qb: update, delete and performance improvements

qb/delete.go

@@ -0,0 +1,93 @@
+package qb
+
+// DELETE reference:
+// http://docs.datastax.com/en/dse/5.1/cql/cql/cql_reference/cql_commands/cqlDelete.html
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"time"
+)
+
+type DeleteBuilder struct {
+	table   string
+	columns columns
+	using   using
+	where   where
+	_if     _if
+	exists  bool
+}
+
+// Delete returns a new DeleteBuilder with the given table name.
+func Delete(table string) *DeleteBuilder {
+	return &DeleteBuilder{
+		table: table,
+	}
+}
+
+func (b *DeleteBuilder) ToCql() (stmt string, names []string, err error) {
+	if b.table == "" {
+		err = errors.New("delete statements must specify a table")
+		return
+	}
+	if len(b.where) == 0 {
+		err = fmt.Errorf("delete statements must have at least one WHERE clause")
+		return
+	}
+
+	cql := bytes.Buffer{}
+
+	cql.WriteString("DELETE ")
+	if len(b.columns) > 0 {
+		b.columns.writeCql(&cql)
+		cql.WriteByte(' ')
+	}
+	cql.WriteString("FROM ")
+	cql.WriteString(b.table)
+	cql.WriteByte(' ')
+
+	b.using.writeCql(&cql)
+
+	names = append(names, b.where.writeCql(&cql)...)
+	names = append(names, b._if.writeCql(&cql)...)
+
+	if b.exists {
+		cql.WriteString("IF EXISTS ")
+	}
+
+	stmt = cql.String()
+	return
+}
+
+// From sets the table to be deleted from.
+func (b *DeleteBuilder) From(table string) *DeleteBuilder {
+	b.table = table
+	return b
+}
+
+// Columns adds delete columns to the query.
+func (b *DeleteBuilder) Columns(columns ...string) *DeleteBuilder {
+	b.columns = append(b.columns, columns...)
+	return b
+}
+
+func (b *DeleteBuilder) Timestamp(t time.Time) *DeleteBuilder {
+	b.using.timestamp = t
+	return b
+}
+
+func (b *DeleteBuilder) Where(e ...expr) *DeleteBuilder {
+	b.where = append(b.where, e...)
+	return b
+}
+
+func (b *DeleteBuilder) If(e ...expr) *DeleteBuilder {
+	b._if = append(b._if, e...)
+	return b
+}
+
+func (b *DeleteBuilder) Existing() *DeleteBuilder {
+	b.exists = true
+	return b
+}