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column.go
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column.go
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// Modeling of columns
package sqlbuilder
import (
"bytes"
"regexp"
"github.com/dropbox/godropbox/errors"
)
// XXX: Maybe add UIntColumn
// Representation of a table for query generation
type Column interface {
isProjectionInterface
Name() string
// Serialization for use in column lists
SerializeSqlForColumnList(out *bytes.Buffer) error
// Serialization for use in an expression (Clause)
SerializeSql(out *bytes.Buffer) error
// Internal function for tracking table that a column belongs to
// for the purpose of serialization
setTableName(table string) error
}
type NullableColumn bool
const (
Nullable NullableColumn = true
NotNullable NullableColumn = false
)
// A column that can be refer to outside of the projection list
type NonAliasColumn interface {
Column
isOrderByClauseInterface
isExpressionInterface
}
type Collation string
const (
UTF8CaseInsensitive Collation = "utf8_unicode_ci"
UTF8CaseSensitive Collation = "utf8_unicode"
UTF8Binary Collation = "utf8_bin"
)
// Representation of MySQL charsets
type Charset string
const (
UTF8 Charset = "utf8"
)
// The base type for real materialized columns.
type baseColumn struct {
isProjection
isExpression
name string
nullable NullableColumn
table string
}
func (c *baseColumn) Name() string {
return c.name
}
func (c *baseColumn) setTableName(table string) error {
c.table = table
return nil
}
func (c *baseColumn) SerializeSqlForColumnList(out *bytes.Buffer) error {
if c.table != "" {
_ = out.WriteByte('`')
_, _ = out.WriteString(c.table)
_, _ = out.WriteString("`.")
}
_, _ = out.WriteString("`")
_, _ = out.WriteString(c.name)
_ = out.WriteByte('`')
return nil
}
func (c *baseColumn) SerializeSql(out *bytes.Buffer) error {
return c.SerializeSqlForColumnList(out)
}
type bytesColumn struct {
baseColumn
isExpression
}
// Representation of VARBINARY/BLOB columns
// This function will panic if name is not valid
func BytesColumn(name string, nullable NullableColumn) NonAliasColumn {
if !validIdentifierName(name) {
panic("Invalid column name in bytes column")
}
bc := &bytesColumn{}
bc.name = name
bc.nullable = nullable
return bc
}
type stringColumn struct {
baseColumn
isExpression
charset Charset
collation Collation
}
// Representation of VARCHAR/TEXT columns
// This function will panic if name is not valid
func StrColumn(
name string,
charset Charset,
collation Collation,
nullable NullableColumn) NonAliasColumn {
if !validIdentifierName(name) {
panic("Invalid column name in str column")
}
sc := &stringColumn{charset: charset, collation: collation}
sc.name = name
sc.nullable = nullable
return sc
}
type dateTimeColumn struct {
baseColumn
isExpression
}
// Representation of DateTime columns
// This function will panic if name is not valid
func DateTimeColumn(name string, nullable NullableColumn) NonAliasColumn {
if !validIdentifierName(name) {
panic("Invalid column name in datetime column")
}
dc := &dateTimeColumn{}
dc.name = name
dc.nullable = nullable
return dc
}
type integerColumn struct {
baseColumn
isExpression
}
// Representation of any integer column
// This function will panic if name is not valid
func IntColumn(name string, nullable NullableColumn) NonAliasColumn {
if !validIdentifierName(name) {
panic("Invalid column name in int column")
}
ic := &integerColumn{}
ic.name = name
ic.nullable = nullable
return ic
}
type doubleColumn struct {
baseColumn
isExpression
}
// Representation of any double column
// This function will panic if name is not valid
func DoubleColumn(name string, nullable NullableColumn) NonAliasColumn {
if !validIdentifierName(name) {
panic("Invalid column name in int column")
}
ic := &doubleColumn{}
ic.name = name
ic.nullable = nullable
return ic
}
type booleanColumn struct {
baseColumn
isExpression
// XXX: Maybe allow isBoolExpression (for now, not included because
// the deferred lookup equivalent can never be isBoolExpression)
}
// Representation of TINYINT used as a bool
// This function will panic if name is not valid
func BoolColumn(name string, nullable NullableColumn) NonAliasColumn {
if !validIdentifierName(name) {
panic("Invalid column name in bool column")
}
bc := &booleanColumn{}
bc.name = name
bc.nullable = nullable
return bc
}
type aliasColumn struct {
baseColumn
expression Expression
}
func (c *aliasColumn) SerializeSql(out *bytes.Buffer) error {
_ = out.WriteByte('`')
_, _ = out.WriteString(c.name)
_ = out.WriteByte('`')
return nil
}
func (c *aliasColumn) SerializeSqlForColumnList(out *bytes.Buffer) error {
if !validIdentifierName(c.name) {
return errors.Newf(
"Invalid alias name `%s`. Generated sql: %s",
c.name,
out.String())
}
if c.expression == nil {
return errors.Newf(
"Cannot alias a nil expression. Generated sql: %s",
out.String())
}
_ = out.WriteByte('(')
if c.expression == nil {
return errors.Newf("nil alias clause. Generate sql: %s", out.String())
}
if err := c.expression.SerializeSql(out); err != nil {
return err
}
_, _ = out.WriteString(") AS `")
_, _ = out.WriteString(c.name)
_ = out.WriteByte('`')
return nil
}
func (c *aliasColumn) setTableName(table string) error {
return errors.Newf(
"Alias column '%s' should never have setTableName called on it",
c.name)
}
// Representation of aliased clauses (expression AS name)
func Alias(name string, c Expression) Column {
ac := &aliasColumn{}
ac.name = name
ac.expression = c
return ac
}
// This is a strict subset of the actual allowed identifiers
var validIdentifierRegexp = regexp.MustCompile("^[a-zA-Z_]\\w*$")
// Returns true if the given string is suitable as an identifier.
func validIdentifierName(name string) bool {
return validIdentifierRegexp.MatchString(name)
}
// Pseudo Column type returned by table.C(name)
type deferredLookupColumn struct {
isProjection
isExpression
table *Table
colName string
cachedColumn NonAliasColumn
}
func (c *deferredLookupColumn) Name() string {
return c.colName
}
func (c *deferredLookupColumn) SerializeSqlForColumnList(
out *bytes.Buffer) error {
return c.SerializeSql(out)
}
func (c *deferredLookupColumn) SerializeSql(out *bytes.Buffer) error {
if c.cachedColumn != nil {
return c.cachedColumn.SerializeSql(out)
}
col, err := c.table.getColumn(c.colName)
if err != nil {
return err
}
c.cachedColumn = col
return col.SerializeSql(out)
}
func (c *deferredLookupColumn) setTableName(table string) error {
return errors.Newf(
"Lookup column '%s' should never have setTableName called on it",
c.colName)
}