorTable.java#L63
> [4] 
> https://github.com/apache/calcite/blob/ffca956be03a99cd11e440d652b09674aaa727e6/core/src/main/java/org/apache/calcite/sql/util/ReflectiveSqlOperatorTable.java#L103
> [5] 
> https://github.com/apache/calcite/blob/ffca956be03a99cd11e440d652b09674aaa727e6/core/src/test/java/org/apache/calcite/test/MockSqlOperatorTable.java#L46



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