hibernate-orm/design/sql-ast.adoc

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= SQL AST
Ultimately our goal here is to have a `JdbcOperation` object to be executed. Generally, that would look like this:
[source]
----
final SelectStatement sqlAst = ...;
final JdbcServices jdbcServices = sessionFactory.getJdbcServices();
final JdbcEnvironment jdbcEnvironment = jdbcServices.getJdbcEnvironment();
final SqlAstTranslatorFactory sqlAstTranslatorFactory = jdbcEnvironment.getSqlAstTranslatorFactory();
final JdbcSelect jdbcSelect = sqlAstTranslatorFactory.buildSelectTranslator( sessionFactory ).translate( sqlAst );
final JdbcParameterBindings jdbcParameterBindings = new JdbcParameterBindingsImpl( jdbcParameters.size() );
// <fill in parameter bindings>
session.getFactory().getJdbcServices().getJdbcSelectExecutor().list(
jdbcSelect,
jdbcParameterBindings,
...
);
----
== The Tree
The actual tree nodes are defined in the `org.hibernate.sql.ast.tree` package.
== Building SQL AST
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There are 3 main producers of SQL AST:
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SQM:: Translation of HQL and criteria queries. See `org.hibernate.query.sqm.sql`
Loading:: SQL generated for persistence-context events to load entities and collections. This includes `Session#find`, `Session#get`, `Session#lock`, ... See `org.hibernate.loader.internal.MetamodelSelectBuilderProcess`
Mutations:: SQL generated for persistence-context flush events to write entity and collection state to the database. See `org.hibernate.persister.entity.mutation` and `org.hibernate.persister.collection.mutation`
== Translating SQL AST
Translating a SQL AST produces 2 pieces of information needed for executing SQL:
* `org.hibernate.sql.exec.spi.JdbcOperation`
* `org.hibernate.sql.exec.spi.JdbcParameterBindings`
=== JdbcOperation
* `org.hibernate.sql.exec.spi.JdbcDelete`
* `org.hibernate.sql.exec.spi.JdbcInsert`
* `org.hibernate.sql.exec.spi.JdbcSelect`
* `org.hibernate.sql.exec.spi.JdbcUpdate`
=== JdbcParameterBindings
== Execution
=== SELECT execution
`org.hibernate.sql.exec.spi.JdbcSelectExecutor`
=== INSERT, UPDATE, DELETE execution
`org.hibernate.sql.exec.spi.JdbcMutationExecutor`