cloudflared-mirror/dbconnect/sql.go

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package dbconnect
import (
"context"
"database/sql"
"encoding/json"
"fmt"
"net/url"
"reflect"
"strings"
"github.com/jmoiron/sqlx"
"github.com/pkg/errors"
"github.com/xo/dburl"
// SQL drivers self-register with the database/sql package.
// https://github.com/golang/go/wiki/SQLDrivers
_ "github.com/denisenkom/go-mssqldb"
_ "github.com/go-sql-driver/mysql"
_ "github.com/mattn/go-sqlite3"
"github.com/kshvakov/clickhouse"
"github.com/lib/pq"
)
// SQLClient is a Client that talks to a SQL database.
type SQLClient struct {
Dialect string
driver *sqlx.DB
}
// NewSQLClient creates a SQL client based on its URL scheme.
func NewSQLClient(ctx context.Context, originURL *url.URL) (Client, error) {
res, err := dburl.Parse(originURL.String())
if err != nil {
helpText := fmt.Sprintf("supported drivers: %+q, see documentation for more details: %s", sql.Drivers(), "https://godoc.org/github.com/xo/dburl")
return nil, fmt.Errorf("could not parse sql database url '%s': %s\n%s", originURL, err.Error(), helpText)
}
// Establishes the driver, but does not test the connection.
driver, err := sqlx.Open(res.Driver, res.DSN)
if err != nil {
return nil, fmt.Errorf("could not open sql driver %s: %s\n%s", res.Driver, err.Error(), res.DSN)
}
// Closes the driver, will occur when the context finishes.
go func() {
<-ctx.Done()
_ = driver.Close()
}()
return &SQLClient{driver.DriverName(), driver}, nil
}
// Ping verifies a connection to the database is still alive.
func (client *SQLClient) Ping(ctx context.Context) error {
return client.driver.PingContext(ctx)
}
// Submit queries or executes a command to the SQL database.
func (client *SQLClient) Submit(ctx context.Context, cmd *Command) (interface{}, error) {
txx, err := cmd.ValidateSQL(client.Dialect)
if err != nil {
return nil, err
}
ctx, cancel := context.WithTimeout(ctx, cmd.Timeout)
defer cancel()
var res interface{}
// Get the next available sql.Conn and submit the Command.
err = sqlConn(ctx, client.driver, txx, func(conn *sql.Conn) error {
stmt := cmd.Statement
args := cmd.Arguments.Positional
if cmd.Mode == "query" {
res, err = sqlQuery(ctx, conn, stmt, args)
} else {
res, err = sqlExec(ctx, conn, stmt, args)
}
return err
})
return res, err
}
// ValidateSQL extends the contract of Command for SQL dialects:
// mode is conformed, arguments are []sql.NamedArg, and isolation is a sql.IsolationLevel.
//
// When the command should not be wrapped in a transaction, *sql.TxOptions and error will both be nil.
func (cmd *Command) ValidateSQL(dialect string) (*sql.TxOptions, error) {
err := cmd.Validate()
if err != nil {
return nil, err
}
mode, err := sqlMode(cmd.Mode)
if err != nil {
return nil, err
}
// Mutates Arguments to only use positional arguments with the type sql.NamedArg.
// This is a required by the sql.Driver before submitting arguments.
cmd.Arguments.sql(dialect)
iso, err := sqlIsolation(cmd.Isolation)
if err != nil {
return nil, err
}
// When isolation is out-of-range, this is indicative that no
// transaction should be executed and sql.TxOptions should be nil.
if iso < sql.LevelDefault {
return nil, nil
}
// In query mode, execute the transaction in read-only, unless it's Microsoft SQL
// which does not support that type of transaction.
readOnly := mode == "query" && dialect != "mssql"
return &sql.TxOptions{Isolation: iso, ReadOnly: readOnly}, nil
}
// sqlConn gets the next available sql.Conn in the connection pool and runs a function to use it.
//
// If the transaction options are nil, run the useIt function outside a transaction.
// This is potentially an unsafe operation if the command does not clean up its state.
func sqlConn(ctx context.Context, driver *sqlx.DB, txx *sql.TxOptions, useIt func(*sql.Conn) error) error {
conn, err := driver.Conn(ctx)
if err != nil {
return err
}
defer conn.Close()
// If transaction options are specified, begin and defer a rollback to catch errors.
var tx *sql.Tx
if txx != nil {
tx, err = conn.BeginTx(ctx, txx)
if err != nil {
return err
}
defer tx.Rollback()
}
err = useIt(conn)
// Check if useIt was successful and a transaction exists before committing.
if err == nil && tx != nil {
err = tx.Commit()
}
return err
}
// sqlQuery queries rows on a sql.Conn and returns an array of result objects.
func sqlQuery(ctx context.Context, conn *sql.Conn, stmt string, args []interface{}) ([]map[string]interface{}, error) {
rows, err := conn.QueryContext(ctx, stmt, args...)
if err == nil {
return sqlRows(rows)
}
return nil, err
}
// sqlExec executes a command on a sql.Conn and returns the result of the operation.
func sqlExec(ctx context.Context, conn *sql.Conn, stmt string, args []interface{}) (sqlResult, error) {
exec, err := conn.ExecContext(ctx, stmt, args...)
if err == nil {
return sqlResultFrom(exec), nil
}
return sqlResult{}, err
}
// sql mutates Arguments to contain a positional []sql.NamedArg.
//
// The actual return type is []interface{} due to the native Golang
// function signatures for sql.Exec and sql.Query being generic.
func (args *Arguments) sql(dialect string) {
result := args.Positional
for i, val := range result {
result[i] = sqlArg("", val, dialect)
}
for key, val := range args.Named {
result = append(result, sqlArg(key, val, dialect))
}
args.Positional = result
args.Named = map[string]interface{}{}
}
// sqlArg creates a sql.NamedArg from a key-value pair and an optional dialect.
//
// Certain dialects will need to wrap objects, such as arrays, to conform its driver requirements.
func sqlArg(key, val interface{}, dialect string) sql.NamedArg {
switch reflect.ValueOf(val).Kind() {
// PostgreSQL and Clickhouse require arrays to be wrapped before
// being inserted into the driver interface.
case reflect.Slice, reflect.Array:
switch dialect {
case "postgres":
val = pq.Array(val)
case "clickhouse":
val = clickhouse.Array(val)
}
}
return sql.Named(fmt.Sprint(key), val)
}
// sqlIsolation tries to match a string to a sql.IsolationLevel.
func sqlIsolation(str string) (sql.IsolationLevel, error) {
if str == "none" {
return sql.IsolationLevel(-1), nil
}
for iso := sql.LevelDefault; ; iso++ {
if iso > sql.LevelLinearizable {
return -1, fmt.Errorf("cannot provide an invalid sql isolation level: '%s'", str)
}
if str == "" || strings.EqualFold(iso.String(), strings.ReplaceAll(str, "_", " ")) {
return iso, nil
}
}
}
// sqlMode tries to match a string to a command mode: 'query' or 'exec' for now.
func sqlMode(str string) (string, error) {
switch str {
case "query", "exec":
return str, nil
default:
return "", fmt.Errorf("cannot provide invalid sql mode: '%s'", str)
}
}
// sqlRows scans through a SQL result set and returns an array of objects.
func sqlRows(rows *sql.Rows) ([]map[string]interface{}, error) {
columns, err := rows.Columns()
if err != nil {
return nil, errors.Wrap(err, "could not extract columns from result")
}
defer rows.Close()
types, err := rows.ColumnTypes()
if err != nil {
// Some drivers do not support type extraction, so fail silently and continue.
types = make([]*sql.ColumnType, len(columns))
}
values := make([]interface{}, len(columns))
pointers := make([]interface{}, len(columns))
var results []map[string]interface{}
for rows.Next() {
for i := range columns {
pointers[i] = &values[i]
}
_ = rows.Scan(pointers...)
// Convert a row, an array of values, into an object where
// each key is the name of its respective column.
entry := make(map[string]interface{})
for i, col := range columns {
entry[col] = sqlValue(values[i], types[i])
}
results = append(results, entry)
}
return results, nil
}
// sqlValue handles special cases where sql.Rows does not return a "human-readable" object.
func sqlValue(val interface{}, col *sql.ColumnType) interface{} {
bytes, ok := val.([]byte)
if ok {
// Opportunistically check for embeded JSON and convert it to a first-class object.
var embeded interface{}
if json.Unmarshal(bytes, &embeded) == nil {
return embeded
}
// STOR-604: investigate a way to coerce PostgreSQL arrays '{a, b, ...}' into JSON.
// Although easy with strings, it becomes more difficult with special types like INET[].
return string(bytes)
}
return val
}
// sqlResult is a thin wrapper around sql.Result.
type sqlResult struct {
LastInsertId int64 `json:"last_insert_id"`
RowsAffected int64 `json:"rows_affected"`
}
// sqlResultFrom converts sql.Result into a JSON-marshable sqlResult.
func sqlResultFrom(res sql.Result) sqlResult {
insertID, errID := res.LastInsertId()
rowsAffected, errRows := res.RowsAffected()
// If an error occurs when extracting the result, it is because the
// driver does not support that specific field. Instead of passing this
// to the user, omit the field in the response.
if errID != nil {
insertID = -1
}
if errRows != nil {
rowsAffected = -1
}
return sqlResult{insertID, rowsAffected}
}