# Migrate from Pydantic v1 to Pydantic v2 { #migrate-from-pydantic-v1-to-pydantic-v2 }

If you have an old FastAPI app, you might be using Pydantic version 1.

FastAPI version 0.100.0 had support for either Pydantic v1 or v2. It would use whichever you had installed.

FastAPI version 0.119.0 introduced partial support for Pydantic v1 from inside of Pydantic v2 (as `pydantic.v1`), to facilitate the migration to v2.

            }
            buffer.append(proxy.getHost()).append(':').append(proxy.getPort()).append('>');
        }

        // consider the username&password because a repo manager might block artifacts depending on authorization
        Authentication auth = repository.getAuthentication();
        if (auth != null) {
            int hash = (auth.getUsername() + auth.getPassword()).hashCode();

     * <p><b>Performance note:</b> the returned array is backed by the same array as the builder, so
     * no data is copied as part of this step, but this may occupy more memory than strictly
     * necessary. To copy the data to a right-sized backing array, use {@code .build().trimmed()}.
     */
    public ImmutableLongArray build() {
      return count == 0 ? EMPTY : new ImmutableLongArray(array, 0, count);
    }
  }

  // Instance stuff here

            //
            // We promise this because, once we cancel that Future, we would no longer be able to
            // tell when any underlying work it is doing is done. Thus, we might start a new task
            // while that underlying work is still running.
            //
            // So that is why we cancel only in the case of CAS success.
            taskFuture.cancel(false);
          }

     * <p><b>Performance note:</b> the returned array is backed by the same array as the builder, so
     * no data is copied as part of this step, but this may occupy more memory than strictly
     * necessary. To copy the data to a right-sized backing array, use {@code .build().trimmed()}.
     */
    public ImmutableIntArray build() {
      return count == 0 ? EMPTY : new ImmutableIntArray(array, 0, count);
    }
  }

  // Instance stuff here

     * field should be used for calculating that. This would likely be zero
     * but an implemantation that encorporates the transport header(for
     * efficiency) might use a different initial bufferIndex. For example,
     * to eliminate copying data when writing NbtSession data one might
     * manage that 4 byte header specifically and therefore the initial
     * bufferIndex, and thus headerStart, would be 4).(NOTE: If one where

     * implemented. A <code>scope</code> of <code>null</code> or <code>""</code>
     * signifies no scope.
     *
     * The additional <code>svr</code> parameter specifies the address to
     * query. This might be the address of a specific host, a name server,
     * or a broadcast address.
     *
     * @param host
     *            the name to resolve
     * @param type
     *            the hex code of the name

   * expect a newly-started thread to call [Runnable.run]. We shouldn't request new threads until
   * the already-requested ones are in service, otherwise we might create more threads than we need.
   *
   * We use [executeCallCount] and [runCallCount] to defend against starting more threads than we
   * need. Both fields are guarded by `this`.
   */
  private var executeCallCount = 0

            // mvn remote-resources:process
            //
            // From the metadata stored on the server which has been created as part of a standard
            // Maven plugin deployment we will find the right PluginDescriptor from the remote
            // repository.

            plugin = findPluginForPrefix(prefix, session);
        }

        int executionIdx = goal.indexOf("@");
        if (executionIdx > 0) {

//     specific system recommendations based on current support case statistics and storage performance possibilities.
//     Vendors might change the settings based on the configuration and scale out of the solution (more storage nodes =>
//     higher task limit).
//
//     <S3ConcurrentTaskLimit>
//