COMMAND NAME: hawq extract

Extract table's metadata into a YAML file.

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SYNOPSIS
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hawq extract [-h hostname] [-p port] [-U username] [-d database] [-o output_file] [-W] <tablename>

hawq extract help 
hawq extract -? 

hawq extract --version

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DESCRIPTION
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Hawq extract is a utility to extract table's metadata into
a YAML formatted file. The file then can be consumed by
HAWQ's InputFormat to make HAWQ's data file on HDFS be
read directly in MapReduce program.

To use hawq extract, HAWQ must have been already started.

Currently hawq extract supports AO table only. Partition
table is supported, however multi-level partitions is
not supported.

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Arguments
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<tablename>

Name of the table to extract metadata. It can be 'namespace_name.table_name'
or just 'table_name' if the namespace name is 'public'.

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OPTIONS
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-o output_file

Specifies the name of a file that hawq extract will write the table's metadata to. If not specified, hawq extract will write to stdout.

-v (verbose mode)

Optional. Show verbose output of the extract steps as they are executed.

-? (help)

Displays the online help.

--version

Displays the version of this utility.

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CONNECTION OPTIONS
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-d database

  The database to connect to. If not specified, reads from the
  environment variable $PGDATABASE or defaults to 'template1'. 

-h hostname
  
  Specifies the host name of the machine on which the HAWQ master
  database server is running. If not specified, reads from 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
  environment variable $PGPORT or defaults to 5432.

-U username

  The database role name to connect as. If not specified, reads
  from 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. 

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METADATA FILE FORMAT
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The hawq extract will export table's metadata into a file using YAML 1.1
document format. The file contains various key information of the table,
such as table's schema, data file's locations and sizes, partition
constraints and so on.

The basic structure of the metadata file is:
---

Version: string (1.0.0)
DBVersion: string
FileFormat: string (AO/Parquet)
TableName: string (schemaname.tablename)
DFS_URL: string (hdfs://127.0.0.1:9000)
Encoding: UTF8
AO_Schema: 
- name: string
  type: string

AO_FileLocations:
  Blocksize: int
  Checksum: boolean
  CompressionType: string
  CompressionLevel: int
  PartitionBy: string ('PARTITION BY ...')
  Files:
  - path: string (/gpseg0/16385/35469/35470.1)
    size: long
  
  Partitions:
  - Blocksize: int
    Checksum: boolean
    CompressionType: string
    CompressionLevel: int
    Name: string
    Constraint: string (PARTITION Jan08 START (date '2008-01-01') INCLUSIVE)
    Files:
    - path: string
      size: long

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EXAMPLES
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Run hawq extract to extract 'rank' table's metadata into
a file 'rank_table.yaml'.

$ hawq extract -o rank_table.yaml rank

Output content in rank_table.yaml
---------------------------------
AO_FileLocations:
  Blocksize: 32768
  Checksum: false
  CompressionLevel: 0
  CompressionType: null
  Files:
  - path: /gpseg0/16385/35469/35692.1
    size: 0
  - path: /gpseg1/16385/35469/35692.1
    size: 0
  PartitionBy: PARTITION BY list (gender)
  Partitions:
  - Blocksize: 32768
    Checksum: false
    CompressionLevel: 0
    CompressionType: null
    Constraint: PARTITION girls VALUES('F') WITH (appendonly=true)
    Files:
    - path: /gpseg0/16385/35469/35697.1
      size: 0
    - path: /gpseg1/16385/35469/35697.1
      size: 0
    Name: girls
  - Blocksize: 32768
    Checksum: false
    CompressionLevel: 0
    CompressionType: null
    Constraint: PARTITION boys VALUES('M') WITH (appendonly=true)
    Files:
    - path: /gpseg0/16385/35469/35703.1
      size: 0
    - path: /gpseg1/16385/35469/35703.1
      size: 0
    Name: boys
  - Blocksize: 32768
    Checksum: false
    CompressionLevel: 0
    CompressionType: null
    Constraint: DEFAULT PARTITION other  WITH (appendonly=true)
    Files:
    - path: /gpseg0/16385/35469/35709.1
      size: 90071728
    - path: /gpseg1/16385/35469/35709.1
      size: 90071512
    Name: other
AO_Schema:
- name: id
  type: int4
- name: rank
  type: int4
- name: year
  type: int4
- name: gender
  type: bpchar
- name: count
  type: int4
DBVersion: PostgreSQL 8.2.15 (Greenplum Database 4.2.0 build 1) (HAWQ 1.0.0.3 build) on i386-apple-darwin11.4.2, compiled by GCC gcc (GCC) 4.4.2
DFS_URL: hdfs://127.0.0.1:9000
Encoding: UTF8
FileFormat: AO
TableName: public.rank
Version: 1.0.0

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SEE ALSO
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hawq load