From d964c2be59a73e6b21ce1a8031fe913588bddf66 Mon Sep 17 00:00:00 2001
From: Stefan Majewsky <majewsky@gmx.net>
Date: Thu, 16 Apr 2026 21:18:04 +0200
Subject: add Store.Update()

---
 query.go | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 53 insertions(+), 1 deletion(-)

(limited to 'query.go')

diff --git a/query.go b/query.go
index 88c2987..41d61c7 100644
--- a/query.go
+++ b/query.go
@@ -105,7 +105,59 @@ func (s Store[R]) Insert(db Handle, records ...R) (returnedRecords []R, returned
 	return records, nil
 }
 
-// TODO: Store.Update
+// Update executes an SQL UPDATE statement for each of the provided records, updating all non-primary-key columns with the values in the records.
+// Returns [MissingRecordError] if any of the records does not exist in the database, that is, if for any of the records, the database contains no row with the same primary key values.
+//
+// Returns an error if [NewStore] was called without the [TableNameIs] or [PrimaryKeyIs] options, which are both required to generate a query for this method.
+func (s Store[R]) Update(db Handle, records ...R) (returnedError error) {
+	if s.plan.Update.Query == "" {
+		return errors.New("cannot execute Update() because query could not be autogenerated")
+	}
+
+	var (
+		argumentIndexes = s.plan.Update.ArgumentIndexes
+		argumentSlots   = make([]any, len(argumentIndexes))
+	)
+
+	var stmt *sql.Stmt
+	if len(records) >= PrepareThreshold {
+		var err error
+		stmt, err = db.Prepare(s.plan.Update.Query)
+		if err != nil {
+			return fmt.Errorf("during Prepare(): %w", err)
+		}
+		defer func() {
+			returnedError = mergeCloseError("Stmt", returnedError, stmt.Close())
+		}()
+	}
+
+	for idx, r := range records {
+		v := reflect.ValueOf(&r).Elem()
+		for idx, index := range argumentIndexes {
+			argumentSlots[idx] = v.FieldByIndex(index).Addr().Interface()
+		}
+		var (
+			result sql.Result
+			err    error
+		)
+		if stmt == nil {
+			result, err = db.Exec(s.plan.Update.Query, argumentSlots...)
+		} else {
+			result, err = stmt.Exec(argumentSlots...)
+		}
+		if err != nil {
+			return fmt.Errorf("during Exec() for record with idx = %d: %w", idx, err)
+		}
+		rowsAffected, err := result.RowsAffected()
+		if err != nil {
+			return fmt.Errorf("during RowsAffected() for record with idx = %d: %w", idx, err)
+		}
+		if rowsAffected == 0 {
+			return MissingRecordError[R]{r, s.plan}
+		}
+	}
+	return nil
+}
 
 // Delete executes an SQL DELETE statement for each of the provided records, using their primary keys to locate the respective table rows.
 //
-- 
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