介紹

JDBC長期以來一直為DML語句批處理提供支持。 默認(rèn)情況下，所有語句都一個(gè)接一個(gè)地發(fā)送，每個(gè)語句都在單獨(dú)的網(wǎng)絡(luò)往返中發(fā)送。 批處理使我們能夠一次性發(fā)送多個(gè)語句，從而節(jié)省了不必要的套接字流刷新。

Hibernate將數(shù)據(jù)庫語句隱藏在事務(wù)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(shù)據(jù)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(shí)間

我們將從以下實(shí)體模型開始：

該帖子與Comment實(shí)體具有一對多關(guān)聯(lián)：

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

或者測試場景同時(shí)發(fā)出INSERT和UPDATE語句，因此我們可以驗(yàn)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(shù)量的Post實(shí)體，每個(gè)實(shí)體包含兩個(gè)Comment 。 為了簡潔起見，我們將保留3個(gè)帖子和方言的默認(rèn)批處理大小：

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

默認(rèn)批處理支持

Hibernate不會(huì)隱式使用JDBC批處理，并且每個(gè)INSERT和UPDATE語句都是分別執(zhí)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(shè)置此屬性并重新運(yùn)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(gè)表，因此，針對不同表的每個(gè)新DML語句都會(huì)終止當(dāng)前的批處理并啟動(dòng)一個(gè)新的。 因此，在使用SQL批處理時(shí)，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(xiàng)對INSERT和UPDATE語句進(jìn)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(jìn)行了相應(yīng)的批處理，但UPDATE語句仍單獨(dú)執(zhí)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(shù)據(jù)批處理支持

我們需要設(shè)置hibernate.jdbc.batch_versioned_data配置屬性，以啟用UPDATE批處理：

如果您的JDBC驅(qū)動(dòng)程序從executeBatch（）返回正確的行數(shù)，則將此屬性設(shè)置為true。 通常可以安全地打開此選項(xiàng)。 然后，Hibernate將使用批處理的DML來自動(dòng)版本化數(shù)據(jù)。 默認(rèn)為false。

我們也將使用此屬性集重新運(yùn)行測試：

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

現(xiàn)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(zhǔn)測試

既然我們已經(jīng)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(jìn)行基準(zhǔn)測試。

• 測試用例使用與當(dāng)前正在運(yùn)行的JVM安裝在同一臺(tái)機(jī)器上的PostgreSQL數(shù)據(jù)庫
• 選擇了50的批量，并且每次測試迭代都會(huì)將語句計(jì)數(shù)增加一個(gè)數(shù)量級
• 所有持續(xù)時(shí)間均以毫秒表示

報(bào)表數(shù)量 無批次插入持續(xù)時(shí)間 無批次更新持續(xù)時(shí)間 批量插入時(shí)間 批量更新持續(xù)時(shí)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(zhí)行INSERT或UPDATE的行越多，從JDBC批處理中受益越多。 對于最寫的應(yīng)用程序（例如企業(yè)級企業(yè)批處理程序 ），我們絕對應(yīng)該啟用JDBC批處理，因?yàn)槠湫阅軆?yōu)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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