bug(backends): unexpected chained join behavior

Chained joins in pandas backend don’t behave as expected, and yield an error.

MWE:

import ibis
import pandas as pd

test_df1 = pd.DataFrame({
    'id': ['1', '1'],
    'value': ['a', 'a']
})

test_df2 = pd.DataFrame({
    'id': ['1', '1'],
    'value': ['z', 'z']
})

test_df3 = pd.DataFrame({
    'id': ['1', '1'],
    'value': ['z1', 'z1']
})

conn = ibis.pandas.connect({'df1': test_df1,
                            'df2': test_df2,
                            'df3': test_df3})

t1 = conn.table('df1')
t2 = conn.table('df2')
t3 = conn.table('df3')

expr1 = t1.join(t2, t1.id == t2.id)
expr2 = t1.join(t2, t1.id == t2.id).join(t3, t1.id == t3.id)

#works
print('\n'+expr1.execute())

#fails
print('\n'+expr2.execute())

Error:

KeyError: PandasTable(name='df1', schema=ibis.Schema {
  id     string
  value  string
}, source=<ibis.backends.pandas.Backend object at 0x7f4edbb87e80>)

Does the pandas backend support chained joins / is there a different syntax required than the docs suggest here -> https://ibis-project.org/docs/3.1.0/ibis-for-sql-programmers/?h=left_join#multiple-joins ?

[cpcloud]

In the meantime you should be able to write

from ibis import _
result = t1.join(t2, t1.id==t2.id).join(t3, _.id==t3.id)

Note the _, it refers to everything to the left of the second join call.

[cpcloud]

Interestingly, this appears to be related to overlapping column names in some way:

Not Working

t1 = ibis.table(dict(id="int64"), name="t1")
t2 = ibis.table(dict(id="int64"), name="t2")
t3 = ibis.table(dict(id="int64"), name="t3")

expr = t1.join(t2, t1.id == t2.id).join(t3, t1.id == t3.id)
ibis.show_sql(expr, dialect="duckdb")

SELECT
  t0.id AS id_x,
  t1.id AS id_y
FROM (
  SELECT
    t2.id AS id
  FROM t1 AS t2
  JOIN t2 AS t3
    ON t2.id = t3.id
) AS t0
JOIN t3 AS t1
  ON t2.id = t1.id

Working

t1 = ibis.table(dict(id1="int64"), name="t1")
t2 = ibis.table(dict(id2="int64"), name="t2")
t3 = ibis.table(dict(id3="int64"), name="t3")

expr = t1.join(t2, t1.id1 == t2.id2).join(t3, t1.id1 == t3.id3)
ibis.show_sql(expr, dialect="duckdb")

SELECT
  t0.id1,
  t1.id2,
  t2.id3
FROM t1 AS t0
JOIN t2 AS t1
  ON t0.id1 = t1.id2
JOIN t3 AS t2
  ON t0.id1 = t2.id3