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  2. Data Warehouse Service
  3. Developer Guide
  4. Data Import
  5. Using GDS to Import Data from a Remote Server
  6. Example

Example

Example: Parallel Import from Multiple Data Servers

The data servers reside on the same intranet as the cluster. Their IP addresses are 192.168.0.90 and 192.168.0.91. Source data files are in CSV format.

  1. Create the target table tpcds.reasons.
    CREATE TABLE tpcds.reasons
    (
      r_reason_sk integer not null,
      r_reason_id char(16) not null,
      r_reason_desc char(100)
    );
  2. Log in to each GDS data server as user root and create the /input_data directory for storing data files on the servers. The following takes the data server whose IP address is 192.168.0.90 as an example. Operations on the other server are the same.
    mkdir -p /input_data
  3. (Optional) Create a user and the user group it belongs to. The user is used to start GDS. If the user and user group already exist, skip this step.
    groupadd gdsgrp
    useradd -g gdsgrp gds_user
  4. Evenly distribute source data files to the /input_data directories on the data servers.
  5. Change the owners of source data files and the /input_data directory on each data server to gds_user. The data server with the IP address 192.168.0.90 is used as an example.
    chown -R gds_user:gdsgrp /input_data 
  6. Log in to each data server as user gds_user and start GDS.

    The GDS installation path is /opt/bin/gds. Source data files are stored in /input_data/. The IP addresses of the data servers are 192.168.0.90 and 192.168.0.91. The GDS listening port is 5000. GDS runs in daemon mode.

    Start GDS on the data server whose IP address is 192.168.0.90.
    /gds/gds -d /input_data -p 192.168.0.90:5000 -H 10.10.0.1/24 -D

    Start GDS on the data server whose IP address is 192.168.0.91.

    /gds/gds -d /input_data -p 192.168.0.91:5000 -H 10.10.0.1/24  -D
  7. Create the foreign table tpcds.foreign_tpcds_reasons for the source data.

    Set import mode parameters as follows:

    • Set the import mode to Normal.
    • When GDS is started, the source data file directory is /input_data and the GDS listening port is 5000. Therefore, set location to gsfs://192.168.0.90:5000/* | gsfs://192.168.0.91:5000/*.

    Information about the data format is set based on data format parameters specified during data export. The parameter settings are as follows:

    • format is set to CSV.
    • encoding is set to UTF-8.
    • delimiter is set to E'\x08'.
    • quote is set to 0x1b.
    • null is set to an empty string without quotation marks.
    • escape is set to a double quotation mark.
    • header is set to false, indicating that the first row is regarded as a data row when a file is imported.

    Set import error tolerance parameters as follows:

    • Set PER NODE REJECT LIMIT (number of allowed data format errors) to unlimited. In this case, all the data format errors detected during data import will be tolerated.
    • Set LOG INTO to err_tpcds_reasons. The data format errors detected during data import will be recorded in the err_tpcds_reasons table.

    Based on the above settings, the foreign table is created using the following statement:

    CREATE FOREIGN TABLE tpcds.foreign_tpcds_reasons
    (
      r_reason_sk integer not null,
      r_reason_id char(16) not null,
      r_reason_desc char(100)
    )
    SERVER gsmpp_server OPTIONS (location 'gsfs://192.168.0.90:5000/* | gsfs://192.168.0.91:5000/*', formate 'CSV',mode 'Normal', encoding 'utf8', delimter E'\x08', quote E'\x1b', null '', fill_missing_fields 'false') LOG INTO err_tpcds_reasons PER NODE REJECT LIMIT 'unlimited';
  8. Import data through the foreign table tpcds.foreign_tpcds_reasons to the target table tpcds.reasons.
    INSERT INTO tpcds.reasons SELECT * FROM tpcds.foreign_tpcds_reasons;
  9. Query data import errors in the err_tpcds_reasons table and rectify the errors (if any). For details, see Handling Import Errors.
    SELECT * FROM err_tpcds_reasons;
  10. After data import is complete, log in to each data server as user gds_user and stop GDS.
    The data server with the IP address 192.168.0.90 is used as an example. The GDS process ID is 128954.
    ps -ef|grep gds
    gds_user 128954      1  0 15:03 ?        00:00:00 gds -d /input_data -p 192.168.0.90:5000 -D
    gds_user 129003 118723  0 15:04 pts/0    00:00:00 grep gds
    kill -9 128954
    

Example: Data Import Using Multiple Threads

The data server resides on the same intranet as the cluster. The server IP address is 192.168.0.90. Source data files are in CSV format. Data will be imported to two tables using multiple threads in Normal mode.

  1. In the database, create the target tables tpcds.reasons1 and tpcds.reasons2.
    CREATE TABLE tpcds.reasons1
    (
      r_reason_sk integer not null,
      r_reason_id char(16) not null,
      r_reason_desc char(100)
    ) ;
    CREATE TABLE tpcds.reasons2
    (
      r_reason_sk integer not null,
      r_reason_id char(16) not null,
      r_reason_desc char(100)
    ) ;
  2. Log in to the GDS data server as user root, and then create the data file directory /input_data and its sub-directories /input_data/import1/ and /input_data/import2/.
    mkdir -p /input_data
  3. Store the source data files of the target table tpcds.reasons1 in /input_data/import1/ and the source data files of the target table tpcds.reasons2 in /input_data/import2/.
  4. (Optional) Create a user and the user group it belongs to. The user is used to start GDS. If the user and user group already exist, skip this step.
    groupadd gdsgrp
    useradd -g gdsgrp gds_user
  5. Change the owners of source data files and the /input_data directory on the data server to gds_user.
    chown -R gds_user:gdsgrp /input_data 
  6. Log in to the data server as user gds_user and start GDS.
    The GDS installation path is /gds. Source data files are stored in /input_data/. The IP address of the data server is 192.168.0.90. The GDS listening port is 5000. GDS runs in daemon mode. The degree of parallelism is 2. A recursive directory is specified.
    /gds/gds -d /input_data -p 192.168.0.90:5000 -H 10.10.0.1/24  -D -t 2 -r
  7. In the database, create the foreign tables tpcds.foreign_tpcds_reasons1 and tpcds.foreign_tpcds_reasons2 for the source data.

    The foreign table tpcds.foreign_tpcds_reasons1 is used as an example to describe how to set parameters in a foreign table.

    Set import mode parameters as follows:

    • Set the import mode to Normal.
    • When GDS is started, the configured source data file directory is /input_data and the GDS listening port is 5000. However, source data files are actually stored in /input_data/import1/. Therefore, set location to gsfs://192.168.0.90:5000/import1/*.

    Information about the data format is set based on data format parameters specified during data export. The parameter settings are as follows:

    • format is set to CSV.
    • encoding is set to UTF-8.
    • delimiter is set to E'\x08'.
    • quote is set to 0x1b.
    • null is set to an empty string without quotation marks.
    • escape is set to a double quotation mark.
    • header is set to false, indicating that the first row is regarded as a data row when a file is imported.

    Set import error tolerance parameters as follows:

    • Set PER NODE REJECT LIMIT (number of allowed data format errors) to unlimited. In this case, all the data format errors detected during data import will be tolerated.
    • Set LOG INTO to err_tpcds_reasons1. The data format errors detected during data import will be recorded in the err_tpcds_reasons1 table.
    • If the last column (fill_missing_fields) in a source data file is missing, the NULL column will be automatically added to the target file.

    Based on the above settings, the foreign table tpcds.foreign_tpcds_reasons1 is created using the following statement:

    CREATE FOREIGN TABLE tpcds.foreign_tpcds_reasons1
    (
      r_reason_sk integer not null,
      r_reason_id char(16) not null,
      r_reason_desc char(100)
    ) SERVER gsmpp_server OPTIONS (location 'gsfs://192.168.0.90:5000/import1/*', format 'CSV',mode 'Normal', encoding 'utf8', delimiter E'\x08', quote E'\x1b', null '',fill_missing_fields 'on')LOG INTO err_tpcds_reasons1 PER NODE REJECT LIMIT 'unlimited';

    Based on the above settings, the foreign table tpcds.foreign_tpcds_reasons2 is created using the following statement:

    CREATE FOREIGN TABLE tpcds.foreign_tpcds_reasons2
    (
      r_reason_sk integer not null,
      r_reason_id char(16) not null,
      r_reason_desc char(100)
    ) SERVER gsmpp_server OPTIONS (location 'gsfs://192.168.0.90:5000/import2/*', format 'CSV',mode 'Normal', encoding 'utf8', delimiter E'\x08', quote E'\x1b', null '',fill_missing_fields 'on')LOG INTO err_tpcds_reasons2 PER NODE REJECT LIMIT 'unlimited';
  8. Import data through the foreign table tpcds.foreign_tpcds_reasons1 to tpcds.reasons1 and through tpcds.foreign_tpcds_reasons2 to tpcds.reasons2.
    INSERT INTO tpcds.reasons1 SELECT * FROM tpcds.foreign_tpcds_reasons1;
    INSERT INTO tpcds.reasons2 SELECT * FROM tpcds.foreign_tpcds_reasons2;
  9. Query data import errors in the err_tpcds_reasons1 and err_tpcds_reasons2 tables and rectify the errors (if any). For details, see Handling Import Errors.
    SELECT * FROM err_tpcds_reasons1;
    SELECT * FROM err_tpcds_reasons2;
  10. After data import is complete, log in to the data server as user gds_user and stop GDS.
    The GDS process ID is 128954.
    ps -ef|grep gds
    gds_user 128954      1  0 15:03 ?        00:00:00 gds -d /input_data -p 192.168.0.90:5000 -D -t 2 -r
    gds_user 129003 118723  0 15:04 pts/0    00:00:00 grep gds
    kill -9 128954