feat(python/sedonadb): Ensure dataframes have meaningful default alias

[paleolimbot]

This PR ensures all dataframes when created have a default alias that is probably unique and mostly meaningful (e.g., the filename being read). This ensures that joins don't require manual aliasing in most cases.

Motivating use case:

import sedona.db

sd = sedona.db.connect()

pts = sd.read_parquet(
    "https://github.com/geoarrow/geoarrow-data/releases/download/v0.2.0/ns-water_water-point.parquet"
)
ply = sd.read_parquet(
    "https://github.com/geoarrow/geoarrow-data/releases/download/v0.2.0/ns-water_water-poly.parquet"
)
pts.join(ply, on=sd.funcs.st_intersects(pts.geometry, ply.geometry)).select(
    pt_hid=pts.HID, pl_hid=ply.HID, geometry=pts.geometry
).show(5)
# ┌────────────────────────────────┬────────────────────────────────┬────────────────────────────────┐
# │             pt_hid             ┆             pl_hid             ┆            geometry            │
# │              utf8              ┆              utf8              ┆            geometry            │
# ╞════════════════════════════════╪════════════════════════════════╪════════════════════════════════╡
# │ FC9A29123BEF4A6588A2FD777B81A… ┆ 63E9CC5AE7144EEABEBEC2C95C91F… ┆ POINT Z(258498.62729999982 48… │
# ├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
# │ 28E47E22D71549ED91472AD59A9D8… ┆ 63E9CC5AE7144EEABEBEC2C95C91F… ┆ POINT Z(258498.32830000017 48… │
# ├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
# │ B10B26FA32FB4438925D86CD612BA… ┆ 63E9CC5AE7144EEABEBEC2C95C91F… ┆ POINT Z(258502.0273000002 481… │
# ├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
# │ 6ACD71128B6B492C8177B11A5C2D2… ┆ 63E9CC5AE7144EEABEBEC2C95C91F… ┆ POINT Z(258498.92729999963 48… │
# ├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
# │ 0A4BE2AB03D8459B8279FCC4BDE55… ┆ 63E9CC5AE7144EEABEBEC2C95C91F… ┆ POINT Z(258526.62729999982 48… │
# └────────────────────────────────┴────────────────────────────────┴────────────────────────────────┘

A downside here is that the explain plans get more verbose because they always print out the qualifier.

Closes #926.

[Copilot]

Pull request overview

This PR adds automatic, meaningful default aliases to Python DataFrames at creation time (especially for file-based reads), reducing ambiguous column reference errors in joins without requiring users to manually call .alias() in common cases.

Changes:

• Add _ensure_aliased() + default alias generation to automatically qualify DataFrame columns on creation.
• Apply default aliasing to Context.read_parquet(), Context.read_pyogrio(), Context.read_format(), and Context.sql().
• Add/adjust tests to assert alias behavior and relax a brittle explain-plan output assertion.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
python/sedonadb/python/sedonadb/dataframe.py	Introduces _ensure_aliased() and default-alias generation for newly created DataFrames.
python/sedonadb/python/sedonadb/context.py	Applies automatic aliasing to read helpers and sql().
python/sedonadb/src/dataframe.rs	Special-cases aliasing for EXPLAIN logical plans to keep sd.sql("EXPLAIN ...") executable.
python/sedonadb/tests/test_dataframe.py	Updates tests around DataFrame creation from DataFrame and relaxes a brittle explain assertion.
python/sedonadb/tests/test_context.py	Removes the old test_read_parquet (now covered under io tests).
python/sedonadb/tests/io/test_parquet.py	Adds read_parquet alias assertions and keeps existing parquet behavior checks.
python/sedonadb/tests/io/test_pyogrio.py	Adds an alias assertion when reading a path via pyogrio.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

[paleolimbot]

@jiayuasu Do you have bandwidth to review this one since it's mostly for joins?

[jiayuasu]

Two things give me pause about this mechanism:

1. It doesn't actually solve self-joins. Because the alias is baked from
   the source object at create time, a self-join gets the same qualifier on
   both sides. I tried the predicate path from your example:

  df = sd.create_data_frame(...).alias("foo_deadbeef")   # one default
  alias
  df.join(df, on=df["k"] == df["k"])

2. The id()-based suffix is non-deterministic. the qualifier changes every run

[paleolimbot]

Got it...we can manually alias and/or add spatial join helpers later