Hello:
When reading derby docs, I noticed that the function WwdUtils.wwdChk4Table in
Derby demos is implemented by executing an update on the table and then relying
on the exception mechanism to determine whether or not the table exists.
My approach was to execute DatabaseMetaData.getTables method (pls see
implementation below) and iterate through the resultset. I also wanted to
assure case insensitivity.
Which method is more preferable from the point of efficiency and database
operations (locks, etc).
This code might be executed frequently and by multiple threads.
Thank you,
Pavel.
public static boolean tableExists(final Connection connection, final String
tableName) throws SQLException {
try {
final DatabaseMetaData databaseMetaData = connection.getMetaData();
final ResultSet resultSet = databaseMetaData.getTables(null, null,
null, new String[]{"TABLE"});
try {
while (resultSet.next()) {
if
(resultSet.getString("TABLE_NAME").equalsIgnoreCase(tableName)) {
return true;
}
}
} finally {
connection.commit();
resultSet.close();
}
return false;
} catch (SQLException e) {
Statement statement = null;
try {
final Connection c =
Components.getMemoryDb().getConnection(true);
statement = c.createStatement();
final String select = "SELECT * FROM SYSCS_DIAG.LOCK_TABLE";
final ResultSet resultSet = statement.executeQuery(select);
final int cnt = resultSet.getMetaData().getColumnCount();
final StringBuilder builder = new StringBuilder("Results of \""
+ select + "\":");
while (resultSet.next()) {
builder.append("\n\t");
for (int i = 1; i <= cnt; i++) {
if (i > 1) {
builder.append(",");
}
builder.append(resultSet.getObject(i));
}
}
logger.info(builder.toString());
} finally {
if (statement != null) {
statement.close();
}
}
throw e;
}
}
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