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Improve count and exists query projections.

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We now use COUNT(*) and SELECT 1 for count respective exists queries to enable database optimizers instead of using the key columns.

Closes #1647
This commit is contained in:
Mark Paluch
2023-11-06 10:35:05 +01:00
parent 5312731623
commit 9ffbfb6f99
3 changed files with 8 additions and 23 deletions
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21
spring-data-r2dbc/src/main/java/org/springframework/data/r2dbc/core/R2dbcEntityTemplate.java
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@@ -253,18 +253,11 @@ public class R2dbcEntityTemplate implements R2dbcEntityOperations, BeanFactoryAw
Mono<Long> doCount(Query query, Class<?> entityClass, SqlIdentifier tableName) {
RelationalPersistentEntity<?> entity = getRequiredEntity(entityClass);
StatementMapper statementMapper = dataAccessStrategy.getStatementMapper().forType(entityClass);
StatementMapper.SelectSpec selectSpec = statementMapper //
.createSelect(tableName) //
.doWithTable((table, spec) -> {
Expression countExpression = entity.hasIdProperty()
? table.column(entity.getRequiredIdProperty().getColumnName())
: Expressions.just("1");
return spec.withProjection(Functions.count(countExpression));
});
.withProjection(Functions.count(Expressions.just("*")));
Optional<CriteriaDefinition> criteria = query.getCriteria();
if (criteria.isPresent()) {
@@ -290,17 +283,9 @@ public class R2dbcEntityTemplate implements R2dbcEntityOperations, BeanFactoryAw
Mono<Boolean> doExists(Query query, Class<?> entityClass, SqlIdentifier tableName) {
RelationalPersistentEntity<?> entity = getRequiredEntity(entityClass);
StatementMapper statementMapper = dataAccessStrategy.getStatementMapper().forType(entityClass);
StatementMapper.SelectSpec selectSpec = statementMapper.createSelect(tableName).limit(1);
if (entity.hasIdProperty()) {
selectSpec = selectSpec //
.withProjection(entity.getRequiredIdProperty().getColumnName());
} else {
selectSpec = selectSpec.withProjection(Expressions.just("1"));
}
StatementMapper.SelectSpec selectSpec = statementMapper.createSelect(tableName).limit(1)
.withProjection(Expressions.just("1"));
Optional<CriteriaDefinition> criteria = query.getCriteria();
if (criteria.isPresent()) {

6
spring-data-r2dbc/src/test/java/org/springframework/data/r2dbc/core/R2dbcEntityTemplateUnitTests.java
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@@ -100,7 +100,7 @@ public class R2dbcEntityTemplateUnitTests {
StatementRecorder.RecordedStatement statement = recorder.getCreatedStatement(s -> s.startsWith("SELECT"));
assertThat(statement.getSql()).isEqualTo("SELECT COUNT(person.id) FROM person WHERE person.THE_NAME = $1");
assertThat(statement.getSql()).isEqualTo("SELECT COUNT(*) FROM person WHERE person.THE_NAME = $1");
assertThat(statement.getBindings()).hasSize(1).containsEntry(0, Parameter.from("Walter"));
}
@@ -141,7 +141,7 @@ public class R2dbcEntityTemplateUnitTests {
MockResult result = MockResult.builder().row(MockRow.builder().identified(0, Long.class, 1L).build()).build();
recorder.addStubbing(s -> s.startsWith("SELECT COUNT(1)"), result);
recorder.addStubbing(s -> s.startsWith("SELECT COUNT(*)"), result);
entityTemplate.select(WithoutId.class).count() //
.as(StepVerifier::create) //
@@ -165,7 +165,7 @@ public class R2dbcEntityTemplateUnitTests {
StatementRecorder.RecordedStatement statement = recorder.getCreatedStatement(s -> s.startsWith("SELECT"));
assertThat(statement.getSql()).isEqualTo("SELECT person.id FROM person WHERE person.THE_NAME = $1 LIMIT 1");
assertThat(statement.getSql()).isEqualTo("SELECT 1 FROM person WHERE person.THE_NAME = $1 LIMIT 1");
assertThat(statement.getBindings()).hasSize(1).containsEntry(0, Parameter.from("Walter"));
}

4
spring-data-r2dbc/src/test/java/org/springframework/data/r2dbc/core/ReactiveSelectOperationUnitTests.java
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@@ -216,7 +216,7 @@ public class ReactiveSelectOperationUnitTests {
StatementRecorder.RecordedStatement statement = recorder.getCreatedStatement(s -> s.startsWith("SELECT"));
assertThat(statement.getSql()).isEqualTo("SELECT person.id FROM person WHERE person.THE_NAME = $1 LIMIT 1");
assertThat(statement.getSql()).isEqualTo("SELECT 1 FROM person WHERE person.THE_NAME = $1 LIMIT 1");
}
@Test // gh-220
@@ -239,7 +239,7 @@ public class ReactiveSelectOperationUnitTests {
StatementRecorder.RecordedStatement statement = recorder.getCreatedStatement(s -> s.startsWith("SELECT"));
assertThat(statement.getSql()).isEqualTo("SELECT COUNT(person.id) FROM person WHERE person.THE_NAME = $1");
assertThat(statement.getSql()).isEqualTo("SELECT COUNT(*) FROM person WHERE person.THE_NAME = $1");
}
static class Person {