Exception parsing "SELECT @@character_set_server"

[Adolfo Ochagavía]

Hi there,

I am writing a MySQL-compatible server that talks the MySQL protocol. Some 
clients are sending special queries to autoconfigure themselves, like "SELECT 
@@character_set_server". I would like to use calcite to parse such queries, but 
parsing fails with an exception, seemingly related to the usage of "@@" in 
variable names. Is this unsupported or am I doing something wrong?

The code:
> var config = SqlParser.Config.DEFAULT.withLex(Lex.MYSQL);
> var parser = SqlParser.create("SELECT @@character_set_server", config);
> var parsed = parser.parseQuery();

The exception: org.apache.calcite.sql.parser.SqlParseException: Lexical error 
at line 1, column 9.  Encountered: "@" (64), after : ""

Any help is appreciated!
Adolfo

Re: Exception parsing "SELECT @@character_set_server"

[Julian Hyde]

The ‘@@‘ prefix is not standard SQL, and Calcite does not support it.

Can you do some research to find out how MySQL handles it. Is it considered to 
be part of the variable name? Or is it a prefix (like $ in bash) that means 
‘what comes next is a variable’? In other words, does the parser say there is a 
reference to a variable called '@@character_set_server’ or a variable called 
‘character_set_server’? And is ‘@‘ a legal part of a variable name?

Also, is it handled by the core SQL parser or by a preprocessor?

Julian


> On Mar 22, 2022, at 2:17 AM, Adolfo Ochagavía  wrote:
> 
> Hi there,
> 
> I am writing a MySQL-compatible server that talks the MySQL protocol. Some 
> clients are sending special queries to autoconfigure themselves, like "SELECT 
> @@character_set_server". I would like to use calcite to parse such queries, 
> but parsing fails with an exception, seemingly related to the usage of "@@" 
> in variable names. Is this unsupported or am I doing something wrong?
> 
> The code:
>> var config = SqlParser.Config.DEFAULT.withLex(Lex.MYSQL);
>> var parser = SqlParser.create("SELECT @@character_set_server", config);
>> var parsed = parser.parseQuery();
> 
> The exception: org.apache.calcite.sql.parser.SqlParseException: Lexical error 
> at line 1, column 9.  Encountered: "@" (64), after : ""
> 
> Any help is appreciated!
> Adolfo

Re: Exception parsing "SELECT @@character_set_server"

[Justin Swanhart]

MySQL support two categories of variables, user variables which are
prefixed with the @character and session/global SERVER variables which are
prefixed with @@.

You can also access them via:

Select @@session.session_var;
Select @@global.global_var;
select @@session_or_global_var;

for example:
mysql> select @@warp_adjust_table_stats_for_joins;
+-+
| @@warp_adjust_table_stats_for_joins |
+-+
|   1 |
+-+
1 row in set (0.00 sec)

mysql> set warp_adjust_table_stats_for_joins= false;
Query OK, 0 rows affected (0.00 sec)

mysql> select @@warp_adjust_table_stats_for_joins;
+-+
| @@warp_adjust_table_stats_for_joins |
+-+
|   0 |
+-+
1 row in set (0.00 sec)

mysql> select @@session.warp_adjust_table_stats_for_joins;
+-+
| @@session.warp_adjust_table_stats_for_joins |
+-+
|   0 |
+-+
1 row in set (0.00 sec)

mysql> select @@global.warp_adjust_table_stats_for_joins;
++
| @@global.warp_adjust_table_stats_for_joins |
++
|  1 |
++
1 row in set (0.00 sec)


On Tue, Mar 22, 2022 at 5:02 PM Julian Hyde  wrote:

> The ‘@@‘ prefix is not standard SQL, and Calcite does not support it.
>
> Can you do some research to find out how MySQL handles it. Is it
> considered to be part of the variable name? Or is it a prefix (like $ in
> bash) that means ‘what comes next is a variable’? In other words, does the
> parser say there is a reference to a variable called
> '@@character_set_server’ or a variable called ‘character_set_server’? And
> is ‘@‘ a legal part of a variable name?
>
> Also, is it handled by the core SQL parser or by a preprocessor?
>
> Julian
>
>
> > On Mar 22, 2022, at 2:17 AM, Adolfo Ochagavía 
> wrote:
> >
> > Hi there,
> >
> > I am writing a MySQL-compatible server that talks the MySQL protocol.
> Some clients are sending special queries to autoconfigure themselves, like
> "SELECT @@character_set_server". I would like to use calcite to parse such
> queries, but parsing fails with an exception, seemingly related to the
> usage of "@@" in variable names. Is this unsupported or am I doing
> something wrong?
> >
> > The code:
> >> var config = SqlParser.Config.DEFAULT.withLex(Lex.MYSQL);
> >> var parser = SqlParser.create("SELECT @@character_set_server", config);
> >> var parsed = parser.parseQuery();
> >
> > The exception: org.apache.calcite.sql.parser.SqlParseException: Lexical
> error at line 1, column 9.  Encountered: "@" (64), after : ""
> >
> > Any help is appreciated!
> > Adolfo
>
>

Re: Exception parsing "SELECT @@character_set_server"

[Julian Hyde]

A couple more questions. Do these variables have well-defined types? Do they 
have to be valid expressions? If the answer to either of these questions is 
’no’ then maybe they are what Oracle calls ’substitution variables’. 
Substitution variables have a behavior more like C macros than real variables 
and we would not be able to handle them easily.

Julian

[1] 
https://blogs.oracle.com/opal/post/sql*plus-substitution-variables-define-variables-and-parameters-in-sql-queries#2
 

 

> On Mar 28, 2022, at 12:02 PM, Julian Hyde  wrote:
> 
> We’d be open to adding support, but it must not be the default behavior, so 
> there will be need to be some kind of flag.
> 
> Can you log a JIRA case with the subject ’Support variables with “@" and “@@" 
> prefixes (like MySQL)’. Then we can write a specification and you can submit 
> a pull request.
> 
> At the RexNode level I think there are already constructs for referencing 
> variables to this change would be confined to the parser.  
> 
> Julian
> 
> 
>> On Mar 28, 2022, at 4:04 AM, Adolfo Ochagavía > > wrote:
>> 
>> Would you be open to a patch to add proper support for this kind of MySQL 
>> variables, or do you consider it to be outside the scope of Calcite?
>> 
>> On 2022/03/22 21:52:09 Justin Swanhart wrote:
>>> MySQL support two categories of variables, user variables which are
>>> prefixed with the @character and session/global SERVER variables which are
>>> prefixed with @@.
>>> 
>>> You can also access them via:
>>> 
>>> Select @@session.session_var;
>>> Select @@global.global_var;
>>> select @@session_or_global_var;
>>> 
>>> for example:
>>> mysql> select @@warp_adjust_table_stats_for_joins;
>>> +-+
>>> | @@warp_adjust_table_stats_for_joins |
>>> +-+
>>> | 1 |
>>> +-+
>>> 1 row in set (0.00 sec)
>>> 
>>> mysql> set warp_adjust_table_stats_for_joins= false;
>>> Query OK, 0 rows affected (0.00 sec)
>>> 
>>> mysql> select @@warp_adjust_table_stats_for_joins;
>>> +-+
>>> | @@warp_adjust_table_stats_for_joins |
>>> +-+
>>> | 0 |
>>> +-+
>>> 1 row in set (0.00 sec)
>>> 
>>> mysql> select @@session.warp_adjust_table_stats_for_joins;
>>> +-+
>>> | @@session.warp_adjust_table_stats_for_joins |
>>> +-+
>>> | 0 |
>>> +-+
>>> 1 row in set (0.00 sec)
>>> 
>>> mysql> select @@global.warp_adjust_table_stats_for_joins;
>>> ++
>>> | @@global.warp_adjust_table_stats_for_joins |
>>> ++
>>> | 1 |
>>> ++
>>> 1 row in set (0.00 sec)
>>> 
>>> 
>>> On Tue, Mar 22, 2022 at 5:02 PM Julian Hyde >> > wrote:
>>> 
 The ‘@@‘ prefix is not standard SQL, and Calcite does not support it.
 
 Can you do some research to find out how MySQL handles it. Is it
 considered to be part of the variable name? Or is it a prefix (like $ in
 bash) that means ‘what comes next is a variable’? In other words, does the
 parser say there is a reference to a variable called
 '@@character_set_server’ or a variable called ‘character_set_server’? And
 is ‘@‘ a legal part of a variable name?
 
 Also, is it handled by the core SQL parser or by a preprocessor?
 
 Julian
 
 
> On Mar 22, 2022, at 2:17 AM, Adolfo Ochagavía  >
 wrote:
> 
> Hi there,
> 
> I am writing a MySQL-compatible server that talks the MySQL protocol.
 Some clients are sending special queries to autoconfigure themselves, like
 "SELECT @@character_set_server". I would like to use calcite to parse such
 queries, but parsing fails with an exception, seemingly related to the
 usage of "@@" in variable names. Is this unsupported or am I doing
 something wrong?
> 
> The code:
>> var config = SqlParser.Config.DEFAULT.withLex(Lex.MYSQL);
>> var parser = SqlParser.create("SELECT @@character_set_server", config);
>> var parsed = parser.parseQuery();
> 
> The exception: org.apache.calcite.sql.parser.SqlParseException: Lexical
 error at line 1, column 9. Encountered: "@" (64), after : ""
> 
> Any help is appreciated!
> Adolfo
> 

Re: Exception parsing "SELECT @@character_set_server"

[Julian Hyde]

We’d be open to adding support, but it must not be the default behavior, so 
there will be need to be some kind of flag.

Can you log a JIRA case with the subject ’Support variables with “@" and “@@" 
prefixes (like MySQL)’. Then we can write a specification and you can submit a 
pull request.

At the RexNode level I think there are already constructs for referencing 
variables to this change would be confined to the parser.  

Julian


> On Mar 28, 2022, at 4:04 AM, Adolfo Ochagavía  wrote:
> 
> Would you be open to a patch to add proper support for this kind of MySQL 
> variables, or do you consider it to be outside the scope of Calcite?
> 
> On 2022/03/22 21:52:09 Justin Swanhart wrote:
>> MySQL support two categories of variables, user variables which are
>> prefixed with the @character and session/global SERVER variables which are
>> prefixed with @@.
>> 
>> You can also access them via:
>> 
>> Select @@session.session_var;
>> Select @@global.global_var;
>> select @@session_or_global_var;
>> 
>> for example:
>> mysql> select @@warp_adjust_table_stats_for_joins;
>> +-+
>> | @@warp_adjust_table_stats_for_joins |
>> +-+
>> | 1 |
>> +-+
>> 1 row in set (0.00 sec)
>> 
>> mysql> set warp_adjust_table_stats_for_joins= false;
>> Query OK, 0 rows affected (0.00 sec)
>> 
>> mysql> select @@warp_adjust_table_stats_for_joins;
>> +-+
>> | @@warp_adjust_table_stats_for_joins |
>> +-+
>> | 0 |
>> +-+
>> 1 row in set (0.00 sec)
>> 
>> mysql> select @@session.warp_adjust_table_stats_for_joins;
>> +-+
>> | @@session.warp_adjust_table_stats_for_joins |
>> +-+
>> | 0 |
>> +-+
>> 1 row in set (0.00 sec)
>> 
>> mysql> select @@global.warp_adjust_table_stats_for_joins;
>> ++
>> | @@global.warp_adjust_table_stats_for_joins |
>> ++
>> | 1 |
>> ++
>> 1 row in set (0.00 sec)
>> 
>> 
>> On Tue, Mar 22, 2022 at 5:02 PM Julian Hyde > > wrote:
>> 
>>> The ‘@@‘ prefix is not standard SQL, and Calcite does not support it.
>>> 
>>> Can you do some research to find out how MySQL handles it. Is it
>>> considered to be part of the variable name? Or is it a prefix (like $ in
>>> bash) that means ‘what comes next is a variable’? In other words, does the
>>> parser say there is a reference to a variable called
>>> '@@character_set_server’ or a variable called ‘character_set_server’? And
>>> is ‘@‘ a legal part of a variable name?
>>> 
>>> Also, is it handled by the core SQL parser or by a preprocessor?
>>> 
>>> Julian
>>> 
>>> 
 On Mar 22, 2022, at 2:17 AM, Adolfo Ochagavía >>> >
>>> wrote:
 
 Hi there,
 
 I am writing a MySQL-compatible server that talks the MySQL protocol.
>>> Some clients are sending special queries to autoconfigure themselves, like
>>> "SELECT @@character_set_server". I would like to use calcite to parse such
>>> queries, but parsing fails with an exception, seemingly related to the
>>> usage of "@@" in variable names. Is this unsupported or am I doing
>>> something wrong?
 
 The code:
> var config = SqlParser.Config.DEFAULT.withLex(Lex.MYSQL);
> var parser = SqlParser.create("SELECT @@character_set_server", config);
> var parsed = parser.parseQuery();
 
 The exception: org.apache.calcite.sql.parser.SqlParseException: Lexical
>>> error at line 1, column 9. Encountered: "@" (64), after : ""
 
 Any help is appreciated!
 Adolfo

Re: Exception parsing "SELECT @@character_set_server"

[Justin Swanhart]

Hi,

They are strongly typed.  Many are strings that can only be set to certain
legal values (like optmizer_switch).  These variables can also be used in
MySQL SET statements.  Note that there is no way to easily type the
variables except by examining their values, in the performance_schema (at
least in 8.0).  MySQL has some special values like ON
(set @@session.unique_checks=ON).  1 and 0 are supported in place of ON or
OFF.

There are 652 global variables in MySQL 8.0.27 enumerated in the attached
fiddle.  Each MySQL version adds (and sometimes removes) global variables
so this is probably hard to maintain on the Calcite side except to maybe
have some generic support for a MySQL global variable.

[1]
https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=639e08374d2218ab85e16d8210538d88

On Mon, Mar 28, 2022 at 3:08 PM Julian Hyde  wrote:

> A couple more questions. Do these variables have well-defined types? Do
> they have to be valid expressions? If the answer to either of these
> questions is ’no’ then maybe they are what Oracle calls ’substitution
> variables’. Substitution variables have a behavior more like C macros than
> real variables and we would not be able to handle them easily.
>
> Julian
>
> [1]
> https://blogs.oracle.com/opal/post/sql*plus-substitution-variables-define-variables-and-parameters-in-sql-queries#2
> <
> https://blogs.oracle.com/opal/post/sql*plus-substitution-variables-define-variables-and-parameters-in-sql-queries#2>
>
>
> > On Mar 28, 2022, at 12:02 PM, Julian Hyde 
> wrote:
> >
> > We’d be open to adding support, but it must not be the default behavior,
> so there will be need to be some kind of flag.
> >
> > Can you log a JIRA case with the subject ’Support variables with “@" and
> “@@" prefixes (like MySQL)’. Then we can write a specification and you can
> submit a pull request.
> >
> > At the RexNode level I think there are already constructs for
> referencing variables to this change would be confined to the parser.
> >
> > Julian
> >
> >
> >> On Mar 28, 2022, at 4:04 AM, Adolfo Ochagavía  > wrote:
> >>
> >> Would you be open to a patch to add proper support for this kind of
> MySQL variables, or do you consider it to be outside the scope of Calcite?
> >>
> >> On 2022/03/22 21:52:09 Justin Swanhart wrote:
> >>> MySQL support two categories of variables, user variables which are
> >>> prefixed with the @character and session/global SERVER variables which
> are
> >>> prefixed with @@.
> >>>
> >>> You can also access them via:
> >>>
> >>> Select @@session.session_var;
> >>> Select @@global.global_var;
> >>> select @@session_or_global_var;
> >>>
> >>> for example:
> >>> mysql> select @@warp_adjust_table_stats_for_joins;
> >>> +-+
> >>> | @@warp_adjust_table_stats_for_joins |
> >>> +-+
> >>> | 1 |
> >>> +-+
> >>> 1 row in set (0.00 sec)
> >>>
> >>> mysql> set warp_adjust_table_stats_for_joins= false;
> >>> Query OK, 0 rows affected (0.00 sec)
> >>>
> >>> mysql> select @@warp_adjust_table_stats_for_joins;
> >>> +-+
> >>> | @@warp_adjust_table_stats_for_joins |
> >>> +-+
> >>> | 0 |
> >>> +-+
> >>> 1 row in set (0.00 sec)
> >>>
> >>> mysql> select @@session.warp_adjust_table_stats_for_joins;
> >>> +-+
> >>> | @@session.warp_adjust_table_stats_for_joins |
> >>> +-+
> >>> | 0 |
> >>> +-+
> >>> 1 row in set (0.00 sec)
> >>>
> >>> mysql> select @@global.warp_adjust_table_stats_for_joins;
> >>> ++
> >>> | @@global.warp_adjust_table_stats_for_joins |
> >>> ++
> >>> | 1 |
> >>> ++
> >>> 1 row in set (0.00 sec)
> >>>
> >>>
> >>> On Tue, Mar 22, 2022 at 5:02 PM Julian Hyde  http://gmail.com/>> wrote:
> >>>
>  The ‘@@‘ prefix is not standard SQL, and Calcite does not support it.
> 
>  Can you do some research to find out how MySQL handles it. Is it
>  considered to be part of the variable name? Or is it a prefix (like $
> in
>  bash) that means ‘what comes next is a variable’? In other words,
> does the
>  parser say there is a reference to a variable called
>  '@@character_set_server’ or a variable called ‘character_set_server’?
> And
>  is ‘@‘ a legal part of a variable name?
> 
>  Also, is it handled by the core SQL parser or by a preprocessor?
> 
>  Julian
> 
> 
> > On Mar 22, 2022, at 2:17 AM, Adolfo Ochagavía  http://ochagavia.nl/>>
>  wrote:
> >
> > Hi there,
> >
> > I am writing a MySQL-compatible server that talks the MySQL protocol.
>  Some clients are sending special queries to autoconfigure themselves,
> 

Re: Exception parsing "SELECT @@character_set_server"

[Julian Hyde]

Thanks, Justin. For now, it’s enough to know that they have types.

If we hit the requirement that Calcite’s validator needs to know that (say) 
there is a variable called ‘FOO’ and its type is ’TIMESTAMP’ then we can use a 
plug-in map or even the SqlOperatorTable (modeling variables as functions with 
no arguments, kind of like CURRENT_TIMESTAMP today).   

> On Mar 28, 2022, at 1:52 PM, Justin Swanhart  wrote:
> 
> Hi,
> 
> They are strongly typed. Many are strings that can only be set to certain
> legal values (like optmizer_switch). These variables can also be used in
> MySQL SET statements. Note that there is no way to easily type the
> variables except by examining their values, in the performance_schema (at
> least in 8.0). MySQL has some special values like ON
> (set @@session.unique_checks=ON). 1 and 0 are supported in place of ON or
> OFF.
> 
> There are 652 global variables in MySQL 8.0.27 enumerated in the attached
> fiddle. Each MySQL version adds (and sometimes removes) global variables
> so this is probably hard to maintain on the Calcite side except to maybe
> have some generic support for a MySQL global variable.
> 
> [1]
> https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=639e08374d2218ab85e16d8210538d88 
> 
> 
> On Mon, Mar 28, 2022 at 3:08 PM Julian Hyde  > wrote:
> 
>> A couple more questions. Do these variables have well-defined types? Do
>> they have to be valid expressions? If the answer to either of these
>> questions is ’no’ then maybe they are what Oracle calls ’substitution
>> variables’. Substitution variables have a behavior more like C macros than
>> real variables and we would not be able to handle them easily.
>> 
>> Julian
>> 
>> [1]
>> https://blogs.oracle.com/opal/post/sql*plus-substitution-variables-define-variables-and-parameters-in-sql-queries#2
>> <
>> https://blogs.oracle.com/opal/post/sql*plus-substitution-variables-define-variables-and-parameters-in-sql-queries#2
>>  
>> >
>> 
>> 
>>> On Mar 28, 2022, at 12:02 PM, Julian Hyde 
>> wrote:
>>> 
>>> We’d be open to adding support, but it must not be the default behavior,
>> so there will be need to be some kind of flag.
>>> 
>>> Can you log a JIRA case with the subject ’Support variables with “@" and
>> “@@" prefixes (like MySQL)’. Then we can write a specification and you can
>> submit a pull request.
>>> 
>>> At the RexNode level I think there are already constructs for
>> referencing variables to this change would be confined to the parser.
>>> 
>>> Julian
>>> 
>>> 
 On Mar 28, 2022, at 4:04 AM, Adolfo Ochagavía > >> wrote:
 
 Would you be open to a patch to add proper support for this kind of
>> MySQL variables, or do you consider it to be outside the scope of Calcite?
 
 On 2022/03/22 21:52:09 Justin Swanhart wrote:
> MySQL support two categories of variables, user variables which are
> prefixed with the @character and session/global SERVER variables which
>> are
> prefixed with @@.
> 
> You can also access them via:
> 
> Select @@session.session_var;
> Select @@global.global_var;
> select @@session_or_global_var;
> 
> for example:
> mysql> select @@warp_adjust_table_stats_for_joins;
> +-+
> | @@warp_adjust_table_stats_for_joins |
> +-+
> | 1 |
> +-+
> 1 row in set (0.00 sec)
> 
> mysql> set warp_adjust_table_stats_for_joins= false;
> Query OK, 0 rows affected (0.00 sec)
> 
> mysql> select @@warp_adjust_table_stats_for_joins;
> +-+
> | @@warp_adjust_table_stats_for_joins |
> +-+
> | 0 |
> +-+
> 1 row in set (0.00 sec)
> 
> mysql> select @@session.warp_adjust_table_stats_for_joins;
> +-+
> | @@session.warp_adjust_table_stats_for_joins |
> +-+
> | 0 |
> +-+
> 1 row in set (0.00 sec)
> 
> mysql> select @@global.warp_adjust_table_stats_for_joins;
> ++
> | @@global.warp_adjust_table_stats_for_joins |
> ++
> | 1 |
> ++
> 1 row in set (0.00 sec)
> 
> 
> On Tue, Mar 22, 2022 at 5:02 PM Julian Hyde   <
>> http://gmail.com/ >> wrote:
> 
>> The ‘@@‘ prefix is not standard SQL, and Calcite does not support it.
>> 
>> 

RE: Re: Exception parsing "SELECT @@character_set_server"

[Adolfo Ochagavía]

Would you be open to a patch to add proper support for this kind of MySQL 
variables, or do you consider it to be outside the scope of Calcite?

On 2022/03/22 21:52:09 Justin Swanhart wrote:
> MySQL support two categories of variables, user variables which are
> prefixed with the @character and session/global SERVER variables which are
> prefixed with @@.
>
> You can also access them via:
>
> Select @@session.session_var;
> Select @@global.global_var;
> select @@session_or_global_var;
>
> for example:
> mysql> select @@warp_adjust_table_stats_for_joins;
> +-+
> | @@warp_adjust_table_stats_for_joins |
> +-+
> |   1 |
> +-+
> 1 row in set (0.00 sec)
>
> mysql> set warp_adjust_table_stats_for_joins= false;
> Query OK, 0 rows affected (0.00 sec)
>
> mysql> select @@warp_adjust_table_stats_for_joins;
> +-+
> | @@warp_adjust_table_stats_for_joins |
> +-+
> |   0 |
> +-+
> 1 row in set (0.00 sec)
>
> mysql> select @@session.warp_adjust_table_stats_for_joins;
> +-+
> | @@session.warp_adjust_table_stats_for_joins |
> +-+
> |   0 |
> +-+
> 1 row in set (0.00 sec)
>
> mysql> select @@global.warp_adjust_table_stats_for_joins;
> ++
> | @@global.warp_adjust_table_stats_for_joins |
> ++
> |  1 |
> ++
> 1 row in set (0.00 sec)
>
>
> On Tue, Mar 22, 2022 at 5:02 PM Julian Hyde  wrote:
>
> > The ‘@@‘ prefix is not standard SQL, and Calcite does not support it.
> >
> > Can you do some research to find out how MySQL handles it. Is it
> > considered to be part of the variable name? Or is it a prefix (like $ in
> > bash) that means ‘what comes next is a variable’? In other words, does the
> > parser say there is a reference to a variable called
> > '@@character_set_server’ or a variable called ‘character_set_server’? And
> > is ‘@‘ a legal part of a variable name?
> >
> > Also, is it handled by the core SQL parser or by a preprocessor?
> >
> > Julian
> >
> >
> > > On Mar 22, 2022, at 2:17 AM, Adolfo Ochagavía 
> > wrote:
> > >
> > > Hi there,
> > >
> > > I am writing a MySQL-compatible server that talks the MySQL protocol.
> > Some clients are sending special queries to autoconfigure themselves, like
> > "SELECT @@character_set_server". I would like to use calcite to parse such
> > queries, but parsing fails with an exception, seemingly related to the
> > usage of "@@" in variable names. Is this unsupported or am I doing
> > something wrong?
> > >
> > > The code:
> > >> var config = SqlParser.Config.DEFAULT.withLex(Lex.MYSQL);
> > >> var parser = SqlParser.create("SELECT @@character_set_server", config);
> > >> var parsed = parser.parseQuery();
> > >
> > > The exception: org.apache.calcite.sql.parser.SqlParseException: Lexical
> > error at line 1, column 9.  Encountered: "@" (64), after : ""
> > >
> > > Any help is appreciated!
> > > Adolfo
> >
> >
>