Parsing fails if -- comment is included inside arguments of function call (but succeeds with /* comment */)

[milesrichardson]

It's possible this is a non-issue. I'm not sure if this (the failing query) is valid SQL or not. Perhaps it's valid SQL when sent in the query, but once it gets normalized (newlines removed) it's not valid SQL.

✅ This query succeeds (no comment):

curl -i \
    -H "Content-Type: application/json" \
https://splitgraph-testing-nomad.seafowl.cloud/q -d@-<<EOF
{"query": "WITH t (
          c_int16_smallint,
          c_int32_int
        ) AS (
          VALUES(
            42::SMALLINT,
            99::INT
          )
        ) SELECT * FROM t;
"}
EOF

# Returns:
HTTP/2 200 
content-type: application/octet-stream
vary: Content-Type, Origin, X-Seafowl-Query
content-length: 41
date: Thu, 27 Apr 2023 00:15:36 GMT
server: Fly/199ec4d3 (2023-04-25)
via: 2 fly.io
fly-request-id: 01GZ011GHJERYT9V5102YEE0XV-lhr

{"c_int16_smallint":42,"c_int32_int":99}

❌ This query fails (note the comment -- Some comment inside the VALUES() function (the result is the same even if the comment starts at the beginning of the line):

curl -i \
    -H "Content-Type: application/json" \
https://splitgraph-testing-nomad.seafowl.cloud/q -d@-<<EOF
{"query": "WITH t (
          c_int16_smallint,
          c_int32_int
        ) AS (
          VALUES(
		  -- Some comment
            42::SMALLINT,
            99::INT
          )
        ) SELECT * FROM t;
"}
EOF

# Returns
HTTP/2 400 
vary: Content-Type, Origin, X-Seafowl-Query
content-length: 61
date: Thu, 27 Apr 2023 00:18:44 GMT
server: Fly/199ec4d3 (2023-04-25)
via: 2 fly.io
fly-request-id: 01GZ0177Q78W55HQ4V9FT7YGR7-lhr

SQL error: ParserError("Expected an expression:, found: EOF")

✅ This query succeeds (note the /* Some comment */:

curl -i \
    -H "Content-Type: application/json" \
https://splitgraph-testing-nomad.seafowl.cloud/q -d@-<<EOF
{"query": "WITH t (
          c_int16_smallint,
          c_int32_int
        ) AS (
          VALUES(
		  /* Some comment */
            42::SMALLINT,
            99::INT
          )
        ) SELECT * FROM t;
"}
EOF


# Returns
HTTP/2 200 
content-type: application/octet-stream
vary: Content-Type, Origin, X-Seafowl-Query
content-length: 41
date: Thu, 27 Apr 2023 00:23:59 GMT
server: Fly/199ec4d3 (2023-04-25)
via: 2 fly.io
fly-request-id: 01GZ01GVS3SGZYZFHMKB2136TC-lhr

{"c_int16_smallint":42,"c_int32_int":99}

[gruuya]

The reason for this is actually external to Seafowl: the curl's -d option strips the control characters (CR, LF) from the query. Hence, the raw query received by Seafowl in example #2 is

WITH t (          c_int16_smallint,          c_int32_int        ) AS (          VALUES(                  -- Some comment            42::SMALLINT,            99::INT          )        ) SELECT * FROM t;

Note that the part of the query after the comment has turned into a comment, which leads to the parsing error. The /* Some comment */ variant has a closing delimiter, so it doesn't interfere with the parsing.

This shouldn't be an issue with other clients. For instance in Python:

In [99]: query = """WITH t (
    ...:           c_int16_smallint,
    ...:           c_int32_int
    ...:         ) AS (
    ...:           VALUES(
    ...:             -- Some comment
    ...:             42::SMALLINT,
    ...:             99::INT
    ...:           )
    ...:         ) SELECT * FROM t;
    ...: """

In [100]: r = requests.post("http://localhost:8080/q", json={"query": query}, headers={"content-type": "application/json"})

In [101]: print(r.text)
{"c_int16_smallint":42,"c_int32_int":99}

whereby the query received by Seafowl has explicit line breaks:

WITH t (\n          c_int16_smallint,\n          c_int32_int\n        ) AS (\n          VALUES(\n            -- Some comment\n            42::SMALLINT,\n            99::INT\n          )\n        ) SELECT * FROM t;\n