hawq load

Acts as an interface to the external table parallel loading feature. Executes a load specification defined in a YAML-formatted control file to invoke the HAWQ parallel file server (gpfdist).

Synopsis

  1. hawq load -f <control_file> [-l <log_file>]   
  2.   [--gpfdist_timeout <seconds>] 
  3.   [[-v | -V] 
  4.   [-q]]
  5.   [-D]
  6.   [<connection_options>]
  8. hawq load -? 
  10. hawq load --version

where:

  1. <connection_options> =
  2.   [-h <host>] 
  3.   [-p <port>] 
  4.   [-U <username>] 
  5.   [-d <database>]
  6.   [-W]

Prerequisites

The client machine where hawq load is executed must have the following:

  • Python 2.6.2 or later, pygresql (the Python interface to PostgreSQL), and pyyaml. Note that Python and the required Python libraries are included with the HAWQ server installation, so if you have HAWQ installed on the machine where hawq load is running, you do not need a separate Python installation. Note: HAWQ Loaders for Windows supports only Python 2.5 (available from www.python.org).

  • The gpfdist parallel file distribution program installed and in your $PATH. This program is located in $GPHOME/bin of your HAWQ server installation.

  • Network access to and from all hosts in your HAWQ array (master and segments).

  • Network access to and from the hosts where the data to be loaded resides (ETL servers).

Description

hawq load is a data loading utility that acts as an interface to HAWQ’s external table parallel loading feature. Using a load specification defined in a YAML formatted control file, hawq load executes a load by invoking the HAWQ parallel file server (gpfdist), creating an external table definition based on the source data defined, and executing an INSERT operation to load the source data into the target table in the database.

The operation, including any SQL commands specified in the SQL collection of the YAML control file (see Control File Format), are performed as a single transaction to prevent inconsistent data when performing multiple, simultaneous load operations on a target table.

Arguments

-f <control_file>

A YAML file that contains the load specification details. See Control File Format.

Options

--gpfdist_timeout <seconds>

Sets the timeout for the gpfdist parallel file distribution program to send a response. Enter a value from 0 to 30 seconds (entering “0” to disables timeouts). Note that you might need to increase this value when operating on high-traffic networks.

-l <log_file>

Specifies where to write the log file. Defaults to ~/hawqAdminLogs/hawq_load_YYYYMMDD. For more information about the log file, see Log File Format.

-q (no screen output)

Run in quiet mode. Command output is not displayed on the screen, but is still written to the log file.

-D (debug mode)

Check for error conditions, but do not execute the load.

-v (verbose mode)

Show verbose output of the load steps as they are executed.

-V (very verbose mode)

Shows very verbose output.

-? (show help)

Show help, then exit.

--version

Show the version of this utility, then exit.

Connection Options

-d <database>

The database to load into. If not specified, reads from the load control file, the environment variable $PGDATABASE or defaults to the current system user name.

-h <hostname>

Specifies the host name of the machine on which the HAWQ master database server is running. If not specified, reads from the load control file, the environment variable $PGHOST or defaults to localhost.

-p <port>

Specifies the TCP port on which the HAWQ master database server is listening for connections. If not specified, reads from the load control file, the environment variable $PGPORT or defaults to 5432.

-U <username>

The database role name to connect as. If not specified, reads from the load control file, the environment variable $PGUSER or defaults to the current system user name.

-W (force password prompt)

Force a password prompt. If not specified, reads the password from the environment variable $PGPASSWORD or from a password file specified by $PGPASSFILE or in ~/.pgpass. If these are not set, then hawq load will prompt for a password even if -W is not supplied.

Control File Format

The hawq load control file uses the YAML 1.1 document format and then implements its own schema for defining the various steps of a HAWQ load operation. The control file must be a valid YAML document.

The hawq load program processes the control file document in order and uses indentation (spaces) to determine the document hierarchy and the relationships of the sections to one another. The use of white space is significant. White space should not be used simply for formatting purposes, and tabs should not be used at all.

The basic structure of a load control file is:

  1. ---
  2. VERSION: 1.0.0.1
  3. DATABASE: db_name
  4. USER: db_username
  5. HOST: master_hostname
  6. PORT: master_port
  7. GPLOAD:
  8.    INPUT:
  9.     - SOURCE:
  10.          LOCAL_HOSTNAME:
  11.            - hostname_or_ip
  12.          PORT: http_port
  13.        | PORT_RANGE: [start_port_range, end_port_range]
  14.          FILE: 
  15.            - /path/to/input_file
  16.          SSL: true | false
  17.          CERTIFICATES_PATH: /path/to/certificates
  18.     - COLUMNS:
  19.            - field_name: data_type
  20.     - TRANSFORM: 'transformation'
  21.     - TRANSFORM_CONFIG: 'configuration-file-path' 
  22.     - MAX_LINE_LENGTH: integer 
  23.     - FORMAT: text | csv
  24.     - DELIMITER: 'delimiter_character'
  25.     - ESCAPE: 'escape_character' | 'OFF'
  26.     - NULL_AS: 'null_string'
  27.     - FORCE_NOT_NULL: true | false
  28.     - QUOTE: 'csv_quote_character'
  29.     - HEADER: true | false
  30.     - ENCODING: database_encoding
  31.     - ERROR_LIMIT: integer
  32.     - ERROR_TABLE: schema.table_name
  33.    OUTPUT:
  34.     - TABLE: schema.table_name
  35.     - MODE: insert | update | merge
  36.     - MATCH_COLUMNS:
  37.            - target_column_name
  38.     - UPDATE_COLUMNS:
  39.            - target_column_name
  40.     - UPDATE_CONDITION: 'boolean_condition'
  41.     - MAPPING:
  42.               target_column_name: source_column_name | 'expression'
  43.    PRELOAD:
  44.     - TRUNCATE: true | false
  45.     - REUSE_TABLES: true | false
  46.    SQL:
  47.     - BEFORE: "sql_command"
  48.     - AFTER: "sql_command"

Control File Schema Elements

The control file contains the schema elements for:

  • Version
  • Database
  • User
  • Host
  • Port
  • GPLOAD file

VERSION

Optional. The version of the hawq load control file schema, for example: 1.0.0.1.

DATABASE

Optional. Specifies which database in HAWQ to connect to. If not specified, defaults to $PGDATABASE if set or the current system user name. You can also specify the database on the command line using the -d option.

USER

Optional. Specifies which database role to use to connect. If not specified, defaults to the current user or $PGUSER if set. You can also specify the database role on the command line using the -U option.

If the user running hawq load is not a HAWQ superuser, then the server configuration parameter gp_external_grant_privileges must be set to on for the load to be processed.

HOST

Optional. Specifies HAWQ master host name. If not specified, defaults to localhost or $PGHOST if set. You can also specify the master host name on the command line using the -h option.

PORT

Optional. Specifies HAWQ master port. If not specified, defaults to 5432 or $PGPORT if set. You can also specify the master port on the command line using the -p option.

GPLOAD

Required. Begins the load specification section. A GPLOAD specification must have an INPUT and an OUTPUT section defined.

INPUT

Required element. Defines the location and the format of the input data to be loaded. hawq load will start one or more instances of the gpfdist file distribution program on the current host and create the required external table definition(s) in HAWQ that point to the source data. Note that the host from which you run hawq load must be accessible over the network by all HAWQ hosts (master and segments).

SOURCE

Required. The SOURCE block of an INPUT specification defines the location of a source file. An INPUT section can have more than one SOURCE block defined. Each SOURCE block defined corresponds to one instance of the gpfdist file distribution program that will be started on the local machine. Each SOURCE block defined must have a FILE specification.

LOCAL_HOSTNAME

Optional. Specifies the host name or IP address of the local machine on which hawq load is running. If this machine is configured with multiple network interface cards (NICs), you can specify the host name or IP of each individual NIC to allow network traffic to use all NICs simultaneously. The default is to use the local machine’s primary host name or IP only.

PORT

Optional. Specifies the specific port number that the gpfdist file distribution program should use. You can also supply a PORT_RANGE to select an available port from the specified range. If both PORT and PORT_RANGE are defined, then PORT takes precedence. If neither PORT or PORT_RANGE are defined, the default is to select an available port between 8000 and 9000.

If multiple host names are declared in LOCAL_HOSTNAME, this port number is used for all hosts. This configuration is desired if you want to use all NICs to load the same file or set of files in a given directory location.

PORT_RANGE

Optional. Can be used instead of PORT to supply a range of port numbers from which hawq load can choose an available port for this instance of the gpfdist file distribution program.

FILE

Required. Specifies the location of a file, named pipe, or directory location on the local file system that contains data to be loaded. You can declare more than one file so long as the data is of the same format in all files specified.

If the files are compressed using gzip or bzip2 (have a .gz or .bz2 file extension), the files will be uncompressed automatically (provided that gunzip or bunzip2 is in your path).

When specifying which source files to load, you can use the wildcard character (*) or other C-style pattern matching to denote multiple files. The files specified are assumed to be relative to the current directory from which hawq load is executed (or you can declare an absolute path).

SSL

Optional. Specifies usage of SSL encryption.

CERTIFICATES_PATH

Required when SSL is true; cannot be specified when SSL is false or unspecified. The location specified in CERTIFICATES_PATH must contain the following files:

  • The server certificate file, server.crt
  • The server private key file, server.key
  • The trusted certificate authorities, root.crt

The root directory (/) cannot be specified as CERTIFICATES_PATH.

COLUMNS

Optional. Specifies the schema of the source data file(s) in the format of field_name:data_type. The DELIMITER character in the source file is what separates two data value fields (columns). A row is determined by a line feed character (0x0a).

If the input COLUMNS are not specified, then the schema of the output TABLE is implied, meaning that the source data must have the same column order, number of columns, and data format as the target table.

The default source-to-target mapping is based on a match of column names as defined in this section and the column names in the target TABLE. This default mapping can be overridden using the MAPPING section.

TRANSFORM

Optional. Specifies the name of the input XML transformation passed to hawq load. For more information about XML transformations, see “Loading and Unloading Data.”.

TRANSFORM_CONFIG

Optional. Specifies the location of the XML transformation configuration file that is specified in the TRANSFORM parameter, above.

MAX_LINE_LENGTH

Optional. An integer that specifies the maximum length of a line in the XML transformation data passed to hawq load.

FORMAT

Optional. Specifies the format of the source data file(s) - either plain text (TEXT) or comma separated values (CSV) format. Defaults to TEXT if not specified. For more information about the format of the source data, see “Loading and Unloading Data” .

DELIMITER

Optional. Specifies a single ASCII character that separates columns within each row (line) of data. The default is a tab character in TEXT mode, a comma in CSV mode.You can also specify a non-printable ASCII character via an escape sequence\ using the decimal representation of the ASCII character. For example, \014 represents the shift out character..

ESCAPE

Specifies the single character that is used for C escape sequences (such as \n, \t, \100, and so on) and for escaping data characters that might otherwise be taken as row or column delimiters. Make sure to choose an escape character that is not used anywhere in your actual column data. The default escape character is a \ (backslash) for text-formatted files and a " (double quote) for csv-formatted files, however it is possible to specify another character to represent an escape. It is also possible to disable escaping in text-formatted files by specifying the value 'OFF' as the escape value. This is very useful for data such as text-formatted web log data that has many embedded backslashes that are not intended to be escapes.

NULL_AS

Optional. Specifies the string that represents a null value. The default is \N (backslash-N) in TEXT mode, and an empty value with no quotations in CSV mode. You might prefer an empty string even in TEXT mode for cases where you do not want to distinguish nulls from empty strings. Any source data item that matches this string will be considered a null value.

FORCE_NOT_NULL

Optional. In CSV mode, processes each specified column as though it were quoted and hence not a NULL value. For the default null string in CSV mode (nothing between two delimiters), this causes missing values to be evaluated as zero-length strings.

QUOTE

Required when FORMAT is CSV. Specifies the quotation character for CSV mode. The default is double-quote (").

HEADER

Optional. Specifies that the first line in the data file(s) is a header row (contains the names of the columns) and should not be included as data to be loaded. If using multiple data source files, all files must have a header row. The default is to assume that the input files do not have a header row.

ENCODING

Optional. Character set encoding of the source data. Specify a string constant (such as 'SQL_ASCII'), an integer encoding number, or 'DEFAULT' to use the default client encoding. If not specified, the default client encoding is used.

ERROR_LIMIT

Optional. Sets the error limit count for HAWQ segment instances during input processing. Error rows will be written to the table specified in ERROR_TABLE. The value of ERROR_LIMIT must be 2 or greater.

ERROR_TABLE

Optional when ERROR_LIMIT is declared. Specifies an error table where rows with formatting errors will be logged when running in single row error isolation mode. You can then examine this error table to see error rows that were not loaded (if any). If the ERROR_TABLE specified already exists, it will be used. If it does not exist, it will be automatically generated.

For more information about handling load errors, see “Loading and Unloading Data”.

OUTPUT

Required element. Defines the target table and final data column values that are to be loaded into the database.

TABLE

Required. The name of the target table to load into.

MODE

Optional. Defaults to INSERT if not specified. There are three available load modes:

INSERT

Loads data into the target table using the following method:

  1. INSERT INTO target_table SELECT * FROM input_data;

UPDATE

Updates the UPDATE_COLUMNS of the target table where the rows have MATCH_COLUMNS attribute values equal to those of the input data, and the optional UPDATE_CONDITION is true.

MERGE

Inserts new rows and updates the UPDATE_COLUMNS of existing rows where MATCH_COLUMNS attribute values are equal to those of the input data, and the optional UPDATE_CONDITION is true. New rows are identified when the MATCH_COLUMNS value in the source data does not have a corresponding value in the existing data of the target table. In those cases, the entire row from the source file is inserted, not only the MATCH and UPDATE columns. If there are multiple new MATCH_COLUMNS values that are the same, only one new row for that value will be inserted. Use UPDATE_CONDITION to filter out the rows to discard.

MATCH_COLUMNS

Required if MODE is UPDATE or MERGE. Specifies the column(s) to use as the join condition for the update. The attribute value in the specified target column(s) must be equal to that of the corresponding source data column(s) in order for the row to be updated in the target table.

UPDATE_COLUMNS

Required if MODE is UPDATE or MERGE. Specifies the column(s) to update for the rows that meet the MATCH_COLUMNS criteria and the optional UPDATE_CONDITION.

UPDATE_CONDITION

Optional. Specifies a Boolean condition (similar to what you would declare in a WHERE clause) that must be met for a row in the target table to be updated (or inserted in the case of a MERGE).

MAPPING

Optional. If a mapping is specified, it overrides the default source-to-target column mapping. The default source-to-target mapping is based on a match of column names as defined in the source COLUMNS section and the column names of the target TABLE. A mapping is specified as either:

target_column_name: source_column_name

or

target_column_name: 'expression'

Where <expression> is any expression that you would specify in the SELECT list of a query, such as a constant value, a column reference, an operator invocation, a function call, and so on.

PRELOAD

Optional. Specifies operations to run prior to the load operation. Currently, the only preload operation is TRUNCATE.

TRUNCATE

Optional. If set to true, hawq load will remove all rows in the target table prior to loading it.

REUSE_TABLES

Optional. If set to true, hawq load will not drop the external table objects and staging table objects it creates. These objects will be reused for future load operations that use the same load specifications. Reusing objects improves performance of trickle loads (ongoing small loads to the same target table).

SQL

Optional. Defines SQL commands to run before and/or after the load operation. Commands that contain spaces or special characters must be enclosed in quotes. You can specify multiple BEFORE and/or AFTER commands. List commands in the desired order of execution.

BEFORE

Optional. A SQL command to run before the load operation starts. Enclose commands in quotes.

AFTER

Optional. A SQL command to run after the load operation completes. Enclose commands in quotes.

Notes

If your database object names were created using a double-quoted identifier (delimited identifier), you must specify the delimited name within single quotes in the hawq load control file. For example, if you create a table as follows:

  1. CREATE TABLE "MyTable" ("MyColumn" text);

Your YAML-formatted hawq load control file would refer to the above table and column names as follows:

  1. - COLUMNS:
  2.    - '"MyColumn"': text
  3. OUTPUT:
  4.    - TABLE: public.'"MyTable"'

Log File Format

Log files output by hawq load have the following format:

  1. timestamp|level|message

Where <timestamp> takes the form: YYYY-MM-DD HH:MM:SS, <level> is one of DEBUG, LOG, INFO, ERROR, and <message> is a normal text message.

Some INFO messages that may be of interest in the log files are (where # corresponds to the actual number of seconds, units of data, or failed rows):

  1. INFO|running time: #.## seconds
  2. INFO|transferred #.# kB of #.# kB.
  3. INFO|hawq load succeeded
  4. INFO|hawq load succeeded with warnings
  5. INFO|hawq load failed
  6. INFO|1 bad row
  7. INFO|# bad rows

Examples

Run a load job as defined in my_load.yml:

  1. $ hawq load -f my_load.yml

Example load control file:

  1. ---
  2. VERSION: 1.0.0.1
  3. DATABASE: ops
  4. USER: gpadmin
  5. HOST: mdw-1
  6. PORT: 5432
  7. GPLOAD:
  8.    INPUT:
  9.     - SOURCE:
  10.          LOCAL_HOSTNAME:
  11.            - etl1-1
  12.            - etl1-2
  13.            - etl1-3
  14.            - etl1-4
  15.          PORT: 8081
  16.          FILE: 
  17.            - /var/load/data/*
  18.     - COLUMNS:
  19.            - name: text
  20.            - amount: float4
  21.            - category: text
  22.            - desc: text
  23.            - date: date
  24.     - FORMAT: text
  25.     - DELIMITER: '|'
  26.     - ERROR_LIMIT: 25
  27.     - ERROR_TABLE: payables.err_expenses
  28.    OUTPUT:
  29.     - TABLE: payables.expenses
  30.     - MODE: INSERT
  31.    SQL:
  32.    - BEFORE: "INSERT INTO audit VALUES('start', current_timestamp)"
  33.    - AFTER: "INSERT INTO audit VALUES('end', 
  34. current_timestamp)"

See Also

gpfdist, CREATE EXTERNAL TABLE