Example usage for org.apache.hadoop.mapreduce.lib.db DBConfiguration getInputQuery

Introduction

In this page you can find the example usage for org.apache.hadoop.mapreduce.lib.db DBConfiguration getInputQuery.

Prototype

public String getInputQuery() 

Source Link

Usage

From source file:net.mooncloud.mapreduce.lib.db.OracleDBRecordReader.java

License:Apache License

/** Returns the query for selecting the records from an Oracle DB. */
protected String getSelectQuery() {
    StringBuilder query = new StringBuilder();
    DBConfiguration dbConf = getDBConf();
    String conditions = getConditions();
    String tableName = getTableName();
    String[] fieldNames = getFieldNames();

    // Oracle-specific codepath to use rownum instead of LIMIT/OFFSET.
    if (dbConf.getInputQuery() == null) {
        query.append("SELECT ");

        for (int i = 0; i < fieldNames.length; i++) {
            query.append(fieldNames[i]);
            if (i != fieldNames.length - 1) {
                query.append(", ");
            }//from  w  w w  . ja va2  s  .c om
        }

        query.append(" FROM ").append(tableName);
        if (conditions != null && conditions.length() > 0)
            query.append(" WHERE ").append(conditions);
        String orderBy = dbConf.getInputOrderBy();
        if (orderBy != null && orderBy.length() > 0) {
            query.append(" ORDER BY ").append(orderBy);
        }
    } else {
        // PREBUILT QUERY
        query.append(dbConf.getInputQuery());
    }

    try {
        DBInputFormat.DBInputSplit split = getSplit();
        if (split.getLength() > 0 && split.getStart() > 0) {
            String querystring = query.toString();

            query = new StringBuilder();
            query.append("SELECT * FROM (SELECT a.*,ROWNUM dbif_rno FROM ( ");
            query.append(querystring);
            query.append(" ) a WHERE rownum <= ").append(split.getStart());
            query.append(" + ").append(split.getLength());
            query.append(" ) WHERE dbif_rno >= ").append(split.getStart());
        }
    } catch (IOException ex) {
        // ignore, will not throw.
    }

    return query.toString();
}

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