1 files changed, 70 insertions, 0 deletions
diff --git a/dialect.go b/dialect.go
new file mode 100644
index 0000000..f29a34a
--- /dev/null
+++ b/dialect.go
@@ -0,0 +1,70 @@
+// SPDX-FileCopyrightText: 2026 Stefan Majewsky <majewsky@gmx.net>
+// SPDX-License-Identifier: Apache-2.0
+
+package oblast
+
+import (
+	"strconv"
+	"strings"
+)
+
+// Dialect accounts for differences between different SQL dialects
+// that are relevant to query generation within Oblast.
+//
+// # Compatibility notice
+//
+// This interface may be extended, even within minor versions, when doing so is
+// required to add support for new DB dialects that differ from previously
+// supported dialects in unexpected ways.
+type Dialect interface {
+	// Placeholder returns the placeholder for the i-th query argument.
+	// Most dialects use "?", but e.g. PostgreSQL uses "$1", "$2" and so on.
+	Placeholder(i int) string
+
+	// QuoteIdentifier wraps the name of a column or table in quotes,
+	// in order to avoid the name from being interpreted as a keyword.
+	QuoteIdentifier(name string) string
+
+	// UsesLastInsertID returns whether values for auto-generated columns are
+	// collected from LastInsertID(). If false, the INSERT query must instead
+	// yield a result row containing the values.
+	UsesLastInsertID() bool
+
+	// InsertSuffixForAutoColumns is appended to `INSERT (...) VALUES (...)`
+	// statements to collect values for auto-filled columns.
+	//
+	// If UsesLastInsertID is true, this is usually not needed and the empty
+	// string can be returned.
+	InsertSuffixForAutoColumns(columns []string) string
+}
+
+// PostgresDialect is the dialect of PostgreSQL databases.
+func PostgresDialect() Dialect {
+	return postgresDialect{}
+}
+
+type postgresDialect struct{}
+
+func (postgresDialect) Placeholder(i int) string           { return "$" + strconv.Itoa(i) }
+func (postgresDialect) QuoteIdentifier(name string) string { return `"` + name + `"` }
+func (postgresDialect) UsesLastInsertID() bool             { return false }
+
+func (p postgresDialect) InsertSuffixForAutoColumns(columns []string) string {
+	quotedColumns := make([]string, len(columns))
+	for idx, name := range columns {
+		quotedColumns[idx] = p.QuoteIdentifier(name)
+	}
+	return ` RETURNING ` + strings.Join(quotedColumns, ", ")
+}
+
+// SqliteDialect is the dialect of SQLite databases.
+func SqliteDialect() Dialect {
+	return sqliteDialect{}
+}
+
+type sqliteDialect struct{}
+
+func (sqliteDialect) Placeholder(_ int) string                           { return "?" }
+func (sqliteDialect) QuoteIdentifier(name string) string                 { return `"` + name + `"` }
+func (sqliteDialect) UsesLastInsertID() bool                             { return true }
+func (sqliteDialect) InsertSuffixForAutoColumns(columns []string) string { return "" }