DapperLib / DapperLib/Dapper

Sql with `in` clause fails with PostgreSQL

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C#
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Description

Following fails

var result = con.Query<Drivers>("select first_name, last_name from drivers where first_name in @Ids", new { Ids = new string[] {"Sandeep", "Sam"}});

with exception
Unhandled Exception: Npgsql.PostgresException: 42601: syntax error at or near "$1" at Npgsql.NpgsqlConnector.<>c__DisplayClass161_0.<<ReadMessage>g__ReadMessageLong|0>d.MoveNext() --- End of stack trace from previous location where exception was thrown --- at Npgsql.NpgsqlConnector.<>c__DisplayClass161_0.<<ReadMessage>g__ReadMessageLong|0>d.MoveNext() in C:\projects\npgsql\src\Npgsql\NpgsqlConnector.cs:line 1032

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Research direction

Reproduce the shown Dapper query against PostgreSQL and start by tracing how the IN @Ids parameter is handled before Npgsql receives it. Inspect the parameter-expansion entry point and existing query tests, then add coverage showing the query succeeds with the provided string array.

Written by the indexing model from the issue text.

Assessment

Tech stack
csharp, postgresql
Domain
backend, database
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
45/100

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