[postgres] Add support for ON CONFLICT clause

postgres/clause.go

@@ -0,0 +1,87 @@
+package postgres
+
+import (
+	"github.com/go-jet/jet/internal/jet"
+)
+
+type clauseReturning struct {
+	Projections []jet.Projection
+}
+
+func (r *clauseReturning) Serialize(statementType jet.StatementType, out *jet.SQLBuilder, options ...jet.SerializeOption) {
+	if len(r.Projections) == 0 {
+		return
+	}
+
+	out.NewLine()
+	out.WriteString("RETURNING")
+	out.IncreaseIdent()
+	out.WriteProjections(statementType, r.Projections)
+}
+
+// ========================================== //
+
+type onConflict interface {
+	ON_CONSTRAINT(name string) conflictTarget
+	WHERE(indexPredicate BoolExpression) conflictTarget
+	DO_NOTHING() InsertStatement
+	DO_UPDATE(action conflictAction) InsertStatement
+}
+
+type conflictTarget interface {
+	DO_NOTHING() InsertStatement
+	DO_UPDATE(action conflictAction) InsertStatement
+}
+
+type onConflictClause struct {
+	insertStatement  InsertStatement
+	constraint       string
+	indexExpressions []jet.ColumnExpression
+	whereClause      jet.ClauseWhere
+	do               jet.Serializer
+}
+
+func (o *onConflictClause) ON_CONSTRAINT(name string) conflictTarget {
+	o.constraint = name
+	return o
+}
+
+func (o *onConflictClause) WHERE(indexPredicate BoolExpression) conflictTarget {
+	o.whereClause.Condition = indexPredicate
+	return o
+}
+
+func (o *onConflictClause) DO_NOTHING() InsertStatement {
+	o.do = jet.Keyword("DO NOTHING")
+	return o.insertStatement
+}
+
+func (o *onConflictClause) DO_UPDATE(action conflictAction) InsertStatement {
+	o.do = action
+	return o.insertStatement
+}
+
+func (o *onConflictClause) Serialize(statementType jet.StatementType, out *jet.SQLBuilder, options ...jet.SerializeOption) {
+	if len(o.indexExpressions) == 0 && o.constraint == "" {
+		return
+	}
+
+	out.NewLine()
+	out.WriteString("ON CONFLICT")
+	if len(o.indexExpressions) > 0 {
+		out.WriteString("(")
+		jet.SerializeColumnExpressionNames(o.indexExpressions, statementType, out, jet.ShortName)
+		out.WriteString(")")
+	}
+
+	if o.constraint != "" {
+		out.WriteString("ON CONSTRAINT")
+		out.WriteString(o.constraint)
+	}
+
+	o.whereClause.Serialize(statementType, out, jet.SkipNewLine, jet.ShortName)
+
+	out.IncreaseIdent(7)
+	jet.Serialize(o.do, statementType, out)
+	out.DecreaseIdent(7)
+}