pentaho/pentaho-kettle · error · KettleDatabaseException

Unable to prepare combi insert statement : + Const.CR +…

Error message

Unable to prepare combi insert statement :  + Const.CR + sqlStatement

What it means

combiInsert builds the INSERT statement for a new junk-dimension row and prepares a JDBC PreparedStatement. SQLException (or any other exception) during preparation is wrapped into a KettleDatabaseException 'Unable to prepare combi insert statement : <sql>'.

Solutions

Read the cause SQLException and the embedded SQL statement; run it manually against the DB to see the real error
Create/verify the junk dimension table and required columns
Grant INSERT privileges to the connection's DB user
Reconnect the database (retest connection metadata) if the session was dropped

Example fix

-- before: table missing
-- KettleDatabaseException: Unable to prepare combi insert statement
-- after: create the junk dimension table first
CREATE TABLE junk_dim (id BIGINT PRIMARY KEY, hashcode BIGINT, ...);

Defensive patterns

Strategy: retry

Validate before calling

Database db = new Database(parent, databaseMeta);
db.connect();
if (!db.checkTableExists(schemaTable)) {
  throw new IllegalStateException("Junk dimension table missing before insert: " + schemaTable);
}
db.disconnect();

Try / catch

try {
  trans.execute(null);
  trans.waitUntilFinished();
} catch (KettleDatabaseException e) {
  log.error("Combi insert prepare failed, SQL: " + e.getMessage(), e);
  // inspect cause for INSERT privilege or syntax errors before retrying
}

Prevention

Ensure the DB user has INSERT grants on the junk dimension
Create the dimension table before the transformation runs
Log and review the generated SQL statement on failure

When it happens

Trigger: data.db.getConnection().prepareStatement(stripCR(sqlStatement)) throws in combiInsert (called from lookupValues) — invalid SQL, missing table/columns, insufficient INSERT privilege, or a closed connection.

Common situations: Junk dimension table absent (never created); DB user without INSERT grant; datatype mismatch in the generated SQL; connection broken mid-transformation.

Understand the failure class

Background: "query failed", "%w: SQL error" — wrapped database query errors in Go libraries explained — this error's family across 3 libraries.

Related errors

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/53c3d06c5d2fc13d. Report an issue: GitHub.

Appendix: source

Thrown at plugins/core/impl/src/main/java/org/pentaho/di/trans/steps/combinationlookup/CombinationLookup.java:582

        }

        sql += " )";

        String sqlStatement = sql;
        try {
          debug = "First: prepare statement";
          if ( isAutoIncrement() && databaseMeta.supportsAutoGeneratedKeys() ) {
            logDetailed( "SQL with return keys: " + sqlStatement );
            data.prepStatementInsert =
              data.db.getConnection().prepareStatement(
                databaseMeta.stripCR( sqlStatement ), Statement.RETURN_GENERATED_KEYS );
          } else {
            logDetailed( "SQL without return keys: " + sqlStatement );
            data.prepStatementInsert =
              data.db.getConnection().prepareStatement( databaseMeta.stripCR( sqlStatement ) );
          }
        } catch ( SQLException ex ) {
          throw new KettleDatabaseException( "Unable to prepare combi insert statement : "
            + Const.CR + sqlStatement, ex );
        } catch ( Exception ex ) {
          throw new KettleDatabaseException( "Unable to prepare combi insert statement : "
            + Const.CR + sqlStatement, ex );
        }
      }

      debug = "Create new insert row rins";
      Object[] insertRow = new Object[ data.insertRowMeta.size() ];
      int insertIndex = 0;

      if ( !isAutoIncrement() ) {
        insertRow[ insertIndex ] = val_key;
        insertIndex++;
      }
      if ( meta.useHash() ) {
        insertRow[ insertIndex ] = val_crc;
        insertIndex++;

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