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Avro Data Stored in HBase ColumnsAs of Hive 0.9.0 the HBase integration requires at least HBase 0.92, earlier versions of Hive were working with HBase 0.89/0.90 |
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CREATE TABLE hbase_table_1(key int, value string)
STORED BY 'org.apache.hadoop.hive.hbase.HBaseStorageHandler'
WITH SERDEPROPERTIES ("hbase.columns.mapping" = ":key,cf1:val")
TBLPROPERTIES ("hbase.table.name" = "xyz", "hbase.mapred.output.outputtable" = "xyz");
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The hbase.columns.mapping
property is required and will be explained in the next section. The hbase.table.name
property is optional; it controls the name of the table as known by HBase, and allows the Hive table to have a different name. In this example, the table is known as hbase_table_1
within Hive, and as xyz
within HBase. If not specified, then the Hive and HBase and HBase table names will be identical. The hbase.mapred.output.outputtable
property is optional; it's needed if you plan to insert data to the table (the property is used by hbase.mapreduce.TableOutputFormat
)
After executing the command above, you should be able to see the new (empty) table in the HBase shell:
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CREATE EXTERNAL TABLE hbase_table_2(key int, value string)
STORED BY 'org.apache.hadoop.hive.hbase.HBaseStorageHandler'
WITH SERDEPROPERTIES ("hbase.columns.mapping" = "cf1:val")
TBLPROPERTIES("hbase.table.name" = "some_existing_table", "hbase.mapred.output.outputtable" = "some_existing_table");
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Again, hbase.columns.mapping
is required (and will be validated against the existing HBase table's column families), whereas hbase.table.name
is optional. The hbase.mapred.output.outputtable
is optional.
Column Mapping
There are two SERDEPROPERTIES
that control the mapping of HBase columns to Hive:
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- for each Hive column, the table creator must specify a corresponding entry in the comma-delimited
hbase.columns.mapping
string (so for a Hive table with n columns, the string should have n entries); whitespace should not be used in between entries since these will be interperted as part of the column name, which is almost certainly not what you want - a mapping entry must be either
:key
,:timestamp
or of the formcolumn-family-name:[column-name][#(binary|string)
(the type specification that delimited by # was added in Hive 0.9.0, earlier versions interpreted everything as strings)- If no type specification is given the value from
hbase.table.default.storage.type
will be used - Any prefixes of the valid values are valid too (i.e.
#b
instead of#binary
) - If you specify a column as
binary
the bytes in the corresponding HBase cells are expected to be of the form that HBase'sBytes
class yields.
- If no type specification is given the value from
- there must be exactly one
:key
mapping (this can be mapped either to a string or struct column–see Simple Composite Keys and Complex Composite Keys) - (note that before HIVE-1228 in Hive 0.6,
:key
was not supported, and the first Hive column implicitly mapped to the key; as of Hive 0.6, it is now strongly recommended that you always specify the key explictly; we will drop support for implicit key mapping in the future) - if no column-name is given, then the Hive column will map to all columns in the corresponding HBase column family, and the Hive MAP datatype must be used to allow access to these (possibly sparse) columns
- Since HBase 1.1 (HBASE-2828) there is currently no a way to access the HBase timestamp attribute , and queries always access data with the latest timestamp.Since HBase does not associate datatype information with columns, the serde converts everything to string representation before storing it in HBase; there is currently no way to plug in a custom serde per columnusing the special
:timestamp
mapping. It needs to be eitherbigint
ortimestamp
. - it is not necessary to reference every HBase column family, but those that are not mapped will be inaccessible via the Hive table; it's possible to map multiple Hive tables to the same HBase table
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-- Parse a row key with 3 fixed width fields each of width 10 -- Example taken from: https://svn.apache.org/repos/asf/hive/trunk/hbase-handler/src/test/queries/positive/hbase_custom_key2.q CREATE TABLE hbase_ck_4(key struct<col1:string,col2:string,col3:string>, value string) STORED BY 'org.apache.hadoop.hive.hbase.HBaseStorageHandler' WITH SERDEPROPERTIES ( "hbase.table.name" = "hbase_custom2", "hbase.mapred.columns.mappingoutput.outputtable" = "hbase_custom2", "hbase.columns.mapping" = ":key,cf:string", "hbase.composite.key.factory"="org.apache.hadoop.hive.hbase.SampleHBaseKeyFactory2"); |
"hbase.composite.key.factory" should be the fully qualified class name of a class implementing HBaseKeyFactory. See SampleHBaseKeyFactory2 for a fixed length example in the same package. This class must be on your classpath in order for the above example to work. TODO: place these in an accessible place; they're currently only in test code..factory" should be the fully qualified class name of a class implementing HBaseKeyFactory. See SampleHBaseKeyFactory2 for a fixed length example in the same package. This class must be on your classpath in order for the above example to work. TODO: place these in an accessible place; they're currently only in test code.
Avro Data Stored in HBase Columns
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As of Hive 0.14.0 with HIVE-6147 |
Hive 0.14.0 onward supports storing and querying Avro objects in HBase columns by making them visible as structs to Hive. This allows Hive to perform ad hoc analysis of HBase data which can be deeply structured. Prior to 0.14.0, the HBase Hive integration only supported querying primitive data types in columns.
An example HiveQL statement where test_col_fam
is the column family and test_col
is the column name:
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CREATE EXTERNAL TABLE test_hbase_avro
ROW FORMAT SERDE 'org.apache.hadoop.hive.hbase.HBaseSerDe'
STORED BY 'org.apache.hadoop.hive.hbase.HBaseStorageHandler'
WITH SERDEPROPERTIES (
"hbase.columns.mapping" = ":key,test_col_fam:test_col",
"test_col_fam.test_col.serialization.type" = "avro",
"test_col_fam.test_col.avro.schema.url" = "hdfs://testcluster/tmp/schema.avsc")
TBLPROPERTIES (
"hbase.table.name" = "hbase_avro_table",
"hbase.mapred.output.outputtable" = "hbase_avro_table",
"hbase.struct.autogenerate"="true"); |
The important properties to note are the following three:
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"test_col_fam.test_col.serialization.type" = "avro" |
This property tells Hive that the given column under the given column family is an Avro column, so Hive needs to deserialize it accordingly.
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"test_col_fam.test_col.avro.schema.url" = "hdfs://testcluster/tmp/schema.avsc" |
Using this property you specify where the reader schema is for the column that will be used to deserialize. This can be on HDFS like mentioned here, or provided inline using something like "test_col_fam.test_col.avro.schema.literal"
property. If you have a custom store where you store this schema, you can write a custom implementation of AvroSchemaRetriever and plug that in using the "avro.schema.retriever property"
using a property like "test_col_fam.test_col.avro.schema.retriever"
. You would need to ensure that the jar with this custom class is on the Hive classpath. For a usage discussion and links to other resources, see HIVE-6147.
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"hbase.struct.autogenerate" = "true" |
Specifying this property lets Hive auto-deduce the columns and types using the schema that was provided. This allows you to avoid manually creating the columns and types for Avro schemas, which can be complicated and deeply nested.
Put Timestamps
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As of Hive 0.9.0 |
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