Java 将ORACLE Flashback与QueryDSL结合使用
我们使用QueryDSL通过SpringBoot应用程序从Oracle数据库批量读取数据Java 将ORACLE Flashback与QueryDSL结合使用,java,sql,querydsl,flashback,Java,Sql,Querydsl,Flashback,我们使用QueryDSL通过SpringBoot应用程序从Oracle数据库批量读取数据 final QFps fps = QFps.fps; final SQLQuery<Tuple> query = queryFactory.select(fps.fpId, fps.fieldA, fps.fieldB) .from(fps)
final QFps fps = QFps.fps;
final SQLQuery<Tuple> query = queryFactory.select(fps.fpId, fps.fieldA, fps.fieldB)
.from(fps)
.where(fps.fpId.eq(fpId));
final String sql = query.getSQL().getSQL();
log.info("sql={}", sql);
return query.fetch();
这同样适用于左连接:
final QFps fps = QFps.fps;
final QHalt halt = QHalt.halt;
final SQLQuery<Tuple> query = queryFactory.select(fps.fpId, fps.fieldA, fps.fieldB, halt.fieldC)
.from(fps)
.leftJoin(halt).on(fps.fieldA.eq(halt.id))
.where(fps.fpId.eq(fpId));
final String sql = query.getSQL().getSQL();
log.info("sql={}", sql);
return query.fetch();
然而,由于我们需要查询特定时间点的数据,我们需要利用Oracle的Flashback功能。基本上,这需要在表名和别名之间添加以下SQL:
AS OF TIMESTAMP TO_TIMESTAMP('2021-01-26 14:48:23', 'YYYY-MM-DD HH24:MI:SS')
i、 e
我尝试使用.addFlag()
和.addJoinFlag()
命令在QueryDSL中实现此功能,但未成功
final QFps fps = QFps.fps;
final SQLQuery<Tuple> query = queryFactory.select(fps.fpId, fps.fieldA, fps.fieldB)
.from(fps)
.addFlag(Position.BEFORE_FILTER, getFlashbackString())
.where(fps.fpId.eq(fpId));
final String sql = query.getSQL().getSQL();
log.info("sql={}", sql);
return query.fetch();
具体来说,问题在于闪回字符串添加在别名之后,而不是表名和别名之间
使用联接时,情况会变得更糟:
final QFps fps = QFps.fps;
final QHalt halt = QHalt.halt;
final SQLQuery<Tuple> query = queryFactory.select(fps.fpId, fps.fieldA, fps.fieldB, halt.fieldC)
.from(fps)
.addFlag(Position.BEFORE_FILTER, getFlashbackString())
.leftJoin(halt).on(fps.fieldA.eq(halt.id))
.addJoinFlag(getFlashbackString())
.where(fps.fpId.eq(fpId));
final String sql = query.getSQL().getSQL();
log.info("sql={}", sql);
return query.fetch();
.addJoinFlag()
的结果添加在表名之前,而.addFlag()
的内容添加在where
之前,这并不奇怪
final QFps fps = QFps.fps;
final QHalt halt = QHalt.halt;
final SQLQuery<Tuple> query = queryFactory.select(fps.fpId, fps.fieldA, fps.fieldB, halt.fieldC)
.from(fps)
.addFlag(Position.BEFORE_FILTER, getFlashbackString())
.leftJoin(halt).on(fps.fieldA.eq(halt.id))
.addJoinFlag(getFlashbackString(), Position.BEFORE_CONDITION)
.where(fps.fpId.eq(fpId));
final String sql = query.getSQL().getSQL();
log.info("sql={}", sql);
return query.fetch();
这没什么好的
我已经尝试了各种可能的方法,但没有找到一种方法将要插入的字符串放置在正确的位置
我是否缺少在查询的某些位置注入SQL的另一种方法
如果做不到这一点,我可以使用QueryDSL生成SQL字符串,然后自己使用正则表达式修改它。有没有一种方法可以将这样的字符串传递给QueryDSL以便执行查询
整合接受的答案 Jan Willem Gmellig Meyling给出的答案很有效,我只想将其完全整合到我上面的样本中: 我创建了一个助手方法:
private static final String ADDITIONAL_FLASHBACK_EXPRESSION = "{0} AS OF TIMESTAMP TO_TIMESTAMP({1}, 'YYYY-MM-DD HH24:MI:SS') {2}";
private static final DateTimeFormatter FLASHBACK_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
public <T> Expression<String> getFlashbackExpresion(final Timestamp flashbackTimestamp, final RelationalPathBase<T> table) {
if (flashbackTimestamp == null) {
return Expressions.stringTemplate(WITHOUT_FLASHBACK_EXPRESSION, table, table);
}
final LocalDateTime timestamp = LocalDateTime.ofInstant(flashbackTimestamp.toInstant(), ZoneOffset.ofHours(0));
final String timestampString = timestamp.format(FLASHBACK_FORMATTER);
return Expressions.stringTemplate(ADDITIONAL_FLASHBACK_EXPRESSION, table, timestampString, table);
}
产生
select FPS.FP_ID, FPS.FIELD_A, FPS.FIELD_B, HALT.FIELD_C
from FPS AS OF TIMESTAMP TO_TIMESTAMP('2021-01-26 14:48:23', 'YYYY-MM-DD HH24:MI:SS') FPS
join HALT AS OF TIMESTAMP TO_TIMESTAMP('2021-01-26 14:48:23', 'YYYY-MM-DD HH24:MI:SS') HALT on FPS.FIELD_A = HALT.ID
where FPS.FP_ID = ?
这正是我想要的。尽管JoinFlags用于实现类似的功能,但正如您所注意到的,JoinFlags目前不能用于在路径表达式和别名之间插入标志。这实际上是因为连接别名嵌入在路径表达式中 将SQL片段插入生成的查询的另一种机制是通过
TemplateExpressions
。尽管不存在将TemplateExpressions
用作联接目标的API,但您可以通过基础查询元数据将任何表达式类型添加为联接:
//甚至为您将其参数化:)
表达式闪回=Expressions.stringTemplate(
“{0}从时间戳到_时间戳({1},'YYYY-MM-DD HH24:MI:SS')”,
停止
'2021-01-26 14:48:23');
查询来源(fps);
query.getMetadata().addJoin(JoinType.LEFTJOIN,flashback);
on(fps.fieldA.eq(halt.id));
如果您不喜欢上面代码段的语法,还有其他一些方法。您还可以看看我是如何在QueryDSL for JPA:上实现处理路径的。但是,这需要您在QueryDSL核心类中引入一个更改。谢谢,该代码段在连接中运行良好。我仍在尝试如何为
from()
语句实现同样的功能,但希望这能给我一个开始。啊,我刚刚发现我可以使用stringTemplate作为from()的输入,解决我所有的问题!
final QFps fps = QFps.fps;
final QHalt halt = QHalt.halt;
final SQLQuery<Tuple> query = queryFactory.select(fps.fpId, fps.fieldA, fps.fieldB, halt.fieldC)
.from(fps)
.addFlag(Position.BEFORE_FILTER, getFlashbackString())
.leftJoin(halt).on(fps.fieldA.eq(halt.id))
.addJoinFlag(getFlashbackString())
.where(fps.fpId.eq(fpId));
final String sql = query.getSQL().getSQL();
log.info("sql={}", sql);
return query.fetch();
select FPS.FP_ID, FPS.FIELD_A, FPS.FIELD_B, HALT.FIELD_C
from FPS FPS
join AS OF TIMESTAMP TO_TIMESTAMP('2021-01-26 14:48:23', 'YYYY-MM-DD HH24:MI:SS') HALT HALT on FPS.FIELD_A = HALT.ID AS OF TIMESTAMP TO_TIMESTAMP('2021-01-26 14:48:23', 'YYYY-MM-DD HH24:MI:SS')
where FPS.FP_ID = ?
final QFps fps = QFps.fps;
final QHalt halt = QHalt.halt;
final SQLQuery<Tuple> query = queryFactory.select(fps.fpId, fps.fieldA, fps.fieldB, halt.fieldC)
.from(fps)
.addFlag(Position.BEFORE_FILTER, getFlashbackString())
.leftJoin(halt).on(fps.fieldA.eq(halt.id))
.addJoinFlag(getFlashbackString(), Position.BEFORE_CONDITION)
.where(fps.fpId.eq(fpId));
final String sql = query.getSQL().getSQL();
log.info("sql={}", sql);
return query.fetch();
select FPS.FP_ID, FPS.FIELD_A, FPS.FIELD_B, HALT.FIELD_C
from FPS FPS
join HALT HALT AS OF TIMESTAMP TO_TIMESTAMP('2021-01-26 14:48:23', 'YYYY-MM-DD HH24:MI:SS') on FPS.FIELD_A = HALT.ID AS OF TIMESTAMP TO_TIMESTAMP('2021-01-26 14:48:23', 'YYYY-MM-DD HH24:MI:SS')
where FPS.FP_ID = ?
private static final String ADDITIONAL_FLASHBACK_EXPRESSION = "{0} AS OF TIMESTAMP TO_TIMESTAMP({1}, 'YYYY-MM-DD HH24:MI:SS') {2}";
private static final DateTimeFormatter FLASHBACK_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
public <T> Expression<String> getFlashbackExpresion(final Timestamp flashbackTimestamp, final RelationalPathBase<T> table) {
if (flashbackTimestamp == null) {
return Expressions.stringTemplate(WITHOUT_FLASHBACK_EXPRESSION, table, table);
}
final LocalDateTime timestamp = LocalDateTime.ofInstant(flashbackTimestamp.toInstant(), ZoneOffset.ofHours(0));
final String timestampString = timestamp.format(FLASHBACK_FORMATTER);
return Expressions.stringTemplate(ADDITIONAL_FLASHBACK_EXPRESSION, table, timestampString, table);
}
final Timestamp flashbackTimestamp = getFlashbackTimestamp();
final QFps fps = QFps.fps;
final QHalt halt = QHalt.halt;
final fpsFlashback = getFlashbackExpresion(flashbackTimestamp, fps);
final haltFlashback = getFlashbackExpresion(flashbackTimestamp, halt);
final SQLQuery<Tuple> query = queryFactory.select(fps.fpId, fps.fieldA, fps.fieldB, halt.fieldC);
query.from(fpsFlashback)
.getMetadata().addJoin(JointType.LEFTJOIN, haltFlashback);
query.on(fps.fieldA.eq(halt.id))
.where(fps.fpId.eq(fpId));
final String sql = query.getSQL().getSQL();
log.info("sql={}", sql);
return query.fetch();
select FPS.FP_ID, FPS.FIELD_A, FPS.FIELD_B, HALT.FIELD_C
from FPS AS OF TIMESTAMP TO_TIMESTAMP('2021-01-26 14:48:23', 'YYYY-MM-DD HH24:MI:SS') FPS
join HALT AS OF TIMESTAMP TO_TIMESTAMP('2021-01-26 14:48:23', 'YYYY-MM-DD HH24:MI:SS') HALT on FPS.FIELD_A = HALT.ID
where FPS.FP_ID = ?