Hypertable is an open source project based on published best practices and our own experience in solving large-scale data-intensive tasks. Our goal is nothing. Modeled after Bigtable. ➢ Implemented in C++. ➢ Project Started in March ➢ Runs on top of HDFS. ➢ Thrift Interface for all popular languages. ○ Java. hypertable> create namespace “Tutorial”;. hypertable> use Tutorial;. create table. hypertable> CREATE TABLE QueryLogByUserID (Query.
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For that, we assume you have the example data in the file query-log. This will cause the TextTableInputFormat class to produce an additional field field 0 that represents the timestamp as nanoseconds since the epoch. Value indices index hypertab,e value data and qualifier indices index column qualifier data. For example, assuming there are three slave servers, the following diagram shows what the system might look like over time.
This timestamp dimension can be thought of as representing different versions of each table cell, hjpertable illustrated in the following diagram.
This function can also be used through the Thrift interface.
The sys namespace is used by the Hypertable system and should not be used to contain user tables. You cannot mix-and-match the two.
To run a MapReduce job over a subset of columns from the input table, specify a comma separated list of columns in the hypertable. Select the title column of all rows whose row key is greater than ‘BVWE0’ and that contain an info: The following diagram illustrates how a relational database table might be laid out on disk.
This page provides a brief overview of Hypertaable, comparing it with a relational database, highlighting some of its unique features, and illustrating how it scales. Unique cells can be used whenever an application wants to make sure that there can never be more than one cell value in a column family.
In this section, we walk you through an example MapReduce program, WikipediaWordCount, that tokenizes articles in a table called wikipedia that has been loaded with a Wikipedia dump.
In the schema, the rowkey is a URL and the title, description and topic are column families. The following is a list of some of the main differences. NULL values are usually represented with a special marker e. A relational database assumes that each column defined in the table schema will have a value for each row that is present in the table.
In this example, we’ll be running a Hadoop Streaming MapReduce job that uses a Bash script as the mapper and a Bash script as the reducer. In this example, we’ll be running the WikipediaWordCount program which is included in the hypertable-examples. Select the title column of all rows that contain an info: These processes manage ranges of table data and run on all slave server machines in the cluster.
The QueryTime field is used as the internal cell timestamp. Over time, Hypertable will break these tables into ranges and distribute them to what are known as RangeServer processes. The following table lists the job configuration properties that are used to specify, among other things, the input table, output table, and scan specification.
This is why we imported the data into a second table QueryLogByTimestamp.
To inspect this file we first quit out of the Hypertable command line interpreter and then use the zcat program requires gzip package to display the contents of query-log. The next step is to make sure Hypertable is properly installed see Installation and then launch the service.
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The row key is formulated by zero-padding the UserID field out to nine digits and concatenating the QueryTime field. The timestamp can be supplied by the application at insert time, or can be auto-generated default. For an explanation of namespaces see Namespaces.
Hypertable contains support for secondary indices. You’ll need to download the data from http: Hypertable extends the traditional two-dimensional table model by adding a third dimension: To filter the input table with a timestamp predicate, specify the timestamp predicate in the hypertable. Exit the hypertable shell and download the dataset, which is in the.
Let’s say the system has been loaded with the following two tables, a session ID table and a crawl database table. Then create a scanner, fetch the cell and verify that it was written correctly.
Adding more capacity is a simple matter of adding new commodity class servers and starting RangeServer processes on the new machines. The next example shows how to query for data where the description contains the tutotial game followed by either foosball or halo:. All of the example queries show were run against a table with the following schema and loaded with products. In this example we create a table of counters called counts that contains a single column family url that acts as an atomic counter for urls.
For example, the following query will not leverage the secondary indexes and will result int a full table scan:. In this tutorial we will be loading data into, and querying data from, two separate tables. Remember that the row key is the hypertablw of the user ID and the timestamp which is why we need to use the starts with operator. Each unique word in the article turns into a qualified column and the value is the number of times the word appears in the article.
Next, jump back into the Hypertable command line interpreter and create the wikipedia table by executing the HQL commands show below. To open the root namespace issue the following HQL command:.
First, open tutogial root namespace. It reads the article column, tokenizes it, and populates the word column of the same table. The interval is constrained by the value of the config property Hypertable.