Jinfeng Ni created CALCITE-464:
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Summary: Make parser accept configurable max length for SQL
identifier
Key: CALCITE-464
URL: https://issues.apache.org/jira/browse/CALCITE-464
Project: Calcite
Issue Type: Improvement
Reporter: Jinfeng Ni
Assignee: Julian Hyde
Calcite currently uses 128 as the maximum length for sql identifier. We would
like to enhance the SQL parser, so that each system should be able to choose
its own identifier max length.
The following is the discussion copied from the dev mailing list:
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[Jinfeng]
Calcite (formly Optiq) has set the maximum length for an SQL identifier to 128.
This sounds quite reasonable for an ordinary sql identifier. However, for
system like Drill which allows user to query a file directly, it's quite likely
to run out of the allowed identifier length.
Drill allows the use case of :
select * from dfs.schema.`directory1/directory2/filename.json`;
The directory plus the filename is parsed as a SQL identifer. Since many file
system would allow file name up to 255 bytes [1], it's likely user could use an
identifier with more than 128 bytes when query the file directly.
I would like to ask the Calcite community whether there is any performance
impact if we bump up the maximum length for a SQL identifier. If there is
negligible performance impact, then, can we make the maximum length
configurable in the SQL parser? We could make slightly modification to
CombinedParser.jj template, to allow each system to set its own max length,
with default still being 128.
The approach to allow a configurable setting seems to be match what Postgres
[2] is doing, which allows the length to be "raised by changing the NAMEDATALEN
constant in src/include/pg_config_manual.h." [2]
[Julian]
Each system should be able to choose its own identifier max length.
I’d prefer to make it configurable at runtime. Then we can test it. Add an
extra parameter to SqlParser’s constructor, and have it call
parser.setIdentifierMaxLength, similar to how it calls setQuotedCasing right
now.
Or if you want to go further, create
interface SqlParser.Config {
int identifierMaxLength();
Casing quotedCasing();
Casing unquotedCasing();
}
and replace all of the parameters of SqlParser’s constructor with one Config
parameter.
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