Running sql scripts from graphical clients sends all sql statements as a single query string

[kishaningithub]

Context

When i run sql scripts through vscode sql tools. The received query string in SimpleQueryFn is of the form

select * from employee limit 10;\nselect count(*) from student;

What i tried

In the SimpleQueryFn implementation that i wrote, i tried splitting the sql with ; character and running it separately and this results in the error columns have already been defined

What i expect

I expect psql wire to do the split and send queries one by one inside the SimpleQueryFn

What are your thoughts?

[jeroenrinzema]

Hi @kishaningithub, thanks for reporting this! We have to update the writer to allow for multiple column definitions to be returned. Looking at the PostgreSQL documentation it should be possible to send multiple row definitions after a single query message. I will update the writer and include a check to make sure that the previous definition has been marked as complete.

[jeroenrinzema]

@kishaningithub would you be able to include some debug logs of the psql server?

[kishaningithub]

Below are the logs (took this by pointing my psql server to the PR)

{"level":"debug","timestamp":"2022-11-10T21:31:05.303184+05:30","caller":"[email protected]/wire.go:126","msg":"serving a new client connection"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.305053+05:30","caller":"[email protected]/wire.go:137","msg":"handshake successfull, validating authentication"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.305105+05:30","caller":"[email protected]/handshake.go:74","msg":"reading client parameters"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.305118+05:30","caller":"[email protected]/handshake.go:92","msg":"client parameter","key":"user","value":"asfsdf"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.30513+05:30","caller":"[email protected]/handshake.go:92","msg":"client parameter","key":"database","value":"asfsf"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.305145+05:30","caller":"[email protected]/handshake.go:92","msg":"client parameter","key":"client_encoding","value":"UTF8"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.305154+05:30","caller":"[email protected]/auth.go:33","msg":"authenticating client connection"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.311113+05:30","caller":"[email protected]/wire.go:150","msg":"connection authenticated, writing server parameters"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.311174+05:30","caller":"[email protected]/handshake.go:108","msg":"writing server parameters"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.311201+05:30","caller":"[email protected]/handshake.go:119","msg":"server parameter","key":"client_encoding","value":"UTF8"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.311267+05:30","caller":"[email protected]/handshake.go:119","msg":"server parameter","key":"is_superuser","value":"off"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.31138+05:30","caller":"[email protected]/handshake.go:119","msg":"server parameter","key":"session_authorization","value":"asfsdf"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.31167+05:30","caller":"[email protected]/handshake.go:119","msg":"server parameter","key":"server_encoding","value":"UTF8"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.311732+05:30","caller":"[email protected]/command.go:39","msg":"ready for query... starting to consume commands"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.312162+05:30","caller":"[email protected]/command.go:67","msg":"incoming command","length":82,"type":"Q"}
{"level":"debug","timestamp":"2022-11-10T21:31:05.312244+05:30","caller":"[email protected]/command.go:220","msg":"incoming simple query","query":"select * from employee limit 10;\nselect count(*) from student;"}

[kishaningithub]

Feel free to ask me if you need anything more

[kishaningithub]

i understood #41 (comment) only now 🤦

I updated the query handler to split using ";" and run statements so that the way it performs operation is

Pseudocode

for query in queries.split(";") 
    run query
    write column metadata
    write rows
    write Complete msg

What happens is for the first query the result is written correctly. From the second query onwards i get the error

The columnWidths property is given an invalid value.

I tried it with several query combinations, it is always only the first query that succeeds

[kishaningithub]

I also have this question (may be it should belong in discussions)

How should a consumer handle parameters array for bulk queries like this?

[jeroenrinzema]

It is currently a bit unclear to me how bulk queries have to be handled within the PostgreSQL wire protocol. It is mentioned within the message flow format document that multiple queries could be send.

Processing of the query string is complete. A separate message is sent to indicate this because the query string might contain multiple SQL commands. (CommandComplete marks the end of processing one SQL command, not the whole string.) ReadyForQuery will always be sent, whether processing terminates successfully or with an error.

It seems that most clients are handling bulk queries differently. Most split the query up front and send two separate queries to the server. I will try to reproduce the issue using the VSCode SQL client and try to reverse engineer how the client is expecting messages to be send back.

I would expect that all parameters for a single bulk query have to be send in one go (ex: SELECT * FROM users WHERE id = $1; SELECT * FROM settings WHERE user_id = $2;). But I will have to confirm this once I managed to reproduce the issue.