DuckDB POSITIONAL JOIN syntax

[dylanscott]

DuckDB supports a unique positional join type which matches up rows of equal length tables, documented here. Currently sqlglot's duckdb dialect does not recognize this syntax and interprets it as an alias for a normal join.

Here's a minimal repro, using the example from the documentation:

from sqlglot import parse_one

parsed = parse_one("""
SELECT df1.*, df2.*
FROM df1
POSITIONAL JOIN df2;
""", dialect="duckdb")

print(f"""
{parsed!r}
--------------------
{parsed.sql(dialect="duckdb", pretty=True)}
""")

Which prints

Select(
  expressions=[
    Column(
      this=Star(),
      table=Identifier(this=df1, quoted=False)),
    Column(
      this=Star(),
      table=Identifier(this=df2, quoted=False))],
  from=From(
    this=Table(
      this=Identifier(this=df1, quoted=False),
      alias=TableAlias(
        this=Identifier(this=POSITIONAL, quoted=False)))),
  joins=[
    Join(
      this=Table(
        this=Identifier(this=df2, quoted=False)))])
--------------------
SELECT
  df1.*,
  df2.*
FROM df1 AS POSITIONAL, df2