Preparing queries

If you’re using pgx/v5 you get its implicit support for prepared statements. No additional sqlc configuration is required.

For other drivers, sqlc can give you the option to explicitly use prepared queries. These prepared queries also work with transactions.

You’ll need to set emit_prepared_queries to true in your sqlc configuration to generate code similar to the example below.

CREATE TABLE records (
  id SERIAL PRIMARY KEY
);

-- name: GetRecord :one
SELECT * FROM records
WHERE id = $1;

package db

import (
	"context"
	"database/sql"
	"fmt"
)

type Record struct {
	ID int32
}

type DBTX interface {
	PrepareContext(context.Context, string) (*sql.Stmt, error)
	QueryRowContext(context.Context, string, ...interface{}) *sql.Row
}

func New(db DBTX) *Queries {
	return &Queries{db: db}
}

func Prepare(ctx context.Context, db DBTX) (*Queries, error) {
	q := Queries{db: db}
	var err error
	if q.getRecordStmt, err = db.PrepareContext(ctx, getRecord); err != nil {
		return nil, fmt.Errorf("error preparing query GetRecord: %w", err)
	}
	return &q, nil
}

func (q *Queries) queryRow(ctx context.Context, stmt *sql.Stmt, query string, args ...interface{}) *sql.Row {
	switch {
	case stmt != nil && q.tx != nil:
		return q.tx.StmtContext(ctx, stmt).QueryRowContext(ctx, args...)
	case stmt != nil:
		return stmt.QueryRowContext(ctx, args...)
	default:
		return q.db.QueryRowContext(ctx, query, args...)
	}
}

type Queries struct {
	db            DBTX
	tx            *sql.Tx
	getRecordStmt *sql.Stmt
}

func (q *Queries) WithTx(tx *sql.Tx) *Queries {
	return &Queries{
		db:            tx,
		tx:            tx,
		getRecordStmt: q.getRecordStmt,
	}
}

const getRecord = `-- name: GetRecord :one
SELECT id FROM records
WHERE id = $1
`

func (q *Queries) GetRecord(ctx context.Context, id int32) (int32, error) {
	row := q.queryRow(ctx, q.getRecordStmt, getRecord, id)
	err := row.Scan(&id)
	return id, err
}