How to set the sequence to the last used id for all tables in Oracle

oracleoracle-11g-r2

I'm working on an open source elearning system called Moodle which usually uses MySql or Postgresql, but can also use MSSQL and Oracle.

A client wishes to use Oracle, which I have limited experience of. I've got a local install of Oracle 11g r2.

I used a script to transfer data from MySql into Oracle, including the ID to keep the references.

But now when creating a record I get the error message : ORA-00001: unique constraint (SCHEMANAME.TABLENAME_ID_PK) violated

I'm guessing the sequences weren't updated when I inserted the ID's?

Is there an easy way to update all the table sequences to the last ID number used + 1 in each table?

Unless it's something else?

UPDATE : I can use this to get the last number in the sequence

SELECT sequence_name, last_number
FROM dba_sequences
WHERE sequence_owner = 'SCHEMA_NAME'
AND sequence_name LIKE 'V_%'

The last_number column has values but it looks like they are lower than the last id used in the table.

UPDATE 2: Found some existing code in Moodle that resets the sequence, I had wrongly assumed the naming convention for the sequences was created by Oracle but its Moodle. Here is some Moodle/PHP code that will reset all the sequences:

$todb = moodle_database::get_driver_instance($dbtype, $dblibrary);
$todb->connect($dbhost, $dbuser, $dbpass, $dbname, $prefix, $dboptions);
$totables = $todb->get_tables(false);
$tomgr = $todb->get_manager();

foreach ($totables as $table) {
    mtrace($table);
    try {
        $tomgr->reset_sequence($table);
    } catch (moodle_exception $e) {
        // There are a couple of temporary tables without indexes.
        mtrace($e->getMessage());
        continue;
    }
}

UPDATE 3 : This is basically what the reset sequence function does

$value = (int)$this->mdb->get_field_sql('SELECT MAX(id) FROM {'.$tablename.'}');
$value++;

// Calculate a sequence name from the tablename.
$seqname = $this->getSequenceFromDB($xmldb_table);
if (!$seqname) {
    // Fallback, seqname not found, something is wrong. Inform and use the alternative getNameForObject() method
    $seqname = $this->getNameForObject($table, 'id', 'seq');
}

$this->mdb->execute("DROP SEQUENCE $seqname");
$this->mdb->execute("CREATE SEQUENCE $seqname START WITH $value INCREMENT BY 1 NOMAXVALUE CACHE $this->sequence_cache_size");

Best Answer

First you have to find out what the current sequence value is and then reset it. I would write a script which does the following tasks:

  1. Get the max value from the table
  2. update/recreate the sequence

The script could look like this:

declare
  maxval number;
begin
  select max(id) into maxval from <table_1>;
  execute immediate 'ALTER SEQUENCE <sequence_name_1> START WITH '|| maxval+1 ||';';

  select max(id) into maxval from <table_2>;
  execute immediate 'ALTER SEQUENCE <sequence_name_2> START WITH '|| maxval+1 ||';';
end;
/

I'm pretty sure there are better scripts but if you have to do this task frequently this might do the job without much development time.

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