Carlos Florêncio
79 lines
2.1 KiB
Go
79 lines
2.1 KiB
Go
package db
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import "database/sql"
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// SchemaQuerier is the subset of sqlx database and transaction methods used
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// by the portable schema probes.
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type SchemaQuerier interface {
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DriverName() string
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Query(string, ...any) (*sql.Rows, error)
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QueryRow(string, ...any) *sql.Row
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Rebind(string) string
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}
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// TableExists reports whether table exists in the active database schema.
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// Missing tables are reported as false without an error.
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func TableExists(conn SchemaQuerier, table string) (bool, error) {
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query := `SELECT EXISTS (
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SELECT 1 FROM information_schema.tables
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WHERE table_schema = current_schema() AND table_name = ?
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)`
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if !isPostgresSchema(conn) {
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query = `SELECT EXISTS (
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SELECT 1 FROM sqlite_master
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WHERE type = 'table' AND name = ?
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)`
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}
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var exists bool
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if err := conn.QueryRow(conn.Rebind(query), table).Scan(&exists); err != nil {
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return false, err
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}
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return exists, nil
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}
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// TableColumns returns the column names declared by table. An absent table is
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// reported as an empty map without an error.
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func TableColumns(conn SchemaQuerier, table string) (map[string]bool, error) {
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query := `SELECT column_name
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FROM information_schema.columns
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WHERE table_schema = current_schema() AND table_name = ?
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ORDER BY ordinal_position`
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if !isPostgresSchema(conn) {
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query = `SELECT name FROM pragma_table_info(?) ORDER BY cid`
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}
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rows, err := conn.Query(conn.Rebind(query), table)
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if err != nil {
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return nil, err
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}
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defer func() { _ = rows.Close() }()
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columns := make(map[string]bool)
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for rows.Next() {
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var name string
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if err := rows.Scan(&name); err != nil {
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return nil, err
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}
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columns[name] = true
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}
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if err := rows.Err(); err != nil {
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return nil, err
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}
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return columns, nil
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}
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// ColumnExists reports whether table declares column. Missing tables and
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// columns are reported as false without an error.
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func ColumnExists(conn SchemaQuerier, table, column string) (bool, error) {
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columns, err := TableColumns(conn, table)
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if err != nil {
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return false, err
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}
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return columns[column], nil
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}
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func isPostgresSchema(conn SchemaQuerier) bool {
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return conn.DriverName() == "pgx"
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}
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