How to escape table names in SqlAlchemy

Question

I'm working on a SQLAlchemy dialect for Apache Drill and I've run into an issue that I can't quite seem to figure out.

The basic problem is that SQLAlchemy is generating a query like the one below:

SELECT `field1`, `field2`
FROM dfs.test.data.csv LIMIT 100

which fails because data.csv needs backticks around it as shown below:

SELECT `field1`, `field2`
FROM dfs.test.`data.csv` LIMIT 100

I've defined the various visit_() functions in the dialect's compiler but these seem to have no effect.

Manofwar

Answer 1

This took some time to figure out, and I thought I'd post the result so that if anyone else runs into this issue, they'll have a point of reference as to how to solve it.

Here is the final working code:

https://github.com/JohnOmernik/sqlalchemy-drill/blob/master/sqlalchemy_drill/base.py

Here is what ultimately solved the issue:

    def __init__(self, dialect):
        super(DrillIdentifierPreparer, self).__init__(dialect, initial_quote='`', final_quote='`')

    def format_drill_table(self, schema, isFile=True):
        formatted_schema = ""

        num_dots = schema.count(".")
        schema = schema.replace('`', '')

        # For a file, the last section will be the file extension
        schema_parts = schema.split('.')

        if isFile and num_dots == 3:
            # Case for File + Workspace
            plugin = schema_parts[0]
            workspace = schema_parts[1]
            table = schema_parts[2] + "." + schema_parts[3]
            formatted_schema = plugin + ".`" + workspace + "`.`" + table + "`"
        elif isFile and num_dots == 2:
            # Case for file and no workspace
            plugin = schema_parts[0]
            formatted_schema = plugin + "." + schema_parts[1] + ".`" + schema_parts[2] + "`"
        else:
            # Case for non-file plugins or incomplete schema parts
            for part in schema_parts:
                quoted_part = "`" + part + "`"
                if len(formatted_schema) > 0:
                    formatted_schema += "." + quoted_part
                else:
                    formatted_schema = quoted_part

        return formatted_schema

Manofwar