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# 3 Using Oracle Big Data SQL for Data Access

This chapter describes how to use Oracle Big Data SQL to create external tables and access data from Hadoop data sources as well as Oracle NoSQL Database.

It also describes some of the changes that Oracle Big Data SQL makes on the Oracle Database server.

- Creating an Oracle External Table for Hive Data

- Creating an Oracle External Table for Oracle NoSQL Database

- Creating an Oracle External Table for Apache HBase

- Creating an Oracle External Table for HDFS Files

- About the SQL CREATE TABLE Statement

- About Data Type Conversions

- Querying External Tables

- About Oracle Big Data SQL on the Database Server (Oracle Exadata Machine or Other)

## 3.1 Creating an Oracle External Table for Hive Data

You can easily create an Oracle external table for data in Apache Hive. Because the metadata is available to Oracle Database, you can query the data dictionary for information about Hive tables. Then you can use a PL/SQL function to generate a basic SQL `CREATE TABLE EXTERNAL ORGANIZATION` statement. You can modify the statement before execution to customize the external table.

### 3.1.1 Obtaining Information About a Hive Table

The `DBMS_HADOOP` PL/SQL package contains a function named `CREATE_EXTDDL_FOR_HIVE`. It returns the data dictionary language (DDL) to create an external table for accessing a Hive table. This function requires you to provide basic information about the Hive table:

- Name of the Hadoop cluster

- Name of the Hive database

- Name of the Hive table

- Whether the Hive table is partitioned

You can obtain this information by querying the `ALL_HIVE_TABLES` data dictionary view. It displays information about all Hive tables that you can access from Oracle Database.

This example shows that the current user has access to an unpartitioned Hive table named `RATINGS_HIVE_TABLE` in the default database. A user named `JDOE` is the owner.

    SQL> SELECT cluster_id, database_name, owner, table_name, partitioned FROM all_hive_tables;
    CLUSTER_ID   DATABASE_NAME  OWNER    TABLE_NAME         PARTITIONED
    ------------ -------------- -------- ------------------ --------------
    hadoop1      default        jdoe     ratings_hive_table  UN-PARTITIONED

See Also:

"Static Data Dictionary Views for Hive"

### 3.1.2 Using the CREATE_EXTDDL_FOR_HIVE Function

With the information from the data dictionary, you can use the `CREATE_EXTDDL_FOR_HIVE` function of `DBMS_HADOOP`. This example specifies a database table name of `RATINGS_DB_TABLE` in the current schema. The function returns the text of the `CREATE TABLE` command in a local variable named `DDLout`, but does not execute it.

    DECLARE
       DDLout VARCHAR2(4000);
    BEGIN
       dbms_hadoop.create_extddl_for_hive(
          CLUSTER_ID=>'hadoop1',
          DB_NAME=>'default',
          HIVE_TABLE_NAME=>'ratings_hive_table',
          HIVE_PARTITION=>FALSE,
          TABLE_NAME=>'ratings_db_table',
          PERFORM_DDL=>FALSE,
          TEXT_OF_DDL=>DDLout
       );
       dbms_output.put_line(DDLout);
    END;
    /

When this procedure runs, the `PUT_LINE` function displays the `CREATE TABLE` command:

    CREATE TABLE ratings_db_table (
       c0 VARCHAR2(4000),
       c1 VARCHAR2(4000),
       c2 VARCHAR2(4000),
       c3 VARCHAR2(4000),
       c4 VARCHAR2(4000),
       c5 VARCHAR2(4000),
       c6 VARCHAR2(4000),
       c7 VARCHAR2(4000))
    ORGANIZATION EXTERNAL
       (TYPE ORACLE_HIVE DEFAULT DIRECTORY DEFAULT_DIR
       ACCESS PARAMETERS
          (
           com.oracle.bigdata.cluster=hadoop1
           com.oracle.bigdata.tablename=default.ratings_hive_table
          )
       ) PARALLEL 2 REJECT LIMIT UNLIMITED

You can capture this information in a SQL script, and use the access parameters to change the Oracle table name, the column names, and the data types as desired before executing it. You might also use access parameters to specify a date format mask.

The `ALL_HIVE_COLUMNS` view shows how the default column names and data types are derived. This example shows that the Hive column names are C0 to C7, and that the Hive `STRING` data type maps to `VARCHAR2(4000)`:

    SQL> SELECT table_name, column_name, hive_column_type, oracle_column_type FROM all_hive_columns;

    TABLE_NAME            COLUMN_NAME  HIVE_COLUMN_TYPE ORACLE_COLUMN_TYPE
    --------------------- ------------ ---------------- ------------------
    ratings_hive_table    c0           string           VARCHAR2(4000)
    ratings_hive_table    c1           string           VARCHAR2(4000)
    ratings_hive_table    c2           string           VARCHAR2(4000)
    ratings_hive_table    c3           string           VARCHAR2(4000)
    ratings_hive_table    c4           string           VARCHAR2(4000)
    ratings_hive_table    c5           string           VARCHAR2(4000)
    ratings_hive_table    c6           string           VARCHAR2(4000)
    ratings_hive_table    c7           string           VARCHAR2(4000)

    8 rows selected.

See Also:

"DBMS_HADOOP PL/SQL Package"

### 3.1.3 Developing a CREATE TABLE Statement for ORACLE_HIVE

You can choose between using `DBMS_HADOOP` and developing a `CREATE TABLE` statement from scratch. In either case, you may need to set some access parameters to modify the default behavior of `ORACLE_HIVE`.

#### 3.1.3.1 Using the Default ORACLE_HIVE Settings

The following statement creates an external table named `ORDER` to access Hive data:

    CREATE TABLE order (cust_num    VARCHAR2(10),
                        order_num   VARCHAR2(20),
                        description VARCHAR2(100),
                        order_total NUMBER (8,2))
       ORGANIZATION EXTERNAL (TYPE  oracle_hive);

Because no access parameters are set in the statement, the `ORACLE_HIVE` access driver uses the default settings to do the following:

- Connects to the default Hadoop cluster.

- Uses a Hive table named `order`. An error results if the Hive table does not have fields named `CUST_NUM`, `ORDER_NUM`, `DESCRIPTION`, and `ORDER_TOTAL`.

- Sets the value of a field to `NULL` if there is a conversion error, such as a `CUST_NUM` value longer than 10 bytes.

#### 3.1.3.2 Overriding the Default ORACLE_HIVE Settings

You can set properties in the `ACCESS PARAMETERS` clause of the external table clause, which override the default behavior of the access driver. The following clause includes the `com.oracle.bigdata.overflow` access parameter. When this clause is used in the previous example, it truncates the data for the `DESCRIPTION` column that is longer than 100 characters, instead of throwing an error:

    (TYPE oracle_hive
     ACCESS PARAMETERS (
        com.oracle.bigdata.overflow={"action:"truncate", "col":"DESCRIPTION""} ))

The next example sets most of the available parameters for `ORACLE_HIVE`:

    CREATE TABLE order (cust_num VARCHAR2(10),
                        order_num VARCHAR2(20),
                        order_date DATE,
                        item_cnt NUMBER,
                        description VARCHAR2(100),
                        order_total (NUMBER(8,2)) ORGANIZATION EXTERNAL
      (TYPE oracle_hive
         ACCESS PARAMETERS (
            com.oracle.bigdata.tablename:  order_db.order_summary
            com.oracle.bigdata.colmap:     {"col":"ITEM_CNT", \
                                            "field":"order_line_item_count"}
            com.oracle.bigdata.overflow:   {"action":"TRUNCATE", \
                                            "col":"DESCRIPTION"}
            com.oracle.bigdata.erroropt:   [{"action":"replace", \
                                             "value":"INVALID_NUM" , \
                                             "col":["CUST_NUM","ORDER_NUM"]} ,\
                                            {"action":"reject", \
                                             "col":"ORDER_TOTAL}
    ))

The parameters make the following changes in the way that the `ORACLE_HIVE` access driver locates the data and handles error conditions:

- `com.oracle.bigdata.tablename`: Handles differences in table names. `ORACLE_HIVE` looks for a Hive table named `ORDER_SUMMARY` in the `ORDER.DB` database.

- `com.oracle.bigdata.colmap`: Handles differences in column names. The Hive `ORDER_LINE_ITEM_COUNT` field maps to the Oracle `ITEM_CNT` column.

- `com.oracle.bigdata.overflow`: Truncates string data. Values longer than 100 characters for the `DESCRIPTION` column are truncated.

- `com.oracle.bigdata.erroropt`: Replaces bad data. Errors in the data for `CUST_NUM` or `ORDER_NUM` set the value to `INVALID_NUM`.

## 3.2 Creating an Oracle External Table for Oracle NoSQL Database

You can use the `ORACLE_HIVE` access driver to access data stored in Oracle NoSQL Database. However, you must first create a Hive external table that accesses the KVStore. Then you can create an external table in Oracle Database over it, similar to the process described in "Creating an Oracle External Table for Hive Data".

This section contains the following topics:

- Creating a Hive External Table for Oracle NoSQL Database

- Creating the Oracle Database Table for Oracle NoSQL Data

- About Column Data Type Mappings

- Example of Accessing Data in Oracle NoSQL Database

### 3.2.1 Creating a Hive External Table for Oracle NoSQL Database

To provide access to the data in Oracle NoSQL Database, you create a Hive external table over the Oracle NoSQL table. Oracle Big Data SQL provides a StorageHandler named `oracle.kv.hadoop.hive.table.TableStorageHandler` that enables Hive to read the Oracle NoSQL Database table format.

The following is the basic syntax of a Hive `CREATE TABLE` statement for a Hive external table over an Oracle NoSQL table:

    CREATE EXTERNAL TABLE tablename colname coltype[, colname coltype,...]
    STORED BY 'oracle.kv.hadoop.hive.table.TableStorageHandler'
    TBLPROPERTIES (
               "oracle.kv.kvstore" = "database",
       "oracle.kv.hosts" = "nosql_node1:port[, nosql_node2:port...]",
       "oracle.kv.hadoop.hosts" = "hadoop_node1[,hadoop_node2...]",
       "oracle.kv.tableName" = "table_name");

Hive CREATE TABLE Parameters

tablename

  The name of the Hive external table being created.

  This table name will be used in SQL queries issued in Oracle Database, so choose a name that is appropriate for users. The name of the external table that you create in Oracle Database must be identical to the name of this Hive table.

  Table, column, and field names are case insensitive in Oracle NoSQL Database, Apache Hive, and Oracle Database.

colname coltype

  The names and data types of the columns in the Hive external table. See Table 3-1 for the data type mappings between Oracle NoSQL Database and Hive.

Hive CREATE TABLE TBLPROPERTIES Clause

oracle.kv.kvstore

  The name of the KVStore. Only upper- and lowercase letters and digits are valid in the name.

oracle.kv.hosts

  A comma-delimited list of host names and port numbers in the Oracle NoSQL Database cluster. Each string has the format hostname:port. Enter multiple names to provide redundancy in the event that a host fails.

oracle.kv.hadoop.hosts

  A comma-delimited list of all host names in the Hadoop cluster with Oracle Big Data SQL enabled.

oracle.kv.tableName

  The name of the table in Oracle NoSQL Database that stores the data for this Hive external table.

See Also:

Apache Hive Language Manual DDL at

`https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL#LanguageManualDDL-Create/Drop/TruncateTable`

### 3.2.2 Creating the Oracle Database Table for Oracle NoSQL Data

Use the following syntax to create an external table in Oracle Database that can access the Oracle NoSQL data through a Hive external table:

    CREATE TABLE tablename(colname colType[, colname colType...])
      ORGANIZATION EXTERNAL
        (TYPE ORACLE_HIVE DEFAULT DIRECTORY directory
         ACCESS PARAMETERS
             (access parameters)
        )
        REJECT LIMIT UNLIMITED;

In this syntax, you identify the column names and data types. For more about this syntax, see "About the SQL CREATE TABLE Statement".

### 3.2.3 About Column Data Type Mappings

When Oracle Big Data SQL retrieves data from Oracle NoSQL Database, the data is converted twice to another data type:

- To a Hive data type when the data is read into the columns of the Hive external table.

- To an Oracle data type when the data is read into the columns of an Oracle Database external table.

Table 3-1 identifies the supported Oracle NoSQL data types and their mappings to Hive and Oracle Database data types. Oracle Big Data SQL does not support the Oracle NoSQL complex data types Array, Map, and Record.

Table 3-1 Oracle NoSQL Database Data Type Mappings

Oracle NoSQL Database Data Type | Apache Hive Data Type | Oracle Database Data Type
--- | --- | ---
String | STRING | VARCHAR2
Boolean | BOOLEAN | NUMBER1
Integer | INT | NUMBER
Long | INT | NUMBER
Double | DOUBLE | NUMBER(p,s)
Float | FLOAT | NUMBER(p,s)

### 3.2.4 Example of Accessing Data in Oracle NoSQL Database

This example uses the sample data provided with the Oracle NoSQL Database software:

- Creating the Oracle NoSQL Database Example Table

- Creating the Example Hive Table for vehicleTable

- Creating the Oracle Table for VEHICLES

#### 3.2.4.1 Creating the Oracle NoSQL Database Example Table

Verify that the following files reside in the `examples/hadoop/table` directory:

    create_vehicle_table.kvs
    CountTableRows.java
    LoadVehicleTable.java

This example runs on a Hadoop cluster node named some1node07 and uses a KVStore named SOME1KV.

To create and populate the sample table in Oracle NoSQL Database:

1. Open a connection to an Oracle NoSQL Database node on your Hadoop cluster.

2. Create a table named `vehicleTable`. The following example uses the `load` command to run the commands in `create_vehicle_table.kvs`:

       $ cd NOSQL_HOME
       $ java -jar lib/kvcli.jar -host some1node07 -port 5000 \
         load -file examples/hadoop/table/create_vehicle_table.kvs

3. Compile `LoadVehicleTable.java`:

       $ javac -cp examples:lib/kvclient.jar examples/hadoop/table/LoadVehicleTable.java

4. Execute the `LoadVehicleTable` class to populate the table:

       $ java -cp examples:lib/kvclient.jar hadoop.table.LoadVehicleTable -host some1node07 -port 5000 -store SOME1KV
       {"type":"auto","make":"Chrysler","model":"PTCruiser","class":"4WheelDrive","colo
       r":"white","price":20743.240234375,"count":30}
       {"type":"suv","make":"Ford","model":"Escape","class":"FrontWheelDrive","color":"
            .
            .
            .
       10 new records added

The `vehicleTable` table contains the following fields:

Field Name | Data Type
--- | ---
type | STRING
make | STRING
model | STRING
class | STRING
color | STRING
price | DOUBLE
count | INTEGER

#### 3.2.4.2 Creating the Example Hive Table for vehicleTable

The following example creates a Hive table named `VEHICLES` that accesses `vehicleTable` in the SOME1KV KVStore. In this example, the system is configured with a Hadoop cluster in the first six servers (some1node01 to some1node06) and an Oracle NoSQL Database cluster in the next three servers (some1node07 to some1node09).

    CREATE EXTERNAL TABLE IF NOT EXISTS vehicles
       (type STRING,
        make STRING,
        model STRING,
        class STRING,
        color STRING,
        price DOUBLE,
        count INT)
    COMMENT 'Accesses data in vehicleTable in the SOME1KV KVStore'
    STORED BY 'oracle.kv.hadoop.hive.table.TableStorageHandler'
    TBLPROPERTIES
      ("oracle.kv.kvstore" = "SOME1KV",
       "oracle.kv.hosts" = "some1node07.example.com:5000,some1node08.example.com:5000",
       "oracle.kv.hadoop.hosts" = "some1node01.example.com,some1node02.example.com,some1node03.example.com,some1node04.example.com,some1node05.example.com,some1node06.example.com",
       "oracle.kv.tableName" = "vehicleTable");

The `DESCRIBE` command lists the columns in the `VEHICLES` table:

    hive> DESCRIBE vehicles;
    OK
    type                    string                  from deserializer
    make                    string                  from deserializer
    model                   string                  from deserializer
    class                   string                  from deserializer
    color                   string                  from deserializer
    price                   double                  from deserializer
    count                   int                     from deserializer

A query against the Hive `VEHICLES` table returns data from the Oracle NoSQL `vehicleTable` table:

    hive> SELECT make, model, class
          FROM vehicletable
          WHERE type='truck' AND color='red'
          ORDER BY make, model;
    Total MapReduce jobs = 1
    Launching Job 1 out of 1
    Number of reduce tasks determined at compile time: 1
         .
         .
         .
    Chrysler       Ram1500         RearWheelDrive
    Chrysler       Ram2500         FrontWheelDrive
    Ford           F150            FrontWheelDrive
    Ford           F250            RearWheelDrive
    Ford           F250            AllWheelDrive
    Ford           F350            RearWheelDrive
    GM             Sierra          AllWheelDrive
    GM             Silverado1500   RearWheelDrive
    GM             Silverado1500   AllWheelDrive

#### 3.2.4.3 Creating the Oracle Table for VEHICLES

After you create the Hive table, the metadata is available in the Oracle Database static data dictionary views. The following SQL `SELECT` statement returns information about the Hive table created in the previous topic:

    SQL> SELECT table_name, column_name, hive_column_type
         FROM all_hive_columns
         WHERE table_name='vehicles';
    TABLE_NAME      COLUMN_NAME  HIVE_COLUMN_TYPE
    --------------- ------------ ----------------
    vehicles        type         string
    vehicles        make         string
    vehicles        model        string
    vehicles        class        string
    vehicles        color        string
    vehicles        price        double
    vehicles        count        int

The next SQL `CREATE TABLE` statement generates an external table named `VEHICLES` over the Hive `VEHICLES` table, using the `ORACLE_HIVE` access driver. The name of the table in Oracle Database must be identical to the name of the table in Hive. However, both Oracle NoSQL Database and Oracle Database are case insensitive.

    CREATE TABLE vehicles
      (type  VARCHAR2(10), make  VARCHAR2(12), model VARCHAR2(20),
       class VARCHAR2(40), color VARCHAR2(20), price NUMBER(8,2),
       count NUMBER)
      ORGANIZATION EXTERNAL
        (TYPE ORACLE_HIVE DEFAULT DIRECTORY DEFAULT_DIR
           ACCESS PARAMETERS
             (com.oracle.bigdata.debug=true com.oracle.bigdata.log.opt=normal))
        REJECT LIMIT UNLIMITED;

This SQL `SELECT` statement retrieves all rows for red trucks from `vehicleTable` in Oracle NoSQL Database:

    SQL> SELECT make, model, class
         FROM vehicles
         WHERE type='truck' AND color='red'
         ORDER BY make, model;
    MAKE         MODEL                CLASS
    ------------ -------------------- ---------------------
    Chrysler     Ram1500              RearWheelDrive
    Chrysler     Ram2500              FrontWheelDrive
    Ford         F150                 FrontWheelDrive
    Ford         F250                 AllWheelDrive
    Ford         F250                 RearWheelDrive
    Ford         F350                 RearWheelDrive
    GM           Sierra               AllWheelDrive
    GM           Silverado1500        RearWheelDrive
    GM           Silverado1500        4WheelDrive
    GM           Silverado1500        AllWheelDrive

## 3.3 Creating an Oracle External Table for Apache HBase

You can also use the `ORACLE_HIVE` access driver to access data stored in Apache HBase. However, you must first create a Hive external table that accesses the HBase table. Then you can create an external table in Oracle Database over it. The basic steps are the same as those described in "Creating an Oracle External Table for Oracle NoSQL Database".

### 3.3.1 Creating a Hive External Table for HBase

To provide access to the data in an HBase table, you create a Hive external table over it. Apache provides a storage handler and a SerDe that enable Hive to read the HBase table format.

The following is the basic syntax of a Hive `CREATE TABLE` statement for an external table over an HBase table:

    CREATE EXTERNAL TABLE tablename colname coltype[, colname coltype,...]
    ROW FORMAT
       SERDE 'org.apache.hadoop.hive.hbase.HBaseSerDe'
    STORED BY 'org.apache.hadoop.hive.hbase.HBaseStorageHandler'
    WITH SERDEPROPERTIES (
       'serialization.format'='1',
       'hbase.columns.mapping'=':key,value:key,value:

See Also:

- Apache Hive Language Manual DDL at

  `https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL#LanguageManualDDL-Create/Drop/TruncateTable`

- Hive HBase Integration at

  `https://cwiki.apache.org/confluence/display/Hive/HBaseIntegration#HBaseIntegration-StorageHandlers`

- `Class HBaseSerDe` in the Hive API reference at

  `http://hive.apache.org/javadocs/r0.13.1/api/hbase-handler/index.html`

### 3.3.2 Creating the Oracle Database Table for HBase

Use the following syntax to create an external table in Oracle Database that can access the HBase data through a Hive external table:

    CREATE TABLE tablename(colname colType[, colname colType...])
      ORGANIZATION EXTERNAL
        (TYPE ORACLE_HIVE DEFAULT DIRECTORY DEFAULT_DIR
         ACCESS PARAMETERS
             (access parameters)
        )
        REJECT LIMIT UNLIMITED;

In this syntax, you identify the column names and data types. To specify the access parameters, see "About the SQL CREATE TABLE Statement".

## 3.4 Creating an Oracle External Table for HDFS Files

The `ORACLE_HDFS` access driver enables you to access many types of data that are stored in HDFS, but which do not have Hive metadata. You can define the record format of text data, or you can specify a SerDe for a particular data format.

You must create the external table for HDFS files manually, and provide all the information the access driver needs to locate the data, and parse the records and fields. The following are some examples of `CREATE TABLE ORGANIZATION EXTERNAL` statements.

### 3.4.1 Using the Default Access Parameters with ORACLE_HDFS

The following statement creates a table named `ORDER` to access the data in all files stored in the `/usr/cust/summary` directory in HDFS:

    CREATE TABLE ORDER (cust_num VARCHAR2(10),
                        order_num VARCHAR2(20),
                        order_total NUMBER (8,2))
      ORGANIZATION EXTERNAL
      ( TYPE oracle_hdfs
        DEFAULT DIRECTORY DEFAULT_DIR
      )
      LOCATION ('hdfs:/usr/cust/summary/*');

Because no access parameters are set in the statement, the `ORACLE_HDFS` access driver uses the default settings to do the following:

- Connects to the default Hadoop cluster.

- Reads the files as delimited text, and the fields as type `STRING`.

- Assumes that the number of fields in the HDFS files match the number of columns (three in this example).

- Assumes the fields are in the same order as the columns, so that `CUST_NUM` data is in the first field, `ORDER_NUM` data is in the second field, and `ORDER_TOTAL` data is in the third field.

- Rejects any records in which the value causes a data conversion error: If the value for `CUST_NUM` exceeds 10 characters, the value for `ORDER_NUM` exceeds 20 characters, or the value of `ORDER_TOTAL` cannot be converted to `NUMBER`.

### 3.4.2 Overriding the Default ORACLE_HDFS Settings

You can use many of the same access parameters with `ORACLE_HDFS` as `ORACLE_HIVE`.

#### 3.4.2.1 Accessing a Delimited Text File

The following example is equivalent to the one shown in "Overriding the Default ORACLE_HIVE Settings". The external table access a delimited text file stored in HDFS.

    CREATE TABLE order (cust_num VARCHAR2(10),
                        order_num VARCHAR2(20),
                        order_date DATE,
                        item_cnt NUMBER,
                        description VARCHAR2(100),
                        order_total NUMBER(8,2))
       ORGANIZATION EXTERNAL
       (
         TYPE oracle_hdfs
         DEFAULT DIRECTORY DEFAULT_DIR
               ACCESS PARAMETERS
                     (
            com.oracle.bigdata.colmap: {"col":"item_cnt", "field":"order_line_item_count"}
            com.oracle.bigdata.overflow: {"action":"TRUNCATE", "col":"DESCRIPTION"}
            com.oracle.bigdata.erroropt: [{"action":"replace", \
                                             "value":"INVALID NUM", \
                                             "col":["CUST_NUM","ORDER_NUM"]} , \
                                             {"action":"reject", "col":"ORDER_TOTAL}]
         )
     LOCATION ('hdfs:/usr/cust/summary/*'));

The parameters make the following changes in the way that the `ORACLE_HDFS` access driver locates the data and handles error conditions:

- `com.oracle.bigdata.colmap`: Handles differences in column names. `ORDER_LINE_ITEM_COUNT` in the HDFS files matches the `ITEM_CNT` column in the external table.

- `com.oracle.bigdata.overflow`: Truncates string data. Values longer than 100 characters for the `DESCRIPTION` column are truncated.

- `com.oracle.bigdata.erroropt`: Replaces bad data. Errors in the data for `CUST_NUM` or `ORDER_NUM` set the value to `INVALID_NUM`.

#### 3.4.2.2 Accessing Avro Container Files

The next example uses a SerDe to access Avro container files.

    CREATE TABLE order (cust_num VARCHAR2(10),
                        order_num VARCHAR2(20),
                        order_date DATE,
                        item_cnt NUMBER,
                        description VARCHAR2(100),
                        order_total NUMBER(8,2))
       ORGANIZATION EXTERNAL
       (
          TYPE oracle_hdfs
          DEFAULT DIRECTORY DEFAULT_DIR
          ACCESS PARAMETERS (
             com.oracle.bigdata.rowformat: \
             SERDE 'org.apache.hadoop.hive.serde2.avro.AvroSerDe'
             com.oracle.bigdata.fileformat: \
             INPUTFORMAT 'org.apache.hadoop.hive.ql.io.avro.AvroContainerInputFormat'\
             OUTPUTFORMAT 'org.apache.hadoop.hive.ql.io.avro.AvroContainerOutputFormat'
             com.oracle.bigdata.colmap: {  "col":"item_cnt", \
                     "field":"order_line_item_count"}
             com.oracle.bigdata.overflow: {"action":"TRUNCATE", \
                      "col":"DESCRIPTION"}
          )
          LOCATION ('hdfs:/usr/cust/summary/*'));

The access parameters provide the following information to the `ORACLE_HDFS` access driver:

- `com.oracle.bigdata.rowformat`: Identifies the SerDe that the access driver needs to use to parse the records and fields. The files are not in delimited text format.

- `com.oracle.bigdata.fileformat`: Identifies the Java classes that can extract records and output them in the desired format.

- `com.oracle.bigdata.colmap`: Handles differences in column names. `ORACLE_HDFS` matches `ORDER_LINE_ITEM_COUNT` in the HDFS files with the `ITEM_CNT` column in the external table.

- `com.oracle.bigdata.overflow`: Truncates string data. Values longer than 100 characters for the `DESCRIPTION` column are truncated.

## 3.5 About the SQL CREATE TABLE Statement

The SQL `CREATE TABLE` statement has a clause specifically for creating external tables. The information that you provide in this clause enables the access driver to read data from an external source and prepare the data for the external table.

### 3.5.1 Basic Syntax

The following is the basic syntax of the `CREATE TABLE` statement for external tables:

    CREATE TABLE table_name (column_name datatype,
                             column_name datatype[,...])
       ORGANIZATION EXTERNAL (external_table_clause);

You specify the column names and data types the same as for any other table. `ORGANIZATION EXTERNAL` identifies the table as an external table.

The external_table_clause identifies the access driver and provides the information that it needs to load the data. See "About the External Table Clause".

### 3.5.2 About the External Table Clause

`CREATE TABLE ORGANIZATION EXTERNAL` takes the external_table_clause as its argument. It has the following subclauses:

- TYPE Clause

- DEFAULT DIRECTORY Clause

- LOCATION Clause

- REJECT LIMIT Clause

- ORACLE_HIVE Access Parameters

See Also:

Oracle Database SQL Language Reference for the external_table_clause

#### 3.5.2.1 TYPE Clause

The `TYPE` clause identifies the access driver. The type of access driver determines how the other parts of the external table definition are interpreted.

Specify one of the following values for Oracle Big Data SQL:

- `ORACLE_HDFS`: Accesses files in an HDFS directory.

- `ORACLE_HIVE`: Accesses a Hive table.

Note:

The `ORACLE_DATAPUMP` and `ORACLE_LOADER` access drivers are not associated with Oracle Big Data SQL.

#### 3.5.2.2 DEFAULT DIRECTORY Clause

The `DEFAULT DIRECTORY` clause identifies an Oracle Database directory object. The directory object identifies an operating system directory with files that the external table reads and writes.

`ORACLE_HDFS` and `ORACLE_HIVE` use the default directory solely to write log files on the Oracle Database system.

#### 3.5.2.3 LOCATION Clause

The `LOCATION` clause identifies the data source.

#### 3.5.2.4 ORACLE_HDFS LOCATION Clause

The `LOCATION` clause for `ORACLE_HDFS` contains a comma-separated list of file locations. The files must reside in the HDFS file system on the default cluster.

A location can be any of the following:

- A fully qualified HDFS name, such as `/user/hive/warehouse/hive_seed/hive_types`. `ORACLE_HDFS` uses all files in the directory.

- A fully qualified HDFS file name, such as `/user/hive/warehouse/hive_seed/hive_types/hive_types.csv`

- A URL for an HDFS file or a set of files, such as `hdfs:/user/hive/warehouse/hive_seed/hive_types/*`. Just a directory name is invalid.

The file names can contain any pattern-matching character described in Table 3-2.

Table 3-2 Pattern-Matching Characters

Character | Description
--- | ---
? | Matches any one character
* | Matches zero or more characters
[abc] | Matches one character in the set {a, b, c}
[a-b] | Matches one character in the range {a...b}. The character must be less than or equal to b.
[^a] | Matches one character that is not in the character set or range {a}. The carat (^) must immediately follow the left bracket, with no spaces.
\c | Removes any special meaning of c. The backslash is the escape character.
{ab\,cd} | Matches a string from the set {ab, cd}. The escape character (\) removes the meaning of the comma as a path separator.
{ab\,c{de\,fh} | Matches a string from the set {ab, cde, cfh}. The escape character (\) removes the meaning of the comma as a path separator.

#### 3.5.2.5 ORACLE_HIVE LOCATION Clause

Do not specify the `LOCATION` clause for `ORACLE_HIVE`; it raises an error. The data is stored in Hive, and the access parameters and the metadata store provide the necessary information.

#### 3.5.2.6 REJECT LIMIT Clause

Limits the number of conversion errors permitted during a query of the external table before Oracle Database stops the query and returns an error.

Any processing error that causes a row to be rejected counts against the limit. The reject limit applies individually to each parallel query (PQ) process. It is not the total of all rejected rows for all PQ processes.

#### 3.5.2.7 ACCESS PARAMETERS Clause

The `ACCESS PARAMETERS` clause provides information that the access driver needs to load the data correctly into the external table. See "CREATE TABLE ACCESS PARAMETERS Clause".

## 3.6 About Data Type Conversions

When the access driver loads data into an external table, it verifies that the Hive data can be converted to the data type of the target column. If they are incompatible, then the access driver returns an error. Otherwise, it makes the appropriate data conversion.

Hive typically provides a table abstraction layer over data stored elsewhere, such as in HDFS files. Hive uses a serializer/deserializer (SerDe) to convert the data as needed from its stored format into a Hive data type. The access driver then converts the data from its Hive data type to an Oracle data type. For example, if a Hive table over a text file has a `BIGINT` column, then the SerDe converts the data from text to `BIGINT`. The access driver then converts the data from `BIGINT` (a Hive data type) to `NUMBER` (an Oracle data type).

Performance is better when one data type conversion is performed instead of two. The data types for the fields in the HDFS files should therefore indicate the data that is actually stored on disk. For example, JSON is a clear text format, therefore all data in a JSON file is text. If the Hive type for a field is `DATE`, then the SerDe converts the data from string (in the data file) to a Hive date. Then the access driver converts the data from a Hive date to an Oracle date. However, if the Hive type for the field is string, then the SerDe does not perform a conversion, and the access driver converts the data from string to an oracle date. Queries against the external table are faster in the second example, because the access driver performs the only data conversion.

Table 3-3 identifies the data type conversions that `ORACLE_HIVE` can make when loading data into an external table.

Table 3-3 Supported Hive to Oracle Data Type Conversions

Hive Data Type | VARCHAR2, CHAR, NCHAR2, NCHAR, CLOB | NUMBER, FLOAT, BINARY_NUMBER, BINARY_FLOAT | BLOB | RAW | DATE, TIMESTAMP, TIMESTAMP WITH TZ, TIMESTAMP WITH LOCAL TZ | INTERVAL YEAR TO MONTH, INTERVAL DAY TO SECOND
--- | --- | --- | --- | --- | --- | ---
INT SMALLINT TINYINT BIGINT | yes | yes | yes | yes | no | no
DOUBLE FLOAT | yes | yes | yes | yes | no | no
DECIMAL | yes | yes | no | no | no | no
BOOLEAN | yes2 | yes | yes3 | yes | no | no
BINARY | yes | no | yes | yes | no | no
STRING | yes | yes | yes | yes | yes | yes
TIMESTAMP | yes | no | no | no | yes | no
STRUCT ARRAY UNIONTYPE MAP | yes | no | no | no | no | no

## 3.7 Querying External Tables

Users can query external tables using the SQL `SELECT` statement, the same as they query any other table.

### 3.7.1 Granting User Access

Users who query the data on a Hadoop cluster must have `READ` access in Oracle Database to the external table and to the database directory object that points to the cluster directory. See "About the Cluster Directory".

### 3.7.2 About Error Handling

By default, a query returns no data if an error occurs while the value of a column is calculated. Processing continues after most errors, particularly those thrown while the column values are calculated.

Use the `com.oracle.bigdata.erroropt` parameter to determine how errors are handled.

### 3.7.3 About the Log Files

You can use these access parameters to customize the log files:

- `com.oracle.bigdata.log.exec`

- `com.oracle.bigdata.log.qc`

## 3.8 About Oracle Big Data SQL on the Database Server (Oracle Exadata Machine or Other)

This section explains the changes that the Oracle Big Data SQL installation makes to the Oracle Database system (which may or may not be an Oracle Exadata Machine).

The section contains the following topics:

- About the Common Directory

- Common Configuration Properties

- About the Cluster Directory

### 3.8.1 About the Common Directory

The directory `common` directory contains configuration information that is common to all Hadoop clusters. This directory is located on the Oracle Database system under the Oracle `home` directory. The `oracle` file system user (or whichever user owns the Oracle Database instance) owns the common directory. A database directory named `ORACLE_BIGDATA_CONFIG` points to `common`.

### 3.8.2 Common Configuration Properties

The installation store these files in the `common` directory under `/home/oracle` :

- `bigdata.properties`

- `bigdata-log4j.properties`

The Oracle DBA can edit these configuration files as necessary.

#### 3.8.2.1 bigdata.properties

The `bigdata.properties` file in the common directory contains property-value pairs that define the Java class paths and native library paths required for accessing data in HDFS.

These properties must be set:

- `bigdata.cluster.default`

- `java.classpath.hadoop`

- `java.classpath.hive`

- `java.classpath.oracle`

The following list describes all properties permitted in `bigdata.properties`.

bigdata.properties

bigdata.cluster.default | The name of the default Hadoop cluster. The access driver uses this name when the access parameters do not specify a cluster. Required. Changing the default cluster name might break external tables that were created previously without an explicit cluster name.
bigdata.cluster.list | A comma-separated list of Hadoop cluster names. Optional.
java.classpath.hadoop | The Hadoop class path. Required.
java.classpath.hive | The Hive class path. Required.
java.classpath.oracle | The path to the Oracle JXAD Java JAR file. Required.
java.classpath.user | The path to user JAR files. Optional.
java.libjvm.file | The full file path to the JVM shared library (such as `libjvm.so`). Required.
java.options | A comma-separated list of options to pass to the JVM. Optional. This example sets the maximum heap size to 2 GB, and verbose logging for Java Native Interface (JNI) calls:
    Xmx2048m,-verbose=jni
LD_LIBRARY_PATH | A colon separated (:) list of directory paths to search for the Hadoop native libraries. Recommended. If you set this option, then do not set java.library path in `java.options`.

Example 3-1 shows a sample `bigdata.properties` file.

Example 3-1 Sample bigdata.properties File

    # bigdata.properties
    #
    # Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
    #
    #    NAME
    #      bigdata.properties - Big Data Properties File
    #
    #    DESCRIPTION
    #      Properties file containing parameters for allowing access to Big Data
    #      Fixed value properties can be added here
    #

    java.libjvm.file=$ORACLE_HOME/jdk/jre/lib/amd64/server/libjvm.so
    java.classpath.oracle=$ORACLE_HOME/hadoopcore/jlib/*:$ORACLE_HOME/hadoop/jlib/hver-2/*:$ORACLE_HOME/dbjava/lib/*
    java.classpath.hadoop=$HADOOP_HOME/*:$HADOOP_HOME/lib/*
    java.classpath.hive=$HIVE_HOME/lib/*
    LD_LIBRARY_PATH=$ORACLE_HOME/jdk/jre/lib
    bigdata.cluster.default=hadoop_cl_1

#### 3.8.2.2 bigdata-log4j.properties

The `bigdata-log4j.properties` file in the common directory defines the logging behavior of queries against external tables in the Java code. Any `log4j` properties are allowed in this file.

Example 3-2 shows a sample `bigdata-log4j.properties` file with the relevant `log4j` properties.

Example 3-2 Sample bigdata-log4j.properties File

    # bigdata-log4j.properties
    #
    # Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
    #
    #    NAME
    #      bigdata-log4j.properties - Big Data Logging Properties File
    #
    #    DESCRIPTION
    #      Properties file containing logging parameters for Big Data
    #      Fixed value properties can be added here

    bigsql.rootlogger=INFO,console
    log4j.rootlogger=DEBUG, file
    log4j.appender.console=org.apache.log4j.ConsoleAppender
    log4j.appender.console.target=System.err
    log4j.appender.console.layout=org.apache.log4j.PatternLayout
    log4j.appender.console.layout.ConversionPattern=%d{yy/MM/dd HH:mm:ss} %p %c{2}: %m%n
    log4j.appender.file=org.apache.log4j.RollingFileAppender
    log4j.appender.file.layout=org.apache.log4j.PatternLayout
    log4j.appender.file.layout.ConversionPattern=%d{yy/MM/dd HH:mm:ss} %p %c{2}: %m%n
    log4j.logger.oracle.hadoop.sql=ALL, file

    bigsql.log.dir=.
    bigsql.log.file=bigsql.log
    log4j.appender.file.File=$ORACLE_HOME/bigdatalogs/bigdata-log4j.log

See Also:

Apache Logging Services documentation at

`http://logging.apache.org/log4j/1.2/manual.html`

### 3.8.3 About the Cluster Directory

The cluster directory contains configuration information for a Hadoop cluster. Each cluster that Oracle Database will access using Oracle Big Data SQL has a cluster directory. This directory is located on the Oracle Database system under the common directory. For example, a cluster named bda1_cl_1 would have a directory by the same name (`bda1_cl_1`) in the common directory.

The cluster directory contains the client configuration files for accessing the cluster, such as the following:

- `core-site.xml`

- `hdfs-site.xml`

- `hive-site.xml`

- `mapred-site.xml` (optional)

- `log4j` property files (such as `hive-log4j.properties`)

A database directory object points to the cluster directory. Users who want to access the data in a cluster must have read access to the directory object.

### 3.8.4 About Permissions

- On the Oracle database server, the `oracle` user (or whatever user owns the Oracle Database installation directory) requires READ/WRITE access to the database directory that points to the log directory.

- There must also be a corresponding `oracle` user defined in the Hadoop cluster. The `oracle` user requires READ access to HDFS on all DataNodes in the cluster.

1

0 for false, and 1 for true

2

FALSE maps to the string `FALSE`, and TRUE maps to the string `TRUE`.

3

FALSE maps to 0, and TRUE maps to 1.