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sqlitemeta.go
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package sqlitemeta
import (
"database/sql"
"fmt"
"strings"
)
// A Schema represents a database attached to the current
// database connection.
type Schema struct {
name string
}
// DB returns a Schema with the given name. It does not verify
// that a database with this name actually exists.
func DB(name string) *Schema {
return &Schema{name}
}
// Main is the database that was used to open a database
// connection.
var Main = DB("main")
// Temp is the database that holds temporary tables, indexes
// etc.
var Temp = DB("temp")
var noSchema = &Schema{}
// SchemaNames returns the names of the databases attached to
// the given database connection, sorted alphabetically.
func SchemaNames(db *sql.DB) ([]string, error) {
names, err := queryStrings(db, "SELECT name FROM pragma_database_list ORDER BY name")
if err != nil {
return nil, fmt.Errorf("could not get schema names: %s", err)
}
return names, nil
}
// TableNames returns the names of the tables in the main
// database, sorted alphabetically. Use the Schema.TableNames
// method to query other databases.
func TableNames(db *sql.DB) ([]string, error) {
return noSchema.TableNames(db)
}
// TableNames returns the names of the tables in this Schema,
// sorted alphabetically.
func (s *Schema) TableNames(db *sql.DB) ([]string, error) {
return s.masterTableNames(db, "table")
}
// ViewNames returns the names of the views in the main database,
// sorted alphabetically. Use the Schema.ViewNames method to query
// other databases.
func ViewNames(db *sql.DB) ([]string, error) {
return noSchema.ViewNames(db)
}
// ViewNames returns the names of the views in this Schema, sorted
// alphabetically.
func (s *Schema) ViewNames(db *sql.DB) ([]string, error) {
return s.masterTableNames(db, "view")
}
// TriggerNames returns the names of the triggers in the main
// database, sorted alphabetically. Use the Schema.TriggerNames
// method to query other databases.
func TriggerNames(db *sql.DB) ([]string, error) {
return noSchema.TriggerNames(db)
}
// TriggerNames returns the names of the triggers in this Schema,
// sorted alphabetically.
func (s *Schema) TriggerNames(db *sql.DB) ([]string, error) {
return s.masterTableNames(db, "trigger")
}
// IndexNames returns the names of the indexes in the main
// database, sorted alphabetically. Use the Schema.IndexNames
// method to query other databases.
func IndexNames(db *sql.DB) ([]string, error) {
return noSchema.IndexNames(db)
}
// IndexNames returns the names of the indexes in this Schema,
// sorted alphabetically.
func (s *Schema) IndexNames(db *sql.DB) ([]string, error) {
return s.masterTableNames(db, "index")
}
// Column represents a column in a table.
type Column struct {
ID int
Name string
Type string
NotNull bool
Default []byte
PrimaryKey int
}
// Columns returns column information for the given table.
//
// If no such table is found in any of the available databases
// (see Multiple Databases above), Columns returns an empty
// slice.
func Columns(db *sql.DB, tableName string) ([]Column, error) {
return noSchema.Columns(db, tableName)
}
// Columns returns column information for the given table.
//
// If no such table is found in this Schema, Columns returns
// an empty slice.
func (s *Schema) Columns(db *sql.DB, tableName string) ([]Column, error) {
params := []interface{}{tableName}
if s.name != "" {
params = append(params, s.name)
}
q :=
`SELECT
cid,
name,
type,
"notnull",
dflt_value,
pk
FROM
pragma_table_info(` + placeholdersFor(params) + `)
ORDER BY
cid`
var columns []Column
err := queryRows(&columns, db, q, params...)
if err != nil {
return nil, fmt.Errorf("could not get columns for table %s: %s", tableName, err)
}
return columns, nil
}
// A ForeignKeyAction describes what happens to the child rows
// of a foreign key when the parent key values are updated or
// deleted.
//
// See https://sqlite.org/foreignkeys.html for more on foreign
// key actions.
type ForeignKeyAction uint
const (
// ForeignKeyActionNone indicates that no special action is
// taken. This is the default behaviour.
ForeignKeyActionNone ForeignKeyAction = iota
// ForeignKeyActionRestrict prohibits the application from
// updating or deleting parent keys.
ForeignKeyActionRestrict
// ForeignKeyActionSetNull sets any child key values to NULL
// when a parent key value is updated or deleted.
ForeignKeyActionSetNull
// ForeignKeyActionSetDefault sets any child key values to
// their defaults when a parent key value is updated or
// deleted.
ForeignKeyActionSetDefault
// ForeignKeyActionCascade propagates parent key changes to
// the child rows. When a parent key value is updated, any
// child key values are similarly updated. When a parent
// key is deleted, any child rows are also deleted.
ForeignKeyActionCascade
)
// Scan implements the sql.Scanner interface.
func (v *ForeignKeyAction) Scan(src interface{}) error {
s, ok := toString(src)
if !ok {
return fmt.Errorf("invalid ForeignKeyAction: %T %v", src, src)
}
switch strings.ToUpper(s) {
case "NO ACTION":
*v = ForeignKeyActionNone
case "RESTRICT":
*v = ForeignKeyActionRestrict
case "SET NULL":
*v = ForeignKeyActionSetNull
case "SET DEFAULT":
*v = ForeignKeyActionSetDefault
case "CASCADE":
*v = ForeignKeyActionCascade
default:
return fmt.Errorf("unsupported ForeignKeyAction: %q", s)
}
return nil
}
// ForeignKey represents a foreign key constraint.
type ForeignKey struct {
ID int
ChildKey []string
ParentTable string
ParentKey []sql.NullString // Parent key fields are NULL if not specified in the REFERENCES clause.
OnUpdate ForeignKeyAction
OnDelete ForeignKeyAction
}
// ForeignKeys returns foreign key information for the given
// table.
//
// If no such table is found in any of the available databases
// (see Multiple Databases above), ForeignKeys returns an empty
// slice.
func ForeignKeys(db *sql.DB, tableName string) ([]ForeignKey, error) {
return noSchema.ForeignKeys(db, tableName)
}
// ForeignKeys returns foreign key information for the given
// table.
//
// If no such table is found in this Schema, ForeignKeys returns
// an empty slice.
func (s *Schema) ForeignKeys(db *sql.DB, tableName string) ([]ForeignKey, error) {
params := []interface{}{tableName}
if s.name != "" {
params = append(params, s.name)
}
q :=
`SELECT
id,
"table",
"from",
"to",
on_update,
on_delete
FROM
pragma_foreign_key_list(` + placeholdersFor(params) + `)
ORDER BY
id, seq`
var rows []struct {
ID int
Table string
From string
To sql.NullString
OnUpdate ForeignKeyAction
OnDelete ForeignKeyAction
}
err := queryRows(&rows, db, q, params...)
if err != nil {
return nil, fmt.Errorf("could not get foreign keys for table %s: %s", tableName, err)
}
var fk *ForeignKey
var foreignKeys []ForeignKey
for _, r := range rows {
if fk == nil || r.ID != fk.ID {
foreignKeys = append(foreignKeys, ForeignKey{
ID: r.ID,
ParentTable: r.Table,
OnUpdate: r.OnUpdate,
OnDelete: r.OnDelete,
})
fk = &foreignKeys[len(foreignKeys)-1]
}
fk.ChildKey = append(fk.ChildKey, r.From)
fk.ParentKey = append(fk.ParentKey, r.To)
}
return foreignKeys, nil
}
// IndexType indicates how an index was created.
type IndexType uint
const (
// IndexTypeUser denotes an index created by the user with
// a CREATE INDEX statement.
IndexTypeUser IndexType = iota
// IndexTypeUnique denotes an index created by SQLite to
// enforce a UNIQUE column constraint.
IndexTypeUnique
// IndexTypePrimaryKey denotes an index created by SQLite
// to enforce a PRIMARY KEY clause.
IndexTypePrimaryKey
)
// Scan implements the sql.Scanner interface.
func (t *IndexType) Scan(src interface{}) error {
s, ok := toString(src)
if !ok {
return fmt.Errorf("invalid IndexType: %T %v", src, src)
}
switch strings.ToLower(s) {
case "c":
*t = IndexTypeUser
case "u":
*t = IndexTypeUnique
case "pk":
*t = IndexTypePrimaryKey
default:
return fmt.Errorf("unsupported IndexType: %q", s)
}
return nil
}
// Index represents an index on a table.
type Index struct {
Name string
Type IndexType
IsUnique bool
IsPartial bool
ColumnNames []sql.NullString // Column names are NULL if the column is an expression (e.g. a+b)
}
// Indexes returns index information for the given table.
//
// If no such table is found in any of the available databases
// (see Multiple Databases above), Indexes returns an empty
// slice.
func Indexes(db *sql.DB, tableName string) ([]Index, error) {
return noSchema.Indexes(db, tableName)
}
// Indexes returns index information for the given table.
//
// If no such table is found in this Schema, Indexes returns
// an empty slice.
func (s *Schema) Indexes(db *sql.DB, tableName string) ([]Index, error) {
placeholder := ""
params := []interface{}{tableName}
if s.name != "" {
placeholder = ", ?"
params = append(params, s.name, s.name)
}
q :=
`SELECT
t1.name,
t1.origin,
t1."unique",
t1.partial,
t2.name
FROM
pragma_index_list(?` + placeholder + `) t1
INNER JOIN
pragma_index_info(t1.name` + placeholder + `) t2
ORDER BY
t1.seq, t2.seqno`
var rows []struct {
Name string
Type IndexType
Unique bool
Partial bool
ColumnName sql.NullString
}
err := queryRows(&rows, db, q, params...)
if err != nil {
return nil, fmt.Errorf("could not get indexes for table %s: %s", tableName, err)
}
var idx *Index
var indexes []Index
for _, r := range rows {
if idx == nil || r.Name != idx.Name {
indexes = append(indexes, Index{
Name: r.Name,
Type: r.Type,
IsUnique: r.Unique,
IsPartial: r.Partial,
})
idx = &indexes[len(indexes)-1]
}
idx.ColumnNames = append(idx.ColumnNames, r.ColumnName)
}
return indexes, nil
}
// TableRankRowID is the TableRank of an IndexColumn that
// represents the ROWID of a table.
const TableRankRowID = -1
// TableRankExpr is the TableRank of an IndexColumn that
// represents an expression rather than a regular table column.
const TableRankExpr = -2
// IndexColumn represents a column in an index.
type IndexColumn struct {
Name sql.NullString // NULL if the column is an expression (e.g. a+b)
Rank int
TableRank int
Descending bool
Collation string
IsKey bool
}
// IndexColumns returns column information for the given index.
//
// If no such index is found in any of the available databases
// (see Multiple Databases above), IndexColumns returns an empty
// slice.
func IndexColumns(db *sql.DB, indexName string) ([]IndexColumn, error) {
return noSchema.IndexColumns(db, indexName)
}
// IndexColumns returns column information for the given index.
//
// If no such index is found in this Schema, IndexColumns returns
// an empty slice.
func (s *Schema) IndexColumns(db *sql.DB, indexName string) ([]IndexColumn, error) {
return s.indexColumns(db, indexName, false)
}
// IndexColumnsAux returns column information for the given
// index. The difference between this function and IndexColumns
// is that IndexColumnsAux includes any auxiliary columns that
// SQLite inserts into the index.
//
// If no such index is found in any of the available databases
// (see Multiple Databases above), IndexColumnsAux returns an
// empty slice.
func IndexColumnsAux(db *sql.DB, indexName string) ([]IndexColumn, error) {
return noSchema.IndexColumnsAux(db, indexName)
}
// IndexColumnsAux returns column information for the given
// index. The difference between this method and IndexColumns
// is that IndexColumnsAux includes any auxiliary columns that
// SQLite inserts into the index.
//
// If no such index is found in this Schema, IndexColumnsAux
// returns an empty slice.
func (s *Schema) IndexColumnsAux(db *sql.DB, indexName string) ([]IndexColumn, error) {
return s.indexColumns(db, indexName, true)
}
func (s *Schema) indexColumns(db *sql.DB, indexName string, includeAux bool) ([]IndexColumn, error) {
params := []interface{}{indexName}
if s.name != "" {
params = append(params, s.name)
}
whereClause := "key = 1"
if includeAux {
whereClause = "1 = 1"
}
q :=
`SELECT
name,
seqno,
cid,
desc,
coll,
key
FROM
pragma_index_xinfo(` + placeholdersFor(params) + `)
WHERE
` + whereClause + `
ORDER BY
seqno`
var columns []IndexColumn
err := queryRows(&columns, db, q, params...)
if err != nil {
return nil, fmt.Errorf("could not get columns for index %s: %s", indexName, err)
}
return columns, nil
}
func (s *Schema) masterTableNames(db *sql.DB, typ string) ([]string, error) {
tableName := "sqlite_master"
if s.name != "" {
if strings.ToLower(s.name) == "temp" {
tableName = "sqlite_temp_master"
} else {
// Unlike the other queries which use parameters, we insert
// the user-provided Schema name directly into the SQL here.
// So to protect against SQL injection, we first verify that
// a database with the given name exists.
ok, err := s.exists(db)
if err != nil {
return nil, fmt.Errorf("could not get %s names: %s", typ, err)
}
if !ok {
return nil, fmt.Errorf("could not get %s names: unknown database '%s'", typ, s.name)
}
tableName = s.name + "." + tableName
}
}
q := fmt.Sprintf("SELECT name FROM %s WHERE type = ? ORDER BY name", tableName)
names, err := queryStrings(db, q, typ)
if err != nil {
return nil, fmt.Errorf("could not get %s names: %s", typ, err)
}
return names, nil
}
func (s *Schema) exists(db *sql.DB) (bool, error) {
var count int
q := "SELECT COUNT(*) FROM pragma_database_list WHERE LOWER(name) = ?"
err := db.QueryRow(q, sqlower(s.name)).Scan(&count)
if err != nil {
return false, err
}
return count > 0, nil
}
// sqlower replicates SQLite's LOWER function which converts
// uppercase ASCII characters in a string to lowercase.
func sqlower(s string) string {
return strings.Map(func(r rune) rune {
if r >= 'A' && r <= 'Z' {
return 'a' + r - 'A'
}
return r
}, s)
}
func toString(v interface{}) (string, bool) {
switch s := v.(type) {
case string:
return s, true
case []byte:
return string(s), true
default:
return "", false
}
}
func placeholdersFor(vals []interface{}) string {
return strings.Join(strings.Split(strings.Repeat("?", len(vals)), ""), ", ")
}