qb: update, delete and performance improvements

qb/update.go

@@ -0,0 +1,110 @@
+package qb
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+)
+
+// UPDATE reference:
+// http://docs.datastax.com/en/dse/5.1/cql/cql/cql_reference/cql_commands/cqlUpdate.html
+
+import (
+	"time"
+)
+
+type UpdateBuilder struct {
+	table   string
+	using   using
+	columns columns
+	where   where
+	_if     _if
+	exists  bool
+}
+
+// Update returns a new UpdateBuilder with the given table name.
+func Update(table string) *UpdateBuilder {
+	return &UpdateBuilder{
+		table: table,
+	}
+}
+
+func (b *UpdateBuilder) ToCql() (stmt string, names []string, err error) {
+	if b.table == "" {
+		err = errors.New("update statements must specify a table")
+		return
+	}
+	if len(b.columns) == 0 {
+		err = fmt.Errorf("update statements must have at least one SET clause")
+		return
+	}
+	if len(b.where) == 0 {
+		err = fmt.Errorf("update statements must have at least one WHERE clause")
+		return
+	}
+
+	cql := bytes.Buffer{}
+
+	cql.WriteString("UPDATE ")
+	cql.WriteString(b.table)
+	cql.WriteByte(' ')
+
+	b.using.writeCql(&cql)
+
+	cql.WriteString("SET ")
+	for i, c := range b.columns {
+		cql.WriteString(c)
+		cql.WriteString("=?")
+		if i < len(b.columns)-1 {
+			cql.WriteByte(',')
+		}
+	}
+	names = append(names, b.columns...)
+	cql.WriteByte(' ')
+
+	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
+}
+
+// Table sets the table to be updated.
+func (b *UpdateBuilder) Table(table string) *UpdateBuilder {
+	b.table = table
+	return b
+}
+
+func (b *UpdateBuilder) Timestamp(t time.Time) *UpdateBuilder {
+	b.using.timestamp = t
+	return b
+}
+
+func (b *UpdateBuilder) TTL(d time.Duration) *UpdateBuilder {
+	b.using.ttl = d
+	return b
+}
+
+func (b *UpdateBuilder) Set(columns ...string) *UpdateBuilder {
+	b.columns = append(b.columns, columns...)
+	return b
+}
+
+func (b *UpdateBuilder) Where(e ...expr) *UpdateBuilder {
+	b.where = append(b.where, e...)
+	return b
+}
+
+func (b *UpdateBuilder) If(e ...expr) *UpdateBuilder {
+	b._if = append(b._if, e...)
+	return b
+}
+
+func (b *UpdateBuilder) Existing() *UpdateBuilder {
+	b.exists = true
+	return b
+}