介紹

JDBC長期以來一直為DML語句批處理提供支持。 默認情況下，所有語句都一個接一個地發送，每個語句都在單獨的網絡往返中發送。 批處理使我們能夠一次性發送多個語句，從而節省了不必要的套接字流刷新。

Hibernate將數據庫語句隱藏在事務后寫抽象層的后面 。 中間層允許我們從持久層邏輯中隱藏JDBC批處理語義。 這樣，我們可以更改JDBC批處理策略，而無需更改數據訪問代碼。

配置Hibernate來支持JDBC批處理并不是那么容易，所以我將解釋為使其工作所需要做的一切。

測試時間

我們將從以下實體模型開始：

該帖子與Comment實體具有一對多關聯：

@OneToMany(cascade = CascadeType.ALL, mappedBy = "post", orphanRemoval = true) private List<Comment> comments = new ArrayList<>();

或者測試場景同時發出INSERT和UPDATE語句，因此我們可以驗證是否正在使用JDBC批處理：

LOGGER.info("Test batch insert"); long startNanos = System.nanoTime(); doInTransaction(session -> {int batchSize = batchSize();for(int i = 0; i < itemsCount(); i++) {Post post = new Post(String.format("Post no. %d", i));int j = 0;post.addComment(new Comment(String.format("Post comment %d:%d", i, j++)));post.addComment(new Comment(String.format("Post comment %d:%d", i, j++)));session.persist(post);if(i % batchSize == 0 && i > 0) {session.flush();session.clear();}} }); LOGGER.info("{}.testInsert took {} millis",getClass().getSimpleName(),TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNanos));LOGGER.info("Test batch update"); startNanos = System.nanoTime();doInTransaction(session -> {List<Post> posts = session.createQuery("select distinct p " +"from Post p " +"join fetch p.comments c").list();for(Post post : posts) {post.title = "Blog " + post.title;for(Comment comment : post.comments) {comment.review = "Blog " + comment.review;}} });LOGGER.info("{}.testUpdate took {} millis",getClass().getSimpleName(),TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNanos));

該測試將保留可配置數量的Post實體，每個實體包含兩個Comment 。 為了簡潔起見，我們將保留3個帖子和方言的默認批處理大小：

protected int itemsCount() {return 3; }protected int batchSize() {return Integer.valueOf(Dialect.DEFAULT_BATCH_SIZE); }

默認批處理支持

Hibernate不會隱式使用JDBC批處理，并且每個INSERT和UPDATE語句都是分別執行的：

Query:{[insert into Post (title, version, id) values (?, ?, ?)][Post no. 0,0,1]} Query:{[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][1,Post comment 0:0,0,51]} Query:{[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][1,Post comment 0:1,0,52]} Query:{[insert into Post (title, version, id) values (?, ?, ?)][Post no. 1,0,2]} Query:{[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][2,Post comment 1:0,0,53]} Query:{[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][2,Post comment 1:1,0,54]} Query:{[insert into Post (title, version, id) values (?, ?, ?)][Post no. 2,0,3]} Query:{[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][3,Post comment 2:0,0,55]} Query:{[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][3,Post comment 2:1,0,56]}Query:{[update Post set title=?, version=? where id=? and version=?][Blog Post no. 1,1,2,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][2,Blog Post comment 1:0,1,53,0]} Query:{[update Post set title=?, version=? where id=? and version=?][Blog Post no. 0,1,1,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][1,Blog Post comment 0:1,1,52,0]} Query:{[update Post set title=?, version=? where id=? and version=?][Blog Post no. 2,1,3,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][3,Blog Post comment 2:0,1,55,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][3,Blog Post comment 2:1,1,56,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][1,Blog Post comment 0:0,1,51,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][2,Blog Post comment 1:1,1,54,0]}

配置

要啟用JDBC批處理，我們必須配置hibernate.jdbc.batch_size屬性：

非零值允許Hibernate使用JDBC2批處理更新（例如，建議值介于5到30之間）

我們將設置此屬性并重新運行測試：

properties.put("hibernate.jdbc.batch_size", String.valueOf(batchSize()));

這次，批處理Comment INSERT語句，而UPDATE語句保持不變：

Query:{[insert into Post (title, version, id) values (?, ?, ?)][Post no. 0,0,1]} Query:{[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][1,Post comment 0:0,0,51]} {[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][1,Post comment 0:1,0,52]} Query:{[insert into Post (title, version, id) values (?, ?, ?)][Post no. 1,0,2]} Query:{[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][2,Post comment 1:0,0,53]} {[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][2,Post comment 1:1,0,54]} Query:{[insert into Post (title, version, id) values (?, ?, ?)][Post no. 2,0,3]} Query:{[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][3,Post comment 2:0,0,55]} {[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][3,Post comment 2:1,0,56]}Query:{[update Post set title=?, version=? where id=? and version=?][Blog Post no. 1,1,2,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][2,Blog Post comment 1:0,1,53,0]} Query:{[update Post set title=?, version=? where id=? and version=?][Blog Post no. 0,1,1,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][1,Blog Post comment 0:1,1,52,0]} Query:{[update Post set title=?, version=? where id=? and version=?][Blog Post no. 2,1,3,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][3,Blog Post comment 2:0,1,55,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][3,Blog Post comment 2:1,1,56,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][1,Blog Post comment 0:0,1,51,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][2,Blog Post comment 1:1,1,54,0]}

JDBC批處理只能針對一個表，因此，針對不同表的每個新DML語句都會終止當前的批處理并啟動一個新的。 因此，在使用SQL批處理時，不希望混合使用不同的表語句。

訂購說明

Hibernate可以使用以下配置選項對INSERT和UPDATE語句進行排序：

properties.put("hibernate.order_inserts", "true"); properties.put("hibernate.order_updates", "true");

盡管對Post和Comment INSERT語句進行了相應的批處理，但UPDATE語句仍單獨執行：

Query:{[insert into Post (title, version, id) values (?, ?, ?)][Post no. 0,0,1]} {[insert into Post (title, version, id) values (?, ?, ?)][Post no. 1,0,2]} {[insert into Post (title, version, id) values (?, ?, ?)][Post no. 2,0,3]} Query:{[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][1,Post comment 0:0,0,51]} {[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][1,Post comment 0:1,0,52]} {[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][2,Post comment 1:0,0,53]} {[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][2,Post comment 1:1,0,54]} {[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][3,Post comment 2:0,0,55]} {[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][3,Post comment 2:1,0,56]}Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][1,Blog Post comment 0:0,1,51,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][1,Blog Post comment 0:1,1,52,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][2,Blog Post comment 1:0,1,53,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][2,Blog Post comment 1:1,1,54,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][3,Blog Post comment 2:0,1,55,0]} Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][3,Blog Post comment 2:1,1,56,0]} Query:{[update Post set title=?, version=? where id=? and version=?][Blog Post no. 0,1,1,0]} Query:{[update Post set title=?, version=? where id=? and version=?][Blog Post no. 1,1,2,0]} Query:{[update Post set title=?, version=? where id=? and version=?][Blog Post no. 2,1,3,0]}

添加版本數據批處理支持

我們需要設置hibernate.jdbc.batch_versioned_data配置屬性，以啟用UPDATE批處理：

如果您的JDBC驅動程序從executeBatch（）返回正確的行數，則將此屬性設置為true。 通常可以安全地打開此選項。 然后，Hibernate將使用批處理的DML來自動版本化數據。 默認為false。

我們也將使用此屬性集重新運行測試：

properties.put("hibernate.jdbc.batch_versioned_data", "true");

現在， INSERT和UPDATE語句均已正確批處理：

Query:{[insert into Post (title, version, id) values (?, ?, ?)][Post no. 0,0,1]} {[insert into Post (title, version, id) values (?, ?, ?)][Post no. 1,0,2]} {[insert into Post (title, version, id) values (?, ?, ?)][Post no. 2,0,3]} Query:{[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][1,Post comment 0:0,0,51]} {[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][1,Post comment 0:1,0,52]} {[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][2,Post comment 1:0,0,53]} {[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][2,Post comment 1:1,0,54]} {[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][3,Post comment 2:0,0,55]} {[insert into Comment (post_id, review, version, id) values (?, ?, ?, ?)][3,Post comment 2:1,0,56]}Query:{[update Comment set post_id=?, review=?, version=? where id=? and version=?][1,Blog Post comment 0:0,1,51,0]} {[update Comment set post_id=?, review=?, version=? where id=? and version=?][1,Blog Post comment 0:1,1,52,0]} {[update Comment set post_id=?, review=?, version=? where id=? and version=?][2,Blog Post comment 1:0,1,53,0]} {[update Comment set post_id=?, review=?, version=? where id=? and version=?][2,Blog Post comment 1:1,1,54,0]} {[update Comment set post_id=?, review=?, version=? where id=? and version=?][3,Blog Post comment 2:0,1,55,0]} {[update Comment set post_id=?, review=?, version=? where id=? and version=?][3,Blog Post comment 2:1,1,56,0]} Query:{[update Post set title=?, version=? where id=? and version=?][Blog Post no. 0,1,1,0]} {[update Post set title=?, version=? where id=? and version=?][Blog Post no. 1,1,2,0]} {[update Post set title=?, version=? where id=? and version=?][Blog Post no. 2,1,3,0]}

基準測試

既然我們已經為JDBC批處理配置了Hibernate，我們就可以對語句分組的性能??提升進行基準測試。

• 測試用例使用與當前正在運行的JVM安裝在同一臺機器上的PostgreSQL數據庫
• 選擇了50的批量，并且每次測試迭代都會將語句計數增加一個數量級
• 所有持續時間均以毫秒表示

報表數量 無批次插入持續時間 無批次更新持續時間 批量插入時間 批量更新持續時間

30	218	178	191	144
300	311	327	208	217
3000	1047	1089	556	478
30000	5889	6032	2640	2301
300000	51785	57869	16052	20954

我們執行INSERT或UPDATE的行越多，從JDBC批處理中受益越多。 對于最寫的應用程序（例如企業級企業批處理程序 ），我們絕對應該啟用JDBC批處理，因為其性能優勢可能是驚人的 。

• 代碼可在GitHub上獲得 。

翻譯自: https://www.javacodegeeks.com/2015/03/how-to-batch-insert-and-update-statements-with-hibernate.html

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