bug(flink): memtables with nested data do not compile/execute correctly on Flink backend

[chloeh13q]

What happened?

ibis.memtable() expressions do not compile/execute correctly on Flink backend.

Examples:
1.

t = ibis.memtable({"arr": [[], ["a"], ["a", "b"]]})
con.execute(t)

compiles into

SELECT
  `arr`
FROM (VALUES
  (CAST(ARRAY[] AS ARRAY<STRING>)),
  (ARRAY['a']),
  (ARRAY['a', 'b'])) AS `ibis_pandas_memtable_odkwlixgsfdmtmxfcd6ezswwpe`(`arr`)

which throws

Caused by: org.apache.calcite.runtime.CalciteContextException: From line 4, column 9 to line 4, column 15: Require at least 1 argument

jobs = ibis.memtable(
    {
        "steps": [
            [
                {"status": "success"},
                {"status": "success"},
                {"status": None},
                {"status": "failure"},
            ],
            [
                {"status": None},
                {"status": "success"},
            ],
        ]
    },
    schema=dict(steps="array<struct<status: string>>"),
)
con.execute(jobs)

compiles into

SELECT
  `steps`
FROM (VALUES
  (ARRAY[STRUCT('success' AS `status`), STRUCT('success' AS `status`), STRUCT(CAST(NULL AS STRING) AS `status`), STRUCT('failure' AS `status`)]),
  (ARRAY[STRUCT(CAST(NULL AS STRING) AS `status`), STRUCT('success' AS `status`)])) AS `ibis_pandas_memtable_gnydymxcijastata6eh4tiuwhq`(`steps`)

which throws

Caused by: org.apache.calcite.sql.parser.SqlParseException: Encountered "AS" at line 4, column 27.

What version of ibis are you using?

8.0

What backend(s) are you using, if any?

Flink

Relevant log output

No response

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