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// Copyright 2020 The Matrix.org Foundation C.I.C.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package sqlutil
import (
"context"
"database/sql"
"errors"
"fmt"
"strings"
"github.com/matrix-org/util"
)
// ErrUserExists is returned if a username already exists in the database.
var ErrUserExists = errors.New("username already exists")
// A Transaction is something that can be committed or rolledback.
type Transaction interface {
// Commit the transaction
Commit() error
// Rollback the transaction.
Rollback() error
}
// EndTransaction ends a transaction.
// If the transaction succeeded then it is committed, otherwise it is rolledback.
// You MUST check the error returned from this function to be sure that the transaction
// was applied correctly. For example, 'database is locked' errors in sqlite will happen here.
func EndTransaction(txn Transaction, succeeded *bool) error {
if *succeeded {
return txn.Commit()
} else {
return txn.Rollback()
}
}
// EndTransactionWithCheck ends a transaction and overwrites the error pointer if its value was nil.
// If the transaction succeeded then it is committed, otherwise it is rolledback.
// Designed to be used with defer (see EndTransaction otherwise).
func EndTransactionWithCheck(txn Transaction, succeeded *bool, err *error) {
if e := EndTransaction(txn, succeeded); e != nil && *err == nil {
*err = e
}
}
// WithTransaction runs a block of code passing in an SQL transaction
// If the code returns an error or panics then the transactions is rolledback
// Otherwise the transaction is committed.
func WithTransaction(db *sql.DB, fn func(txn *sql.Tx) error) (err error) {
txn, err := db.Begin()
if err != nil {
return fmt.Errorf("sqlutil.WithTransaction.Begin: %w", err)
}
succeeded := false
defer EndTransactionWithCheck(txn, &succeeded, &err)
err = fn(txn)
if err != nil {
return
}
succeeded = true
return
}
// TxStmt wraps an SQL stmt inside an optional transaction.
// If the transaction is nil then it returns the original statement that will
// run outside of a transaction.
// Otherwise returns a copy of the statement that will run inside the transaction.
func TxStmt(transaction *sql.Tx, statement *sql.Stmt) *sql.Stmt {
if transaction != nil {
statement = transaction.Stmt(statement)
}
return statement
}
// TxStmtContext behaves similarly to TxStmt, with support for also passing context.
func TxStmtContext(context context.Context, transaction *sql.Tx, statement *sql.Stmt) *sql.Stmt {
if transaction != nil {
statement = transaction.StmtContext(context, statement)
}
return statement
}
// Hack of the century
func QueryVariadic(count int) string {
return QueryVariadicOffset(count, 0)
}
func QueryVariadicOffset(count, offset int) string {
str := "("
for i := 0; i < count; i++ {
str += fmt.Sprintf("$%d", i+offset+1)
if i < (count - 1) {
str += ", "
}
}
str += ")"
return str
}
func minOfInts(a, b int) int {
if a <= b {
return a
}
return b
}
// QueryProvider defines the interface for querys used by RunLimitedVariablesQuery.
type QueryProvider interface {
QueryContext(ctx context.Context, query string, args ...interface{}) (*sql.Rows, error)
}
// SQLite3MaxVariables is the default maximum number of host parameters in a single SQL statement
// SQLlite can handle. See https://www.sqlite.org/limits.html for more information.
const SQLite3MaxVariables = 999
// RunLimitedVariablesQuery split up a query with more variables than the used database can handle in multiple queries.
func RunLimitedVariablesQuery(ctx context.Context, query string, qp QueryProvider, variables []interface{}, limit uint, rowHandler func(*sql.Rows) error) error {
var start int
for start < len(variables) {
n := minOfInts(len(variables)-start, int(limit))
nextQuery := strings.Replace(query, "($1)", QueryVariadic(n), 1)
rows, err := qp.QueryContext(ctx, nextQuery, variables[start:start+n]...)
if err != nil {
util.GetLogger(ctx).WithError(err).Error("QueryContext returned an error")
return err
}
err = rowHandler(rows)
if closeErr := rows.Close(); closeErr != nil {
util.GetLogger(ctx).WithError(closeErr).Error("RunLimitedVariablesQuery: failed to close rows")
return err
}
if err != nil {
util.GetLogger(ctx).WithError(err).Error("RunLimitedVariablesQuery: rowHandler returned error")
return err
}
start = start + n
}
return nil
}
// StatementList is a list of SQL statements to prepare and a pointer to where to store the resulting prepared statement.
type StatementList []struct {
Statement **sql.Stmt
SQL string
}
// Prepare the SQL for each statement in the list and assign the result to the prepared statement.
func (s StatementList) Prepare(db *sql.DB) (err error) {
for _, statement := range s {
if *statement.Statement, err = db.Prepare(statement.SQL); err != nil {
err = fmt.Errorf("Error %q while preparing statement: %s", err, statement.SQL)
return
}
}
return
}
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