Method Prepare

conn.go:319–372

Prepare creates a prepared statement with name and sql. sql can contain placeholders for bound parameters. These placeholders are referenced positionally as $1, $2, etc. name can be used instead of sql with [Conn.Query], [Conn.QueryRow], and [Conn.Exec] to execute the statement. It can also be used

(ctx context.Context, name, sql string)

// Prepare is idempotent; i.e. it is safe to call Prepare multiple times with the same name and sql arguments. This
// allows a code path to Prepare and Query/Exec without concern for if the statement has already been prepared.
func (c *Conn) Prepare(ctx context.Context, name, sql string) (sd *pgconn.StatementDescription, err error) {
	if c.failedDescribeStatement != "" {
		err = c.Deallocate(ctx, c.failedDescribeStatement)
		if err != nil {
			return nil, fmt.Errorf("failed to deallocate previously failed statement %q: %w", c.failedDescribeStatement, err)
		}
		c.failedDescribeStatement = ""
	}

	if c.prepareTracer != nil {
		ctx = c.prepareTracer.TracePrepareStart(ctx, c, TracePrepareStartData{Name: name, SQL: sql})
	}

	if name != "" {
		var ok bool
		if sd, ok = c.preparedStatements[name]; ok && sd.SQL == sql {
			if c.prepareTracer != nil {
				c.prepareTracer.TracePrepareEnd(ctx, c, TracePrepareEndData{AlreadyPrepared: true})
			}
			return sd, nil
		}
	}

	if c.prepareTracer != nil {
		defer func() {
			c.prepareTracer.TracePrepareEnd(ctx, c, TracePrepareEndData{Err: err})
		}()
	}

	var psName, psKey string
	if name == sql {
		digest := sha256.Sum256([]byte(sql))
		psName = "stmt_" + hex.EncodeToString(digest[0:24])
		psKey = sql
	} else {
		psName = name
		psKey = name
	}

	sd, err = c.pgConn.Prepare(ctx, psName, sql, nil)
	if err != nil {
		var pErr *pgconn.PrepareError
		if errors.As(err, &pErr) {
			c.failedDescribeStatement = psKey
		}
		return nil, err
	}

	if psKey != "" {
		c.preparedStatements[psKey] = sd
	}

	return sd, nil
}

// Deallocate releases a prepared statement. Calling Deallocate on a non-existent prepared statement will succeed.
func (c *Conn) Deallocate(ctx context.Context, name string) error {