FSTableDescriptors (Apache HBase 1.4.11 API)

java.lang.Object
- org.apache.hadoop.hbase.util.FSTableDescriptors

All Implemented Interfaces:

TableDescriptors
```
@InterfaceAudience.Private
public class FSTableDescriptors
extends Object
implements TableDescriptors
```
Implementation of TableDescriptors that reads descriptors from the passed filesystem. It expects descriptors to be in a file in the TABLEINFO_DIR subdir of the table's directory in FS. Can be read-only -- i.e. does not modify the filesystem or can be read and write.
Also has utility for keeping up the table descriptors tableinfo file. The table schema file is kept in the TABLEINFO_DIR subdir of the table directory in the filesystem. It has a TABLEINFO_FILE_PREFIX and then a suffix that is the edit sequenceid: e.g. .tableinfo.0000000003. This sequenceid is always increasing. It starts at zero. The table schema file with the highest sequenceid has the most recent schema edit. Usually there is one file only, the most recent but there may be short periods where there are more than one file. Old files are eventually cleaned. Presumption is that there will not be lots of concurrent clients making table schema edits. If so, the below needs a bit of a reworking and perhaps some supporting api in hdfs.

Constructor Summary

Constructors
Constructor and Description
`FSTableDescriptors(org.apache.hadoop.conf.Configuration conf)` Construct a FSTableDescriptors instance using the hbase root dir of the given conf and the filesystem where that root dir lives.
`FSTableDescriptors(org.apache.hadoop.conf.Configuration conf, org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path rootdir)`
`FSTableDescriptors(org.apache.hadoop.conf.Configuration conf, org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path rootdir, boolean fsreadonly, boolean usecache)`

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`add(HTableDescriptor htd)` Adds (or updates) the table descriptor to the FileSystem and updates the local cache with it.
`boolean`	`createTableDescriptor(HTableDescriptor htd)` Create new HTableDescriptor in HDFS.
`boolean`	`createTableDescriptor(HTableDescriptor htd, boolean forceCreation)` Create new HTableDescriptor in HDFS.
`boolean`	`createTableDescriptorForTableDirectory(org.apache.hadoop.fs.Path tableDir, HTableDescriptor htd, boolean forceCreation)` Create a new HTableDescriptor in HDFS in the specified table directory.
`void`	`deleteTableDescriptorIfExists(TableName tableName)` Deletes all the table descriptor files from the file system.
`HTableDescriptor`	`get(TableName tablename)` Get the current table descriptor for the given table, or null if none exists.
`Map<String,HTableDescriptor>`	`getAll()` Returns a map from table name to table descriptor for all tables.
`Map<String,HTableDescriptor>`	`getByNamespace(String name)` Get Map of all NamespaceDescriptors for a given namespace.
`static HTableDescriptor`	`getTableDescriptorFromFs(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path tableDir)` Returns the latest table descriptor for the table located at the given directory directly from the file system if it exists.
`static HTableDescriptor`	`getTableDescriptorFromFs(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path tableDir, boolean rewritePb)` Returns the latest table descriptor for the table located at the given directory directly from the file system if it exists.
`static HTableDescriptor`	`getTableDescriptorFromFs(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path hbaseRootDir, TableName tableName)` Returns the latest table descriptor for the given table directly from the file system if it exists, bypassing the local cache.
`static HTableDescriptor`	`getTableDescriptorFromFs(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path hbaseRootDir, TableName tableName, boolean rewritePb)` Returns the latest table descriptor for the table located at the given directory directly from the file system if it exists.
`static org.apache.hadoop.fs.FileStatus`	`getTableInfoPath(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path tableDir)` Find the most current table info file for the table located in the given table directory.
`boolean`	`isTableInfoExists(TableName tableName)` Checks if a current table info file exists for the given table
`boolean`	`isUsecache()`
`HTableDescriptor`	`remove(TableName tablename)` Removes the table descriptor from the local cache and returns it.
`void`	`setCacheOff()` Disables the tabledescriptor cache
`void`	`setCacheOn()` Enables the tabledescriptor cache

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - FSTableDescriptors
```
public FSTableDescriptors(org.apache.hadoop.conf.Configuration conf)
                   throws IOException
```
    Construct a FSTableDescriptors instance using the hbase root dir of the given conf and the filesystem where that root dir lives. This instance can do write operations (is not read only).
    
    Throws:
    
    IOException
  - FSTableDescriptors
```
public FSTableDescriptors(org.apache.hadoop.conf.Configuration conf,
                  org.apache.hadoop.fs.FileSystem fs,
                  org.apache.hadoop.fs.Path rootdir)
                   throws IOException
```
    Throws:
    
    IOException
  - FSTableDescriptors
```
public FSTableDescriptors(org.apache.hadoop.conf.Configuration conf,
                  org.apache.hadoop.fs.FileSystem fs,
                  org.apache.hadoop.fs.Path rootdir,
                  boolean fsreadonly,
                  boolean usecache)
                   throws IOException
```
    Parameters:
    fsreadonly - True if we are read-only when it comes to filesystem operations; i.e. on remove, we do not do delete in fs.
    
    Throws:
    
    IOException
- Method Detail
  - setCacheOn
```
public void setCacheOn()
                throws IOException
```
    Description copied from interface: TableDescriptors
    
    Enables the tabledescriptor cache
    
    Specified by:
    
    setCacheOn in interface TableDescriptors
    
    Throws:
    
    IOException
  - setCacheOff
```
public void setCacheOff()
                 throws IOException
```
    Description copied from interface: TableDescriptors
    
    Disables the tabledescriptor cache
    
    Specified by:
    
    setCacheOff in interface TableDescriptors
    
    Throws:
    
    IOException
  - isUsecache
```
public boolean isUsecache()
```
  - get
```
public HTableDescriptor get(TableName tablename)
                     throws IOException
```
    Get the current table descriptor for the given table, or null if none exists. Uses a local cache of the descriptor but still checks the filesystem on each call to see if a newer file has been created since the cached one was read.
    
    Specified by:
    
    get in interface TableDescriptors
    
    Returns:
    HTableDescriptor for tablename
    
    Throws:
    
    IOException
  - getAll
```
public Map<String,HTableDescriptor> getAll()
                                    throws IOException
```
    Returns a map from table name to table descriptor for all tables.
    
    Specified by:
    
    getAll in interface TableDescriptors
    
    Returns:
    Map of all descriptors.
    
    Throws:
    
    IOException
  - getByNamespace
```
public Map<String,HTableDescriptor> getByNamespace(String name)
                                            throws IOException
```
    Description copied from interface: TableDescriptors
    
    Get Map of all NamespaceDescriptors for a given namespace.
    
    Specified by:
    
    getByNamespace in interface TableDescriptors
    
    Returns:
    Map of all descriptors.
    
    Throws:
    
    IOException
  - add
```
public void add(HTableDescriptor htd)
         throws IOException
```
    Adds (or updates) the table descriptor to the FileSystem and updates the local cache with it.
    
    Specified by:
    
    add in interface TableDescriptors
    
    Parameters:
    htd - Descriptor to set into TableDescriptors
    
    Throws:
    
    IOException
  - remove
```
public HTableDescriptor remove(TableName tablename)
                        throws IOException
```
    Removes the table descriptor from the local cache and returns it. If not in read only mode, it also deletes the entire table directory(!) from the FileSystem.
    
    Specified by:
    
    remove in interface TableDescriptors
    
    Returns:
    Instance of table descriptor or null if none found.
    
    Throws:
    
    IOException
  - isTableInfoExists
```
public boolean isTableInfoExists(TableName tableName)
                          throws IOException
```
    Checks if a current table info file exists for the given table
    
    Parameters:
    tableName - name of table
    
    Returns:
    true if exists
    
    Throws:
    
    IOException
  - getTableInfoPath
```
public static org.apache.hadoop.fs.FileStatus getTableInfoPath(org.apache.hadoop.fs.FileSystem fs,
                                               org.apache.hadoop.fs.Path tableDir)
                                                        throws IOException
```
    Find the most current table info file for the table located in the given table directory. Looks within the TABLEINFO_DIR subdirectory of the given directory for any table info files and takes the 'current' one - meaning the one with the highest sequence number if present or no sequence number at all if none exist (for backward compatibility from before there were sequence numbers).
    
    Returns:
    The file status of the current table info file or null if it does not exist
    
    Throws:
    
    IOException
  - getTableDescriptorFromFs
```
public static HTableDescriptor getTableDescriptorFromFs(org.apache.hadoop.fs.FileSystem fs,
                                        org.apache.hadoop.fs.Path hbaseRootDir,
                                        TableName tableName)
                                                 throws IOException
```
    Returns the latest table descriptor for the given table directly from the file system if it exists, bypassing the local cache. Returns null if it's not found.
    
    Throws:
    
    IOException
  - getTableDescriptorFromFs
```
public static HTableDescriptor getTableDescriptorFromFs(org.apache.hadoop.fs.FileSystem fs,
                                        org.apache.hadoop.fs.Path hbaseRootDir,
                                        TableName tableName,
                                        boolean rewritePb)
                                                 throws IOException
```
    Returns the latest table descriptor for the table located at the given directory directly from the file system if it exists.
    
    Throws:
    
    TableInfoMissingException - if there is no descriptor
    
    IOException
  - getTableDescriptorFromFs
```
public static HTableDescriptor getTableDescriptorFromFs(org.apache.hadoop.fs.FileSystem fs,
                                        org.apache.hadoop.fs.Path tableDir)
                                                 throws IOException
```
    Returns the latest table descriptor for the table located at the given directory directly from the file system if it exists.
    
    Throws:
    
    TableInfoMissingException - if there is no descriptor
    
    IOException
  - getTableDescriptorFromFs
```
public static HTableDescriptor getTableDescriptorFromFs(org.apache.hadoop.fs.FileSystem fs,
                                        org.apache.hadoop.fs.Path tableDir,
                                        boolean rewritePb)
                                                 throws IOException
```
    Returns the latest table descriptor for the table located at the given directory directly from the file system if it exists.
    
    Throws:
    
    TableInfoMissingException - if there is no descriptor
    
    IOException
  - deleteTableDescriptorIfExists
```
public void deleteTableDescriptorIfExists(TableName tableName)
                                   throws IOException
```
    Deletes all the table descriptor files from the file system. Used in unit tests only.
    
    Throws:
    
    org.apache.commons.lang.NotImplementedException - if in read only mode
    
    IOException
  - createTableDescriptor
```
public boolean createTableDescriptor(HTableDescriptor htd)
                              throws IOException
```
    Create new HTableDescriptor in HDFS. Happens when we are creating table. Used by tests.
    
    Returns:
    True if we successfully created file.
    
    Throws:
    
    IOException
  - createTableDescriptor
```
public boolean createTableDescriptor(HTableDescriptor htd,
                            boolean forceCreation)
                              throws IOException
```
    Create new HTableDescriptor in HDFS. Happens when we are creating table. If forceCreation is true then even if previous table descriptor is present it will be overwritten
    
    Returns:
    True if we successfully created file.
    
    Throws:
    
    IOException
  - createTableDescriptorForTableDirectory
```
public boolean createTableDescriptorForTableDirectory(org.apache.hadoop.fs.Path tableDir,
                                             HTableDescriptor htd,
                                             boolean forceCreation)
                                               throws IOException
```
    Create a new HTableDescriptor in HDFS in the specified table directory. Happens when we create a new table or snapshot a table.
    
    Parameters:
    tableDir - table directory under which we should write the file
    htd - description of the table to write
    forceCreation - if true,then even if previous table descriptor is present it will be overwritten
    
    Returns:
    true if the we successfully created the file, false if the file already exists and we weren't forcing the descriptor creation.
    
    Throws:
    
    IOException - if a filesystem error occurs

Class FSTableDescriptors

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

FSTableDescriptors

FSTableDescriptors

FSTableDescriptors

Method Detail

setCacheOn

setCacheOff

isUsecache

get

getAll

getByNamespace

add

remove

isTableInfoExists

getTableInfoPath

getTableDescriptorFromFs

getTableDescriptorFromFs

getTableDescriptorFromFs

getTableDescriptorFromFs

deleteTableDescriptorIfExists

createTableDescriptor

createTableDescriptor

createTableDescriptorForTableDirectory