new doc section on slow queries and SQL comments

documentation/src/main/asciidoc/introduction/Introduction.adoc

@@ -619,20 +619,16 @@ It might return a single `Book`.
 
 [source,java]
 ----
-interface Queries {
+@HQL("from Book where isbn = :isbn")
-    @HQL("from Book where isbn = :isbn")
+Book findBookByIsbn(String isbn);
-    Book findBookByIsbn(String isbn);
-}
 ----
 
 It might even return `TypedQuery` or `SelectionQuery`:
 
 [source,java]
 ----
-interface Queries {
+@HQL("from Book where title like :title")
-    @HQL("from Book where title like :title")
+SelectionQuery<Book> findBooksByTitle(String title);
-    SelectionQuery<Book> findBooksByTitle(String title);
-}
 ----
 
 This is extremely useful at times, since it allows the client to further manipulate the query:
@@ -641,9 +637,12 @@ This is extremely useful at times, since it allows the client to further manipul
 ----
 List<Book> books =
         Queries_.findBooksByTitle(entityManager, titlePattern)
-            .ascending(Book_.title)                   // order the results
+            .setOrder(Order.asc(Book_.title))                   // order the results
-            .setMaxResults(RESULTS_PER_PAGE)          // return at most 20 results
+            .setPage(Page.page(RESULTS_PER_PAGE, page))         // return the given page of results
-            .setFirstResult(page*RESULTS_PER_PAGE)    // start from the given page of results
+            .setFlushMode(FlushModeType.COMMIT)                 // don't flush session before query execution
+            .setReadOnly(true)                                  // load the entities in read-only mode
+            .setCacheStoreMode(CacheStoreMode.BYPASS)           // don't cache the results
+            .setComment("Hello world!")                         // add a comment to the generated SQL
             .getResultList();
 ----
 

documentation/src/main/asciidoc/introduction/Tuning.adoc

@@ -980,6 +980,28 @@ long publisherCacheMissCount =
 Hibernate's statistics enable observability.
 Both {micrometer}[Micrometer] and {smallrye-metrics}[SmallRye Metrics] are capable of exposing these metrics.
 
+[[slow-queries]]
+=== Tracking down slow queries
+
+When a poorly-performing SQL query is discovered in production, it can sometimes be hard to track down exactly where in the Java code the query originates.
+Hibernate offers two configuration properties that can make it easier to identify a slow query and find its source.
+
+.Settings for tracking slow queries
+[%breakable,cols="25,~,~"]
+|===
+| Configuration property name | Purpose | Property value
+
+| `hibernate.log_slow_query` | Log slow queries at the `INFO` level | The minimum execution time, in milliseconds, which characterizes a "slow" query
+| `hibernate.use_sql_comments` | Prepend comments to the executed SQL | `true` or `false`
+|===
+
+When `hibernate.use_sql_comments` is enabled, the text of the HQL query is prepended as a comment to the generated SQL, which usually makes it easy to find the HQL in the Java code.
+
+The comment text may be customized:
+
+- by calling `Query.setComment(comment)` or `Query.setHint(AvailableHints.HINT_COMMENT,comment)`, or
+- via the `@NamedQuery` annotation.
+
 [[hibernate-reactive]]
 === Reactive programming with Hibernate