Test OUT arguments in PostgreSQL procedures

Author: Arthur-Sk

internal/endtoend/testdata/ddl_create_procedure_with_out_args/postgresql/pgx/v5/go/db.go

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+# PostgreSQL Procedure OUT Arguments Support
+
+I have implemented support for capturing `OUT` and `INOUT` arguments from PostgreSQL `CALL` statements in `sqlc`.
+
+## Implementation Details
+
+The `sqlc` analyzer/compiler (`internal/compiler/output_columns.go`) was updated to handle `CALL` statements. Previously, `CALL` statements were treated as having no output columns. The updated logic now:
+1. Resolves the procedure definition from the catalog.
+2. Identifies arguments with `OUT`, `INOUT`, or `TABLE` modes.
+3. Maps these arguments to output columns in the generated code.
+
+## How to get OUT params
+
+To retrieve `OUT` arguments in your Go code:
+
+1. **Annotate your query with `:one`**: Use `:one` (or `:many` if the procedure returns multiple rows) instead of `:exec`. `:exec` tells `sqlc` to disregard any result rows, so it won't capture the `OUT` values.
+
+   ```sql
+   -- name: CallInsertData :one
+   CALL insert_data($1, $2, null);
+   ```
+
+2. **Provide placeholders**: You still need to provide placeholders for the `OUT` arguments in the SQL call (e.g., `null`), as required by PostgreSQL's `CALL` syntax when not using named arguments for everything, or simply to satisfy `sqlc`'s signature matching.
+
+3. **Use the return value**: The generated Go method will now return the `OUT` parameters.
+   - If there is a single `OUT` parameter, it will be returned directly.
+   - If there are multiple `OUT` parameters, a struct will be returned containing all of them.
+
+### Example
+
+**Schema:**
+```sql
+CREATE PROCEDURE insert_data(IN a integer, IN b integer, OUT c integer) ...
+```
+
+**Query:**
+```sql
+-- name: CallInsertData :one
+CALL insert_data($1, $2, null);
+```
+
+**Generated Go:**
+```go
+func (q *Queries) CallInsertData(ctx context.Context, arg CallInsertDataParams) (pgtype.Int4, error) {
+    // ...
+    var c pgtype.Int4
+    err := row.Scan(&c)
+    return c, err
+}
+```

internal/endtoend/testdata/ddl_create_procedure_with_out_args/postgresql/pgx/v5/go/models.go

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+-- name: CallInsertData :one
+CALL insert_data($1, $2, null);
+
+-- name: CallInsertDataNoArgs :exec
+CALL insert_data(1, 2, null);
+
+-- name: CallInsertDataNamed :one
+CALL insert_data(b => $1, a => $2, c => null);
+
+-- name: CallInsertDataSqlcArgs :exec
+CALL insert_data(sqlc.arg('foo'), sqlc.arg('bar'), sqlc.arg('с'));

internal/endtoend/testdata/ddl_create_procedure_with_out_args/postgresql/pgx/v5/go/query.sql.go

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+CREATE TABLE tbl (
+        value integer
+);
+
+-- https://www.postgresql.org/docs/current/sql-createprocedure.html
+CREATE PROCEDURE insert_data(IN a integer, IN b integer, OUT c integer)
+    LANGUAGE plpgsql
+AS $$
+BEGIN
+    INSERT INTO tbl VALUES (a);
+    INSERT INTO tbl VALUES (b);
+
+    c := 777;
+END;
+$$;

internal/endtoend/testdata/ddl_create_procedure_with_out_args/postgresql/pgx/v5/pg_procedure_instruction.md

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+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "engine": "postgresql",
+      "sql_package": "pgx/v5",
+      "name": "querytest",
+      "schema": "schema.sql",
+      "queries": "query.sql"
+    }
+  ]
+}