/**
* Initialize the lob storage.
*/
public void init() {
if (init) {
return;
}
synchronized (handler) {
//org.h2.engine.Database和org.h2.engine.SessionRemote等都实现了org.h2.store.DataHandler接口
//只有org.h2.engine.Database不返回null, 对应server端
//org.h2.engine.SessionRemote返回null，对应client端
conn = handler.getLobConnection();
init = true;
if (conn == null) {
return;
}
try {
Statement stat = conn.createStatement();
// stat.execute("SET UNDO_LOG 0");
// stat.execute("SET REDO_LOG_BINARY 0");
boolean create = true;
PreparedStatement prep = conn.prepareStatement(
"SELECT ZERO() FROM INFORMATION_SCHEMA.COLUMNS WHERE " +
"TABLE_SCHEMA=? AND TABLE_NAME=? AND COLUMN_NAME=?");
prep.setString(1, "INFORMATION_SCHEMA");
prep.setString(2, "LOB_MAP");
prep.setString(3, "POS");
ResultSet rs;
rs = prep.executeQuery();
if (rs.next()) {
prep = conn.prepareStatement(
"SELECT ZERO() FROM INFORMATION_SCHEMA.TABLES WHERE " +
"TABLE_SCHEMA=? AND TABLE_NAME=?");
prep.setString(1, "INFORMATION_SCHEMA");
prep.setString(2, "LOB_DATA");
rs = prep.executeQuery();
if (rs.next()) {
create = false;
}
}
if (create) {
stat.execute("CREATE CACHED TABLE IF NOT EXISTS " + LOBS +
"(ID BIGINT PRIMARY KEY, BYTE_COUNT BIGINT, TABLE INT) HIDDEN");
stat.execute("CREATE INDEX IF NOT EXISTS " +
"INFORMATION_SCHEMA.INDEX_LOB_TABLE ON " + LOBS + "(TABLE)");
stat.execute("CREATE CACHED TABLE IF NOT EXISTS " + LOB_MAP +
"(LOB BIGINT, SEQ INT, POS BIGINT, HASH INT, BLOCK BIGINT, PRIMARY KEY(LOB, SEQ)) HIDDEN");
// TODO the column name OFFSET was used in version 1.3.156,
// so this can be remove in a later version
stat.execute("ALTER TABLE " + LOB_MAP + " RENAME TO " + LOB_MAP + " HIDDEN");
stat.execute("ALTER TABLE " + LOB_MAP + " ADD IF NOT EXISTS POS BIGINT BEFORE HASH");
stat.execute("ALTER TABLE " + LOB_MAP + " DROP COLUMN IF EXISTS \"OFFSET\"");
stat.execute("CREATE INDEX IF NOT EXISTS " +
"INFORMATION_SCHEMA.INDEX_LOB_MAP_DATA_LOB ON " + LOB_MAP + "(BLOCK, LOB)");
stat.execute("CREATE CACHED TABLE IF NOT EXISTS " + LOB_DATA +
"(BLOCK BIGINT PRIMARY KEY, COMPRESSED INT, DATA BINARY) HIDDEN");
}
rs = stat.executeQuery("SELECT MAX(BLOCK) FROM " + LOB_DATA);
rs.next();
nextBlock = rs.getLong(1) + 1;
stat.close();
} catch (SQLException e) {
throw DbException.convert(e);
}
}
}