Altering Column Families

There are several methods that you can use to edit column families in MapR-DB tables. These methods also let you change permissions on column families.

Modifying a Column Family Using the MapR Control System

  1. Go to the table information page.
  2. Click Column Families tab.
    The page displays:
    • Default column family permissions
    • All the column families for the table
  3. Click the name of the column family to modify.
    The Edit Column Family page displays.
  4. Make changes to the following properties (under PROPERTIES) as desired.
    Column Family Name The name of the column family.
    Compression The compression setting to use for the column family. Valid options are off, lzf, lz4, and zlib. The default setting is the same as the compression setting for the directory where the table is located. To find out whether a directory is compressed and the type of compression, see Turning Compression On or Off on Directories Using the CLI.
    In Memory Determines whether preference is given to values of this column family for storage with row keys. Because row keys are cached in memory in preference to row data, column-family data that is stored inline with the row keys is also cached in memory.

    For all column families in a table together, up to 200 bytes of row data will be stored inline with each row key. Storing data inline with a row key might speed retrieval of the data from a column family because disk access can often be avoided. For each column family, up to 32 bytes can be stored inline with each row key even if this is disabled (No), but preference will be given to column families where this is enabled (Yes). A column family can have more than 32 bytes stored inline if this is enabled.

    If the total number of bytes for all column families together exceeds 200 for a row, then preference for inclusion within the inline storage for that row is given to column families that have this enabled.

    Note: All of the data for a column family will be stored in-line with the row key, or none will be. If the contents in a column family for a particular row are larger than the maximum number of bytes that are allowed to be stored for that column family, no data will be stored in-line for that column family.
    By default, this is enabled.
    Column Family Name The name of the column family.
    Version
    • Minimum — The minimum number of versions of column values to keep. The default is zero.
    • Maximum — Maximum number of versions of column values to keep. The default is one.
    Compression The compression setting to use for the column family. Valid options are off, lzf, lz4, and zlib. The default setting is the same as the compression setting for the directory where the table is located. To find out whether a directory is compressed and the type of compression, see Turning Compression On or Off on Directories Using the CLI.
    Time-to-Live Specifies whether to purge data when the age of the data in this column family exceeds the value specified here. Data can remain forever or can be purged after specified amount of time (in seconds). Setting the value to 0 is equivalent to allowing data to remain indefinitely or forever.
    In Memory Determines whether preference is given to values of this column family for storage with row keys. Because row keys are cached in memory in preference to row data, column-family data that is stored inline with the row keys is also cached in memory.

    For all column families in a table together, up to 200 bytes of row data will be stored inline with each row key. Storing data inline with a row key might speed retrieval of the data from a column family because disk access can often be avoided. For each column family, up to 32 bytes can be stored inline with each row key even if this is disabled (No), but preference will be given to column families where this is enabled (Yes). A column family can have more than 32 bytes stored inline if this is enabled.

    If the total number of bytes for all column families together exceeds 200 for a row, then preference for inclusion within the inline storage for that row is given to column families that have this enabled.

    Note: All of the data for a column family will be stored in-line with the row key, or none will be. If the contents in a column family for a particular row are larger than the maximum number of bytes that are allowed to be stored for that column family, no data will be stored in-line for that column family.
    By default, this is enabled.
  5. Make changes to permissions as desired.
    1. Modify USER ACCESS CONTROLs for the column family as desired.
      Modify or set the following permissions for the column family:
      Read Data Can do column reads. Reads require permission both at the column-family level and at the field level. This permission is inherited by fields within the column family.
      Write Data Can do column writes. Writes require permission both at the column-family level and at the field level. This permission is inherited by fields within the column family.
      Traverse Data Can pass over fields in JSON documents. For example, suppose that a JSON table contains documents of this general structure:
      {
           "_id" : "ID",
           "a" :
                {
                     "b" : "value",
                     "c" : "value"
                }
      }
      Suppose further that the user sjohnson has read permission on a.b, but not on a. For sjohnson to read a.b, the user needs the traverse permission on a. The user can then pass over field a to a.b. This permission is inherited by fields within the column family.
      Set Compression Can set or change the compression setting for the column family.
      Modify or set the following permissions for the column family:
      Read Data Can do column reads. Reads require permission both at the column-family level and at the field level. This permission is inherited by fields within the column family.
      Write Data Can do column writes. Writes require permission both at the column-family level and at the field level. This permission is inherited by fields within the column family.
      Append Data Can do column appends. Column appends require permission both at the column-family level and at the column level.
      Set Version Can set or change the maximum and minimum number of versions of column values to keep.
      Set Compression Can set or change the compression setting for the column family.
    2. Modify or set:
      Modify permissions for the following on existing fields and/or create new fields and set permissions for the following on the new fields:
      Read Data Can read from the field. This permission extends to fields that are nested below as well unless explicitly denied on any of the nested fields.
      Write Data Can delete the field, insert a value into the field, or overwrite the field's value.
      Note: Deleting a field also deletes all fields that are nested within that field, even those fields on which the write permission is explicitly denied.
      JSON Traverse Can descend a hierarchy of fields to access the fields to read or write.
      Modify following permissions for existing columns and/or create new columns and set permissions for the following:
      Read Data Can do column reads. Reads require permission both at the column-family level and at the field level. This permission is inherited by fields within the column family.
      Write Data Can do column writes. Writes require permission both at the column-family level and at the field level. This permission is inherited by fields within the column family.
      Append Data Can do column appends. Column appends require permission both at the column-family level and at the column level.
    To grant or block access to users, groups, and/or roles, from the:
    • Basic settings, select the type — public, (OR) user, group, or role — from the drop-down menu, specify the name of the user, group, or role, and select one or more checkbox to grant permissions.
      Tip: Click to create a copy of the associated access control setting. Click to remove the associated access control expression.
      To add access control expressions for another user, group, or role, click Add Another and repeat this step.
    • Advanced settings, or specify public (p) or user (u), group (g), and/or role (r) who have and/or do not have the type of access using the following boolean expressions and subexpressions:
      • ! — Negation operator.
      • & — AND operation.
      • | — OR operation.
      Use (), parentheses, for subexpressions.
      Note: You cannot specify user, group, or role individually if access is granted to all users (public).

      Alternatively, click associated with the type of access to use the Access Control Expression window to define access for public or users, group, and/or role. See Defining ACEs for more information.

    Note: If you switch from Basic to Advanced, the basic settings, if any, will be carried over to the advanced settings. If you switch from Advanced to Basic, all the settings will be lost because the subexpressions and AND (&) and negation (!) operations that are supported by advanced settings are not supported in the basic settings.
  6. Click Save Changes for the changes to take effect.

Modifying a Column Family Using the CLI or REST API

The basic command to edit a column family is:
maprcli table cf edit -path <path> -cfname <name_of_column_family> options
For the full list of options for this command, see table cf edit.

The format of the value of the -path parameter depends on whether you are creating a table on a local cluster or a remote cluster:

  • For a path on the local cluster, start the path at the volume mount point. For example, for a table named test under a volume with a mount point at /volume1, specify the following path: /volume1/test
  • For a path on a remote cluster, you must also specify the cluster name in the path. For example, for a table named customer under volume1 in the sanfrancisco cluster, specify the following path:/mapr/sanfrancisco/volume1/customer

Modifying a Column Family in a Binary Table Using HBase shell

After starting the HBase shell, run the alter command. Type help to see a list of commands and their syntax.