func()

in conn.go [1397:1471]
58 lines of code
12 McCabe index (conditional complexity)

func (c *Conn) prepareStatement(ctx context.Context, stmt string, tracer Tracer, keyspace string) (*preparedStatment, error) {
	stmtCacheKey := c.session.stmtsLRU.keyFor(c.host.HostID(), keyspace, stmt)
	flight, ok := c.session.stmtsLRU.execIfMissing(stmtCacheKey, func(lru *lru.Cache) *inflightPrepare {
		flight := &inflightPrepare{
			done: make(chan struct{}),
		}
		lru.Add(stmtCacheKey, flight)
		return flight
	})

	if !ok {
		go func() {
			defer close(flight.done)

			prep := &writePrepareFrame{
				statement: stmt,
			}
			if c.version > protoVersion4 {
				prep.keyspace = keyspace
			}

			// we won the race to do the load, if our context is canceled we shouldnt
			// stop the load as other callers are waiting for it but this caller should get
			// their context cancelled error.
			framer, err := c.exec(c.ctx, prep, tracer)
			if err != nil {
				flight.err = err
				c.session.stmtsLRU.remove(stmtCacheKey)
				return
			}

			frame, err := framer.parseFrame()
			if err != nil {
				flight.err = err
				c.session.stmtsLRU.remove(stmtCacheKey)
				return
			}

			// TODO(zariel): tidy this up, simplify handling of frame parsing so its not duplicated
			// everytime we need to parse a frame.
			if len(framer.traceID) > 0 && tracer != nil {
				tracer.Trace(framer.traceID)
			}

			switch x := frame.(type) {
			case *resultPreparedFrame:
				flight.preparedStatment = &preparedStatment{
					// defensively copy as we will recycle the underlying buffer after we
					// return.
					id:               copyBytes(x.preparedID),
					resultMetadataID: copyBytes(x.resultMetadataID),
					// the type info's should _not_ have a reference to the framers read buffer,
					// therefore we can just copy them directly.
					request:  x.reqMeta,
					response: x.respMeta,
				}
			case error:
				flight.err = x
			default:
				flight.err = NewErrProtocol("Unknown type in response to prepare frame: %s", x)
			}

			if flight.err != nil {
				c.session.stmtsLRU.remove(stmtCacheKey)
			}
		}()
	}

	select {
	case <-ctx.Done():
		return nil, ctx.Err()
	case <-flight.done:
		return flight.preparedStatment, flight.err
	}
}