mysql: keep REPLACE INTO when generating a :copyfrom LOAD DATA

docs/howto/insert.md

@@ -208,6 +208,10 @@ and use SHOW WARNINGS to check for any problems and roll back if necessary.
 
 Check the [error handling](https://dev.mysql.com/doc/refman/8.0/en/load-data.html#load-data-error-handling) documentation for more information.
 
+Writing the query as `REPLACE INTO` generates `LOAD DATA ... REPLACE INTO TABLE`,
+which overwrites rows that collide on a primary or unique key instead of skipping
+them.
+
 ```sql
 CREATE TABLE foo (a text, b integer, c DATETIME, d DATE);
 

internal/cmd/shim.go

@@ -161,6 +161,7 @@ func pluginQueries(r *compiler.Result) []*plugin.Query {
 			Params:          params,
 			Filename:        q.Metadata.Filename,
 			InsertIntoTable: iit,
+			InsertIsReplace: q.InsertIsReplace(),
 		})
 	}
 	return out

internal/codegen/golang/query.go

@@ -279,6 +279,8 @@ type Query struct {
 	Arg          QueryValue
 	// Used for :copyfrom
 	Table *plugin.Identifier
+	// Used for :copyfrom, true when the query was written as REPLACE INTO
+	InsertIsReplace bool
 }
 
 func (q Query) hasRetType() bool {

internal/codegen/golang/result.go

@@ -218,14 +218,15 @@ func buildQueries(req *plugin.GenerateRequest, options *opts.Options, enums []En
 		}
 
 		gq := Query{
-			Cmd:          query.Cmd,
-			ConstantName: constantName,
-			FieldName:    sdk.LowerTitle(query.Name) + "Stmt",
-			MethodName:   query.Name,
-			SourceName:   query.Filename,
-			SQL:          query.Text,
-			Comments:     comments,
-			Table:        query.InsertIntoTable,
+			Cmd:             query.Cmd,
+			ConstantName:    constantName,
+			FieldName:       sdk.LowerTitle(query.Name) + "Stmt",
+			MethodName:      query.Name,
+			SourceName:      query.Filename,
+			SQL:             query.Text,
+			Comments:        comments,
+			Table:           query.InsertIntoTable,
+			InsertIsReplace: query.InsertIsReplace,
 		}
 		sqlpkg := parseDriver(options.SqlPackage)
 

internal/codegen/golang/templates/go-sql-driver-mysql/copyfromCopy.tmpl

@@ -25,9 +25,16 @@ func convertRowsFor{{.MethodName}}(w *io.PipeWriter, {{.Arg.SlicePair}}) {
 {{end -}}
 // {{.MethodName}} uses MySQL's LOAD DATA LOCAL INFILE and is not atomic.
 //
+{{if .InsertIsReplace -}}
+// Errors are treated as warnings and insertion will continue, even without an
+// error for some cases.  Rows that collide on a primary or unique key replace
+// the existing row.  Use this in a transaction and use SHOW WARNINGS to check
+// for any problems and roll back if you want to.
+{{else -}}
 // Errors and duplicate keys are treated as warnings and insertion will
 // continue, even without an error for some cases.  Use this in a transaction
 // and use SHOW WARNINGS to check for any problems and roll back if you want to.
+{{end -}}
 //
 // Check the documentation for more information:
 // https://dev.mysql.com/doc/refman/8.0/en/load-data.html#load-data-error-handling
@@ -40,7 +47,7 @@ func (q *Queries) {{.MethodName}}(ctx context.Context{{if $.EmitMethodsWithDBArg
 	go convertRowsFor{{.MethodName}}(pw, {{.Arg.Name}})
 	// The string interpolation is necessary because LOAD DATA INFILE requires
 	// the file name to be given as a literal string.
-	result, err := {{if (not $.EmitMethodsWithDBArgument)}}q.{{end}}db.ExecContext(ctx, fmt.Sprintf("LOAD DATA LOCAL INFILE '%s' INTO TABLE {{.TableIdentifierForMySQL}} %s ({{range $index, $name := .Arg.ColumnNames}}{{if gt $index 0}}, {{end}}{{$name}}{{end}})", "Reader::" + rh, mysqltsv.Escaping))
+	result, err := {{if (not $.EmitMethodsWithDBArgument)}}q.{{end}}db.ExecContext(ctx, fmt.Sprintf("LOAD DATA LOCAL INFILE '%s' {{if .InsertIsReplace}}REPLACE {{end}}INTO TABLE {{.TableIdentifierForMySQL}} %s ({{range $index, $name := .Arg.ColumnNames}}{{if gt $index 0}}, {{end}}{{$name}}{{end}})", "Reader::" + rh, mysqltsv.Escaping))
 	if err != nil {
 		return 0, err
 	}

internal/compiler/query.go

@@ -55,6 +55,17 @@ type Query struct {
 	RawStmt *ast.RawStmt
 }
 
+// InsertIsReplace reports whether the query was written as REPLACE INTO. MySQL
+// renders a :copyfrom for such a query as LOAD DATA ... REPLACE INTO TABLE, so
+// that rows colliding on a key overwrite instead of being skipped.
+func (q *Query) InsertIsReplace() bool {
+	if q.RawStmt == nil {
+		return false
+	}
+	ins, ok := q.RawStmt.Stmt.(*ast.InsertStmt)
+	return ok && ins.IsReplace
+}
+
 type Parameter struct {
 	Number int
 	Column *Column

internal/endtoend/testdata/codegen_json/gen/codegen.json

@@ -66389,7 +66389,8 @@
       ],
       "comments": [],
       "filename": "query.sql",
-      "insert_into_table": null
+      "insert_into_table": null,
+      "insert_is_replace": false
     },
     {
       "text": "SELECT id, name, bio FROM authors\nORDER BY name",
@@ -66478,7 +66479,8 @@
       "params": [],
       "comments": [],
       "filename": "query.sql",
-      "insert_into_table": null
+      "insert_into_table": null,
+      "insert_is_replace": false
     },
     {
       "text": "INSERT INTO authors (\n          name, bio\n) VALUES (\n  $1, $2\n)\nRETURNING id, name, bio",
@@ -66630,7 +66632,8 @@
         "catalog": "",
         "schema": "",
         "name": "authors"
-      }
+      },
+      "insert_is_replace": false
     },
     {
       "text": "DELETE FROM authors\nWHERE id = $1",
@@ -66670,7 +66673,8 @@
       ],
       "comments": [],
       "filename": "query.sql",
-      "insert_into_table": null
+      "insert_into_table": null,
+      "insert_is_replace": false
     }
   ],
   "sqlc_version": "v1.31.1",

internal/endtoend/testdata/copyfrom/mysql/query.sql

@@ -3,3 +3,6 @@ INSERT INTO foo (a, b, c, d) VALUES (?, ?, ?, ?);
 
 -- name: InsertSingleValue :copyfrom
 INSERT INTO foo (a) VALUES (?);
+
+-- name: ReplaceValues :copyfrom
+REPLACE INTO foo (a, b, c, d) VALUES (?, ?, ?, ?);

internal/endtoend/testdata/process_plugin_sqlc_gen_json/gen/codegen.json

@@ -66391,7 +66391,8 @@
       ],
       "comments": [],
       "filename": "query.sql",
-      "insert_into_table": null
+      "insert_into_table": null,
+      "insert_is_replace": false
     },
     {
       "text": "SELECT id, name, bio FROM authors\nORDER BY name",
@@ -66480,7 +66481,8 @@
       "params": [],
       "comments": [],
       "filename": "query.sql",
-      "insert_into_table": null
+      "insert_into_table": null,
+      "insert_is_replace": false
     },
     {
       "text": "INSERT INTO authors (\n          name, bio\n) VALUES (\n  $1, $2\n)\nRETURNING id, name, bio",
@@ -66632,7 +66634,8 @@
         "catalog": "",
         "schema": "",
         "name": "authors"
-      }
+      },
+      "insert_is_replace": false
     },
     {
       "text": "DELETE FROM authors\nWHERE id = $1",
@@ -66672,7 +66675,8 @@
       ],
       "comments": [],
       "filename": "query.sql",
-      "insert_into_table": null
+      "insert_into_table": null,
+      "insert_is_replace": false
     }
   ],
   "sqlc_version": "v1.31.1",

internal/engine/dolphin/convert.go

@@ -492,6 +492,7 @@ func (c *cc) convertInsertStmt(n *pcast.InsertStmt) *ast.InsertStmt {
 		Relation:      rangeVar,
 		Cols:          c.convertColumnNames(n.Columns),
 		ReturningList: &ast.List{},
+		IsReplace:     n.IsReplace,
 	}
 	if ss, ok := c.convert(n.Select).(*ast.SelectStmt); ok {
 		ss.ValuesLists = c.convertLists(n.Lists)

internal/sql/ast/insert_stmt.go

@@ -12,6 +12,7 @@ type InsertStmt struct {
 	WithClause           *WithClause
 	Override             OverridingKind
 	DefaultValues        bool // SQLite-specific: INSERT INTO ... DEFAULT VALUES
+	IsReplace            bool // MySQL-specific: REPLACE INTO ... instead of INSERT INTO ...
 }
 
 func (n *InsertStmt) Pos() int {
@@ -28,7 +29,11 @@ func (n *InsertStmt) Format(buf *TrackedBuffer, d format.Dialect) {
 		buf.WriteString(" ")
 	}
 
-	buf.WriteString("INSERT INTO ")
+	if n.IsReplace {
+		buf.WriteString("REPLACE INTO ")
+	} else {
+		buf.WriteString("INSERT INTO ")
+	}
 	if n.Relation != nil {
 		buf.astFormat(n.Relation, d)
 	}

protos/plugin/codegen.proto

@@ -111,6 +111,7 @@ message Query {
   repeated string comments = 6 [json_name = "comments"];
   string filename = 7 [json_name = "filename"];
   Identifier insert_into_table = 8 [json_name = "insert_into_table"];
+  bool insert_is_replace = 9 [json_name = "insert_is_replace"];
 }
 
 message Parameter {