Generic dialect support. (MySQL and Postgres)

dialects.go

@@ -0,0 +1,97 @@
+package jet
+
+import (
+	"github.com/pkg/errors"
+	"strconv"
+)
+
+var (
+	PostgreSQL = newPostgresDialect()
+	MySql      = newMySQLDialect()
+)
+
+func newPostgresDialect() Dialect {
+	postgresDialect := newDialect("PostgreSQL", "postgres")
+
+	postgresDialect.OperatorOverrides["IS DISTINCT FROM"] = postgresIS_DISTINCT_FROM
+	postgresDialect.CastOverride = postgresCAST
+	postgresDialect.AliasQuoteChar = '"'
+	postgresDialect.IdentifierQuoteChar = '"'
+	postgresDialect.ArgumentPlaceholder = func(ord int) string {
+		return "$" + strconv.Itoa(ord)
+	}
+
+	return postgresDialect
+}
+
+func newMySQLDialect() Dialect {
+	mySQLDialect := newDialect("MySQL", "mysql")
+
+	mySQLDialect.AliasQuoteChar = '"'
+	mySQLDialect.IdentifierQuoteChar = '"'
+	mySQLDialect.ArgumentPlaceholder = func(int) string {
+		return "?"
+	}
+
+	return mySQLDialect
+}
+
+type Dialect struct {
+	Name                string
+	PackageName         string
+	OperatorOverrides   map[string]serializeOverride
+	CastOverride        castOverride
+	AliasQuoteChar      byte
+	IdentifierQuoteChar byte
+	ArgumentPlaceholder queryPlaceholderFunc
+}
+
+func (d *Dialect) serializeOverride(operator string) serializeOverride {
+	return d.OperatorOverrides[operator]
+}
+
+type queryPlaceholderFunc func(ord int) string
+
+func newDialect(name, packageName string) Dialect {
+	newDialect := Dialect{
+		Name:        name,
+		PackageName: packageName,
+	}
+	newDialect.OperatorOverrides = make(map[string]serializeOverride)
+
+	return newDialect
+}
+
+func postgresIS_DISTINCT_FROM(expressions ...Expression) serializeFunc {
+	return func(statement statementType, out *sqlBuilder, options ...serializeOption) error {
+		if len(expressions) != 2 {
+			return errors.New("Invalid number of expressions for operator")
+		}
+		if err := expressions[0].serialize(statement, out); err != nil {
+			return err
+		}
+
+		out.writeString("IS DISTINCT FROM")
+
+		if err := expressions[1].serialize(statement, out); err != nil {
+			return err
+		}
+
+		return nil
+	}
+}
+
+func postgresCAST(expression Expression, castType string) serializeFunc {
+	return func(statement statementType, out *sqlBuilder, options ...serializeOption) error {
+		if err := expression.serialize(statement, out, options...); err != nil {
+			return err
+		}
+		out.writeString("::" + castType)
+		return nil
+	}
+}
+
+type serializeFunc func(statement statementType, out *sqlBuilder, options ...serializeOption) error
+type serializeOverride func(expressions ...Expression) serializeFunc
+
+type castOverride func(expression Expression, castType string) serializeFunc