in Cassandra-CLI Wie bekomme ich alle Spaltennamen in einer Tabelle und wie bekomme ich Hector in Java?

Question

Ich versuche, Spaltennamen zu bekommen, konnte aber nicht nur Spaltennamen bekommen.

In cli Ausgeführt ich Befehl describe table nodes, kehrt er das Ergebnis:

CREATE TABLE nodes (
    key text PRIMARY KEY, 
    id text, 
    scores text, 
    topic1 text, 
    topic2 text, 
    topic3 text, 
    topic4 text, 
    topics text 
) WITH COMPACT STORAGE AND 
    bloom_filter_fp_chance=0.010000 AND 
    caching='KEYS_ONLY' AND 
    comment='' AND 
    dclocal_read_repair_chance=0.000000 AND 
    gc_grace_seconds=864000 AND 
    read_repair_chance=0.100000 AND 
    replicate_on_write='true' AND 
    populate_io_cache_on_flush='false' AND 
    compaction={'class': 'SizeTieredCompactionStrategy'} AND 
    compression={'sstable_compression': 'SnappyCompressor'}; 

CREATE INDEX idx_nodes_id ON nodes (id); 

Wie in diesen question gegeben, ich in cli folgenden Befehl versucht, mit:

SELECT column_name FROM system.schema_columnfamilies WHERE keyspace_name = 'ianew' AND columnfamily_name = 'nodes'; 

aber es gab den Fehler:

Bad Request: Undefined name column_name in selection clause 
Perhaps you meant to use CQL 2? Try using the -2 option when starting cqlsh. 

Dann habe ich versucht mit:

SELECT * FROM system.schema_columnfamilies WHERE keyspace_name = 'ianew' AND columnfamily_name = 'nodes'; 

Es alle folgenden Dinge zurückgegeben: Wie

keyspace_name | columnfamily_name | bloom_filter_fp_chance | caching | column_aliases | comment | compaction_strategy_class          | compaction_strategy_options | comparator        | compression_parameters              | default_read_consistency | default_validator      | default_write_consistency | gc_grace_seconds | id | key_alias | key_aliases | key_validator       | local_read_repair_chance | max_compaction_threshold | min_compaction_threshold | populate_io_cache_on_flush | read_repair_chance | replicate_on_write | subcomparator | type  | value_alias 
---------------+-------------------+------------------------+-----------+----------------+---------+-----------------------------------------------------------------+-----------------------------+------------------------------------------+-----------------------------------------------------------------------------+--------------------------+------------------------------------------+---------------------------+------------------+------+-----------+-------------+------------------------------------------+--------------------------+--------------------------+--------------------------+----------------------------+--------------------+--------------------+---------------+----------+------------- 
     ianew |    nodes |     null | KEYS_ONLY |    [] |   | org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy |       {} | org.apache.cassandra.db.marshal.UTF8Type | {"sstable_compression":"org.apache.cassandra.io.compress.SnappyCompressor"} |      null | org.apache.cassandra.db.marshal.UTF8Type |      null |   864000 | null |  null |   [] | org.apache.cassandra.db.marshal.UTF8Type |      0 |      32 |      4 |      False |    0.1 |    True |   null | Standard |  null 

in diesem post gegeben, habe ich versucht, hector in java:

SliceQuery<String, String, String> query = HFactory.createSliceQuery(keyspace, StringSerializer.get(), StringSerializer.get(), StringSerializer.get()); 
query.setColumnFamily(columnFamilyName); 
query.setKey("key"); 
query.setRange(null, null, false, Integer.MAX_VALUE); 

ColumnSliceIterator<String, String, String> iterator = new ColumnSliceIterator<String, String, String>(query, null, "\uFFFF", false); 

while (iterator.hasNext()) { 
    HColumnImpl<String, String> column = (HColumnImpl<String, String>) iterator.next(); 
    System.out.println("Column name = " + column.getName() + "; Column value = " + column.getValue()); 
    colNames.add(column.getName()); 
} 

aber ohne Treffer.

Ich möchte eine Ausgabe wie etwas sein:

TABLE nodes: 
Columns: key text PRIMARY KEY, id text, scores text, topic1 text, topic2 text, topic3 text, topic4 text, topics text 

und ähnliches Ergebnis durch Hector.

Versionen Ich verwende:

[cqlsh 2.3.0 | Cassandra 1.2.4 | CQL spec 3.0.0 | Thrift protocol 19.35.0] 

Answer 1

In cassandra 1.1, die in der Tat funktionieren würde, aber die schema_columnfamilies Spalte Familie hat sich seitdem geändert.

Bad Request: Undefined name column_name in selection clause

In Cassandra 1.2.x Informationen über die Spalten wohnt in einem separaten Schlüsselraum genannt schema_columns mit folgendem Schema:

CREATE TABLE schema_columns (
    keyspace_name text, 
    columnfamily_name text, 
    column_name text, 
    component_index int, 
    index_name text, 
    index_options text, 
    index_type text, 
    validator text, 
    PRIMARY KEY (keyspace_name, columnfamily_name, column_name) 
); 

etwas in dieser Richtung versuchen:

SELECT * FROM system.schema_columns 
WHERE keyspace_name = 'ianew' AND columnfamily_name = 'nodes'; 

Documentation auf, was der Inhalt des Systems Schlüsselraum.