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import itertools
from sqlglot import alias, exp
from sqlglot.helper import csv_reader
from sqlglot.optimizer.scope import traverse_scope
def qualify_tables(expression, db=None, catalog=None, schema=None):
"""
Rewrite sqlglot AST to have fully qualified tables.
Example:
>>> import sqlglot
>>> expression = sqlglot.parse_one("SELECT 1 FROM tbl")
>>> qualify_tables(expression, db="db").sql()
'SELECT 1 FROM db.tbl AS tbl'
Args:
expression (sqlglot.Expression): expression to qualify
db (str): Database name
catalog (str): Catalog name
schema: A schema to populate
Returns:
sqlglot.Expression: qualified expression
"""
sequence = itertools.count()
for scope in traverse_scope(expression):
for derived_table in scope.ctes + scope.derived_tables:
if not derived_table.args.get("alias"):
alias_ = f"_q_{next(sequence)}"
derived_table.set("alias", exp.TableAlias(this=exp.to_identifier(alias_)))
scope.rename_source(None, alias_)
for source in scope.sources.values():
if isinstance(source, exp.Table):
identifier = isinstance(source.this, exp.Identifier)
if identifier:
if not source.args.get("db"):
source.set("db", exp.to_identifier(db))
if not source.args.get("catalog"):
source.set("catalog", exp.to_identifier(catalog))
if not source.alias:
source = source.replace(
alias(
source.copy(),
source.this if identifier else f"_q_{next(sequence)}",
table=True,
)
)
if schema and isinstance(source.this, exp.ReadCSV):
with csv_reader(source.this) as reader:
header = next(reader)
columns = next(reader)
schema.add_table(
source, {k: type(v).__name__ for k, v in zip(header, columns)}
)
return expression
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