hive query optimization

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Connect to hive in PHP to execute SQL query

Conditions for using PHP to connect to hive 1. Install Thrift #./Configure -- without-Ruby # Make make install If libevent-devel is not installed, install the two dependent libraries Yum-y install libevent-devel first. Start hive thrift after installation #./Hive -- service hiveserver>/dev/null 2>/dev/null Check whether the default port 10000 of h

The execution process of hive query on MapReduce

The hive query is first converted to a physical query plan, and the physical query plan typically contains multiple mapreduce jobs, and the output of one mapreduce job can be used as input to another mapreduce job. The MapReduce job designed by Hive for

The query result of the imported file created in the hive table is null.

Tags: hadoop data hive When creating a table, hive will specify a delimiter. For example, it is set to tab to separate attribute columns \ n to separate records. However, if the format of the document we uploaded is not as follows, the record is saved but the query result is indeed a column of null. The format of the TXT file to be uploaded,

Increased hive optimization reduces map count

you to use multiple map tasks to complete.Set mapred.reduce.tasks=10;CREATE TABLE A_1 asSELECT * from aDistribute by RAND (123);This will be a table of records, randomly scattered into the a_1 table containing 10 files, and then replaced by a_1 in the SQL table A, you will use 10 map tasks to complete.Each map task handles more than 12M (millions of records) of data, which is certainly much more efficient.Looks like these two kinds of contradictions, one is to merge small files, one is to take

Using hive query for error in Hadoop cluster

Today, when using hive to query the maximum value of a certain analysis data, there is a certain problem, in hive, the phenomenon is as follows:caused by:java.io.filenotfoundexception://http://slave1:50060/tasklog?attemptid=attempt_201501050454_0006_m_00001_1Then take a look at the Jobtracker log:2015-01-05 21:43:23,724 INFO Org.apache.hadoop.mapred.jobinprogress

009-hadoop Hive SQL Syntax 4-DQL operations: Data Query SQL

statement can use a regular expression to make a column selection, and the following statement queries all columns except DS and HR:SELECT ' (ds|hr)? +.+ ' from TestFor exampleSearch by First piecehive> SELECT A.foo from invites a WHERE a.ds= ' To output query data to a directory:hive> INSERT OVERWRITE DIRECTORY '/tmp/hdfs_out ' SELECT a.* from invites a WHERE a.ds= ' output query results to a local direct

Hive Common Query Statements

Querying for different Androidid Select COUNT (Distinct androidid) from table where dt= ' date ' and androidid are not null and Androidid and Androidid Query the total number of unique users, because a user is determined to have a unique value of four attributes, so add and then go back Hive> Select COUNT (Distinct concat (NVL (IDFA, '), Nvl (Mac, '), NVL (IMEI, '), NVL (Androidid, '))) from table wheRe

Sub-query in hive change JOIN operation

These subqueries can be executed in databases such as Oracle and MySQL, but are not supported in hive, but we can change these query statements to join operations: -- 1. Subquery Select * from a a where a.update_time = (select min (b.update_time) from a B) -- 2.in operation Select * from a a where a.dept = ' IT ' and Change to join operation as follows: -- 1 Select

Hive Learning Notes-Advanced query

same key is aggregated together, and subsequent must be the aggregation operation Order BY and Sort by Order by ensures global order Sort by simply ensures that each reduce has an ordered output, and if there is only one reduce, the same as the order by effect Application Scenarios Too many small files (control the number of output files by the number of reduce) File is super large File size of map output is not uniform The file size of the reduce output is not uniform Cluster by Bring togeth

Spark-1.3.1 and hive integration for query analysis

In big data scenarios, using hive to do query statistical analysis should be aware that the computational delay is very large, may be a very complex statistical analysis needs, need to run more than 1 hours, but compared to the use of MySQL and other relational database analysis, the execution speed much faster. Using HIVEQL to write SQL-like query parsing statem

Hue 3.11.0 in hive query integrated hbase table times wrong, solve

Hue 3.11.0 in hive query integrated hbase table times wrong, solve Bad status for Request Tfetchresultsreq (fetchtype=0, Operationhandle=toperationhandle (Hasresultset=true, Modifiedrowcount=none, Operationtype=0, Operationid=thandleidentifier (secret= ' bzt\x1b\x17\xf6af\xa3\xd7n\xe39\ Xf5\xe3~ ', guid= ' \x9fxq/9#g\x12\xb1\xaf\xf5t\xb9u\xcc\x96 '), orientation=4, maxrows=100): TFetchResultsResp ( Status

Where and group by statements in a HIVE-2.HIVEQL query

1. Where statement Query the list of English scores greater than or equal to 70: Select Name,ceil (Salary) as salary,age from employees where score[' 中文版 ']>=70; Output Result: Name Salary Age WANGWU1 5500 20 WANGWU3 8400 20 Wangwu4 8400 20 Use the like statement to blur the view of list information Select Name,ceil (Salary) as salary,age,address.province from employees where address.province like ' river% '; Output Result: Name Salary Age Province

Hive error when executing query statement

Hive Error when executing query statement: org.apache.hadoop.ipc.RemoteException:java.io.IOException:java.io.IOException: Hive> Select product_id, track_time from Trackinfo limit 5; Total MapReduce jobs = 1 Launching Job 1 out of 1 number of reduce tasks are set to 0 since there ' s no reduce operator Org.apache.hadoop.ipc.RemoteException:java.io.IOExcepti

Hive Web query statement insert MySQL database times wrong

Recently, users have complained that the hive Web client does not return results to the front end after submitting some queries, such as a statement that joins five tables, and only one join is removed. Query to write a temporary table, and then join the last table to do. I later debug, the Discovery statement is really successful execution, and the result file has been dump into the

Hive Query Summary

First look at the query syntax of the Xia Guan Network: [With Commontableexpression (, commontableexpression) *] (Note:only available starting with Hive 0.13.0) SELECT [All | DISTINCT] select_expr, select_expr, ... From Table_reference [WHERE where_condition] [GROUP by col_list] [ ORDER by col_list] [CLUSTER by Col_ List | [Distribute by col_list] [SORT by col_list] ] [LIMIT number] WHE

Mysql uses indexes for query optimization and mysql index Query Optimization

Mysql uses indexes for query optimization and mysql index Query Optimization The purpose of indexing is to improve the query efficiency. It can be analogous to a dictionary. If you want to query the word "mysql", you must locate t

SQL optimization--Logical optimization--sub-query optimization (MySQL)

result set type returned by the subquery is a simple value. b) Single-row sub-query. The result set type returned by the subquery is 0 or one unit group. Similar to the scalar subquery, but may return 0 tuples. c) Multiline single-row subquery. The result set type returned by a subquery is a multi-tuple but has only one simple column. d) Table sub-

Database optimization tutorial (3) Slow query of records and database optimization tutorial Query

Database optimization tutorial (3) Slow query of records and database optimization tutorial Query1. Slow query foundIn the previous section, we made data preparation for slow queries. This section allows us to find slow queries and record them to files. 3. Slow query of reco

Database optimization tutorial (3) Slow query of records and database optimization tutorial Query

Database optimization tutorial (3) Slow query of records and database optimization tutorial Query1. Slow query foundIn the previous section, we made data preparation for slow queries. This section allows us to find slow queries and record them to files. 3. Slow query of reco

SQL Server query performance optimization-index creation principles (ii) SQL Server query performance optimization-index creation principles (I)

Yesterday's SQL Server query performance optimization-index creation principle (I) mainly introduced the principle. today are some of the main principles and checks the created indexes. Iii. indexing principles In general, building indexes depends on the data usage scenarios. In other words, which SQL statements are commonly used to access data? Are these statements missing indexes (or there may be too many

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