Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

SQL Server: if possible, use OFFSET and FETCH instead of JDBC methods #300

Merged
merged 1 commit into from
Dec 14, 2018
Merged

SQL Server: if possible, use OFFSET and FETCH instead of JDBC methods #300

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
51 changes: 47 additions & 4 deletions ...pse.persistence.core/src/org/eclipse/persistence/platform/database/SQLServerPlatform.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -45,8 +45,8 @@
* @since TOPLink/Java 1.0
*/
public class SQLServerPlatform extends org.eclipse.persistence.platform.database.DatabasePlatform {
/** Support for sequence objects added in SQL Server 2012 */
private boolean supportsSequenceObjects;
/** Support for sequence objects and OFFSET FETCH NEXT added in SQL Server 2012 */
private boolean isVersion11OrHigher;
private boolean isConnectionDataInitialized;

public SQLServerPlatform(){
Expand All @@ -62,7 +62,7 @@ public void initializeConnectionData(Connection connection) throws SQLException
}
DatabaseMetaData dmd = connection.getMetaData();
int databaseVersion = dmd.getDatabaseMajorVersion();
supportsSequenceObjects = databaseVersion >= 11;
isVersion11OrHigher = databaseVersion >= 11;
isConnectionDataInitialized = true;
this.driverSupportsNationalCharacterVarying = Helper.compareVersions(dmd.getDriverVersion(), "4.0.0") >= 0;
}
Expand Down Expand Up @@ -690,7 +690,7 @@ public boolean supportsIdentity() {
*/
@Override
public boolean supportsSequenceObjects() {
return supportsSequenceObjects;
return isVersion11OrHigher;
}

/**
Expand Down Expand Up @@ -732,4 +732,47 @@ public void writeUpdateOriginalFromTempTableSql(Writer writer, DatabaseTable tab
writer.write(tempTableName);
writeAutoJoinWhereClause(writer, tableName, tempTableName, pkFields, this);
}

@Override
public void printSQLSelectStatement(DatabaseCall call, ExpressionSQLPrinter printer, SQLSelectStatement statement) {
ReadQuery query = statement.getQuery();
if (query == null || !isVersion11OrHigher || !shouldUseRownumFiltering()) {
super.printSQLSelectStatement(call, printer, statement);
return;
}

int max = Math.max(0, query.getMaxRows());
int first = Math.max(0, query.getFirstResult());

if (max == 0 && first == 0) {
super.printSQLSelectStatement(call, printer, statement);
return;
}

// OFFSET + FETCH NEXT requires ORDER BY, so add an ordering if there are none
// this SQL will satisfy the query parser without actually changing the ordering of the rows
List<Expression> orderBy = statement.getOrderByExpressions();
if (orderBy.isEmpty()) {
orderBy.add(statement.getBuilder().literal("ROW_NUMBER() OVER (ORDER BY (SELECT null))"));
}

// decide exact syntax to use, depending on whether a limit is specified (could just have an offset)
String offsetFetchSql;
List<?> offsetFetchArgs;
if (max == 0) {
offsetFetchSql = "? OFFSET ? ROWS";
offsetFetchArgs = Arrays.asList(first);
} else {
offsetFetchSql = "? OFFSET ? ROWS FETCH NEXT ? ROWS ONLY";
offsetFetchArgs = Arrays.asList(first, max - first);
}

// append to the last ORDER BY clause
orderBy.add(orderBy.remove(orderBy.size() - 1).sql(offsetFetchSql, offsetFetchArgs));

super.printSQLSelectStatement(call, printer, statement);

call.setIgnoreFirstRowSetting(true);
call.setIgnoreMaxResultsSetting(true);
}
}