Lighter interceptors: more efficient initialization and lower memory usage

[Sanne]

https://hibernate.atlassian.net/browse/HHH-19536

Exploring some internal refactoring of how two core interceptors are being initialized:

• EnhancementAsProxyLazinessInterceptor
• LazyAttributeLoadingInterceptor

(These two are both implementors of of AbstractInterceptor, and represent the full set of its implementors )

The goal is to both reduce allocation pressure significantly, and also reduce the amount of repeating work being done when each of these instances is being initialized. Generally speaking, we identified a significant amount of "state" which is immutable and could be shared across all such interceptor instances when they belong to the same type.

JOL provided stats, assuming 15+ JDK, COOPS, CCPS :

Before:

org.hibernate.bytecode.enhance.spi.interceptor.EnhancementAsProxyLazinessInterceptor object internals:
OFF  SZ                               TYPE DESCRIPTION                                                      VALUE
  0   8                                    (object header: mark)                                            N/A
  8   4                                    (object header: class)                                           N/A
 12   1                            boolean AbstractInterceptor.allowLoadOutsideTransaction                  N/A
 13   1                            boolean EnhancementAsProxyLazinessInterceptor.inLineDirtyChecking        N/A
 14   1                            boolean EnhancementAsProxyLazinessInterceptor.initializeBeforeWrite      N/A
 15   1                                    (alignment/padding gap)                                          
 16   4                             String AbstractInterceptor.entityName                                   N/A
 20   4   SharedSessionContractImplementor AbstractInterceptor.session                                      N/A
 24   4                             String AbstractInterceptor.sessionFactoryUuid                           N/A
 28   4                        Set<String> EnhancementAsProxyLazinessInterceptor.identifierAttributeNames   N/A
 32   4                      CompositeType EnhancementAsProxyLazinessInterceptor.nonAggregatedCidMapper     N/A
 36   4                          EntityKey EnhancementAsProxyLazinessInterceptor.entityKey                  N/A
 40   4                        Set<String> EnhancementAsProxyLazinessInterceptor.writtenFieldNames          N/A
 44   4                        Set<String> EnhancementAsProxyLazinessInterceptor.collectionAttributeNames   N/A
 48   4                             Status EnhancementAsProxyLazinessInterceptor.status                     N/A
 52   4                                    (object alignment gap)                                           
Instance size: 56 bytes
Space losses: 1 bytes internal + 4 bytes external = 5 bytes total

org.hibernate.bytecode.enhance.spi.interceptor.LazyAttributeLoadingInterceptor object internals:
OFF  SZ                               TYPE DESCRIPTION                                             VALUE
  0   8                                    (object header: mark)                                   N/A
  8   4                                    (object header: class)                                  N/A
 12   1                            boolean AbstractInterceptor.allowLoadOutsideTransaction         N/A
 13   3                                    (alignment/padding gap)                                 
 16   4                             String AbstractInterceptor.entityName                          N/A
 20   4   SharedSessionContractImplementor AbstractInterceptor.session                             N/A
 24   4                             String AbstractInterceptor.sessionFactoryUuid                  N/A
 28   4                             Object LazyAttributeLoadingInterceptor.identifier              N/A
 32   4                        Set<String> LazyAttributeLoadingInterceptor.lazyFields              N/A
 36   4                        Set<String> LazyAttributeLoadingInterceptor.initializedLazyFields   N/A
 40   4                        Set<String> LazyAttributeLoadingInterceptor.mutableLazyFields       N/A
 44   4                                    (object alignment gap)                                  
Instance size: 48 bytes
Space losses: 3 bytes internal + 4 bytes external = 7 bytes total

After:

org.hibernate.bytecode.enhance.spi.interceptor.EnhancementAsProxyLazinessInterceptor object internals:
OFF  SZ                        TYPE DESCRIPTION                                               VALUE
  0   8                             (object header: mark)                                     N/A
  8   4                             (object header: class)                                    N/A
 12   4   SessionAssociationMarkers AbstractInterceptor.sessionAssociation                    N/A
 16   4                   EntityKey EnhancementAsProxyLazinessInterceptor.entityKey           N/A
 20   4          EntityRelatedState EnhancementAsProxyLazinessInterceptor.meta                N/A
 24   4                 Set<String> EnhancementAsProxyLazinessInterceptor.writtenFieldNames   N/A
 28   4                      Status EnhancementAsProxyLazinessInterceptor.status              N/A
Instance size: 32 bytes
Space losses: 0 bytes internal + 0 bytes external = 0 bytes total


org.hibernate.bytecode.enhance.spi.interceptor.LazyAttributeLoadingInterceptor object internals:
OFF  SZ                        TYPE DESCRIPTION                                             VALUE
  0   8                             (object header: mark)                                   N/A
  8   4                             (object header: class)                                  N/A
 12   4   SessionAssociationMarkers AbstractInterceptor.sessionAssociation                  N/A
 16   4                      Object LazyAttributeLoadingInterceptor.identifier              N/A
 20   4          EntityRelatedState LazyAttributeLoadingInterceptor.entityMeta              N/A
 24   4                 Set<String> LazyAttributeLoadingInterceptor.initializedLazyFields   N/A
 28   4                             (object alignment gap)                                  
Instance size: 32 bytes
Space losses: 0 bytes internal + 4 bytes external = 4 bytes total

This exploration also led to rethink how we model the association of such an interceptor to the current Session, also providing both memory and computational benefits. Code comments hopefully explain this in more detail.

(fully relies on all existing tests)

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https://hibernate.atlassian.net/browse/HHH-19536

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