codegen: Correctly generate CopyFrom columns for single-column copyfroms

internal/codegen/golang/query.go

@@ -12,6 +12,7 @@ type QueryValue struct {
 	Emit        bool
 	EmitPointer bool
 	Name        string
+	DBName      string // The name of the field in the database. Only set if Struct==nil.
 	Struct      *Struct
 	Typ         string
 	SQLDriver   SQLDriver
@@ -116,7 +117,7 @@ func (v QueryValue) Params() string {
 
 func (v QueryValue) ColumnNames() string {
 	if v.Struct == nil {
-		return fmt.Sprintf("[]string{%q}", v.Name)
+		return fmt.Sprintf("[]string{%q}", v.DBName)
 	}
 	escapedNames := make([]string, len(v.Struct.Fields))
 	for i, f := range v.Struct.Fields {

internal/codegen/golang/result.go

@@ -166,6 +166,7 @@ func buildQueries(req *plugin.CodeGenRequest, structs []Struct) ([]Query, error)
 			p := query.Params[0]
 			gq.Arg = QueryValue{
 				Name:      paramName(p),
+				DBName:    p.Column.GetName(),
 				Typ:       goType(req, p.Column),
 				SQLDriver: sqlpkg,
 			}
@@ -198,6 +199,7 @@ func buildQueries(req *plugin.CodeGenRequest, structs []Struct) ([]Query, error)
 			}
 			gq.Ret = QueryValue{
 				Name:      name,
+				DBName:    name,
 				Typ:       goType(req, c),
 				SQLDriver: sqlpkg,
 			}

internal/endtoend/testdata/copyfrom_singlecolumn/postgresql/pgx/v4/query.sql

@@ -0,0 +1,6 @@
+CREATE TABLE authors (
+    author_id SERIAL PRIMARY KEY
+);
+
+-- name: CreateAuthors :copyfrom
+INSERT INTO authors (author_id) VALUES ($1);

internal/endtoend/testdata/copyfrom_singlecolumn/postgresql/pgx/v4/sqlc.json

@@ -0,0 +1,14 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "engine": "postgresql",
+      "sql_package": "pgx/v4",
+      "name": "querytest",
+      "schema": "query.sql",
+      "queries": "query.sql",
+      "emit_interface": true
+    }
+  ]
+}

internal/endtoend/testdata/copyfrom_singlecolumn/postgresql/pgx/v5/query.sql

@@ -0,0 +1,6 @@
+CREATE TABLE authors (
+    author_id SERIAL PRIMARY KEY
+);
+
+-- name: CreateAuthors :copyfrom
+INSERT INTO authors (author_id) VALUES ($1);

internal/endtoend/testdata/copyfrom_singlecolumn/postgresql/pgx/v5/sqlc.json

@@ -0,0 +1,14 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "engine": "postgresql",
+      "sql_package": "pgx/v5",
+      "name": "querytest",
+      "schema": "query.sql",
+      "queries": "query.sql",
+      "emit_interface": true
+    }
+  ]
+}