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Allow the code and the DB to have different but compatible schemas.

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We check for compatibility by specifying a schema version and minimum
schema version in the code, storing them in the DB, and checking whether
the DB is too old for the code or vice versa.
This commit is contained in:
akwizgran
2014-02-04 19:51:41 +00:00
parent 597c907a42
commit 1ac8524dc2
3 changed files with 39 additions and 37 deletions
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64
briar-core/src/org/briarproject/db/JdbcDatabase.java
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@@ -38,7 +38,6 @@ import org.briarproject.api.TransportId;
import org.briarproject.api.TransportProperties;
import org.briarproject.api.db.DbClosedException;
import org.briarproject.api.db.DbException;
import org.briarproject.api.db.DbSchemaException;
import org.briarproject.api.db.MessageHeader;
import org.briarproject.api.messaging.Group;
import org.briarproject.api.messaging.GroupId;
@@ -61,7 +60,8 @@ import org.briarproject.api.transport.TemporarySecret;
*/
abstract class JdbcDatabase implements Database<Connection> {
private static final int SCHEMA_VERSION = 2;
private static final int SCHEMA_VERSION = 3;
private static final int MIN_SCHEMA_VERSION = 3;
private static final String CREATE_SETTINGS =
"CREATE TABLE settings"
@@ -372,11 +372,13 @@ abstract class JdbcDatabase implements Database<Connection> {
Connection txn = startTransaction();
try {
if(reopen) {
if(!checkSchemaVersion(txn))
throw new DbSchemaException();
if(!checkSchemaVersion(txn)) throw new DbException();
} else {
createTables(txn);
setSchemaVersion(txn);
String schemaVersion = String.valueOf(SCHEMA_VERSION);
setSetting(txn, "schemaVersion", schemaVersion);
String minSchemaVersion = String.valueOf(MIN_SCHEMA_VERSION);
setSetting(txn, "minSchemaVersion", minSchemaVersion);
}
commitTransaction(txn);
} catch(DbException e) {
@@ -386,27 +388,53 @@ abstract class JdbcDatabase implements Database<Connection> {
}
private boolean checkSchemaVersion(Connection txn) throws DbException {
try {
String value = getSetting(txn, "schemaVersion");
int schemaVersion = Integer.valueOf(value);
if(schemaVersion == SCHEMA_VERSION) return true;
if(schemaVersion < MIN_SCHEMA_VERSION) return false;
value = getSetting(txn, "minSchemaVersion");
int minSchemaVersion = Integer.valueOf(value);
return SCHEMA_VERSION >= minSchemaVersion;
} catch(NumberFormatException e) {
throw new DbException(e);
}
}
private String getSetting(Connection txn, String key) throws DbException {
PreparedStatement ps = null;
ResultSet rs = null;
String value;
try {
String sql = "SELECT value FROM settings WHERE key = ?";
ps = txn.prepareStatement(sql);
ps.setString(1, "schemaVersion");
ps.setString(1, key);
rs = ps.executeQuery();
if(!rs.next()) throw new DbStateException();
value = rs.getString(1);
String value = rs.getString(1);
if(rs.next()) throw new DbStateException();
rs.close();
ps.close();
return value;
} catch(SQLException e) {
tryToClose(rs);
tryToClose(ps);
throw new DbException(e);
}
}
private void setSetting(Connection txn, String key, String value)
throws DbException {
PreparedStatement ps = null;
try {
return Integer.valueOf(value) == SCHEMA_VERSION;
} catch(NumberFormatException e) {
String sql = "INSERT INTO settings (key, value) VALUES (?, ?)";
ps = txn.prepareStatement(sql);
ps.setString(1, key);
ps.setString(2, value);
int affected = ps.executeUpdate();
if(affected < 1) throw new DbStateException();
ps.close();
} catch(SQLException e) {
tryToClose(ps);
throw new DbException(e);
}
}
@@ -469,22 +497,6 @@ abstract class JdbcDatabase implements Database<Connection> {
return s;
}
private void setSchemaVersion(Connection txn) throws DbException {
PreparedStatement ps = null;
try {
String sql = "INSERT INTO settings (key, value) VALUES (?, ?)";
ps = txn.prepareStatement(sql);
ps.setString(1, "schemaVersion");
ps.setString(2, String.valueOf(SCHEMA_VERSION));
int affected = ps.executeUpdate();
if(affected != 1) throw new DbStateException();
ps.close();
} catch(SQLException e) {
tryToClose(ps);
throw new DbException(e);
}
}
public Connection startTransaction() throws DbException {
Connection txn = null;
synchronized(connections) {