I am using hadoop 2.7.3 and hive 2.1.1.
I had some 8-9 file in HDFS. I created one internal hive table. I loaded first of those 8 files in that table. Did some operation on that data.
After that I loaded the second of those files by overwriting into that table.
load data inpath '/path/path1/first.csv' into table ABC;
load data inpath '/path/path1/second.csv' overwrite into table ABC;
Did some operation on second data.
I then loaded third file and so on till the last file by using "overwrite into" .
Now, I see all those files are not there in there original location. Also, at /user/hive/warehouse/ABC only the last of the files is there.
Where did those previous files go? Are they lost because of overwriting into hive table? I did "hdfs dfs -ls -R / | grep "filename" but could not find my files.
LOAD DATA INPATH will move (not copy) the file from the source HDFS path to the table warehouse path.
OVERWRITE will delete the files (if HDFS Trash is enabled, move the files to Trash) that already exist in the table and replace with the files given in the path.
LOAD DATA LOCAL INPATH copies the files.
LOAD DATA INPATH moves the files.
overwrite deletes existing files before moving in new files.
Related
Just a simple question, I'm new in Impala.
I want to load data from the HDFS to my datalake using impala.
So I have a csv this_is_my_data.csv and what I want to do is load the file without specify all the extension, I mean something like the following:
LOAD DATA INPATH 'user/myuser/this_is.* INTO TABLE my_table
This is, a string starting with this_is and whatever follows.
If you need some additional information, please let me know. Thanks in advance.
The documentation says:
You can specify the HDFS path of a single file to be moved, or the
HDFS path of a directory to move all the files inside that directory.
You cannot specify any sort of wildcard to take only some of the files
from a directory.
The workaround is to put your files into table directory using mv or cp command. Check your table directory using DESCRIBE FORMATTED command and run mv or cp command (in a shell, not Impala of course):
hdfs dfs -mv "user/myuser/this_is.*" "/user/cloudera/mytabledir"
Or put files you need to load into some directory first then load all the directory.
When I run the create external table query, I have to provide a directory for the 'Location' attribute. But if the directory I point to has more than one file, then it reads both files. For example, if I put LOCATION 'dir1/', and dir1 contains file1 and file2, both files will be read.
To avoid this, I want to point to a single file. When I tried LOCATION 'dir1/file1', it gave me an error that the file path is not a directory or unable to create one. Is there a way to point to just the single file?
If You want to load data from HDFS so try this
LOAD DATA INPATH '/user/data/file1' INTO TABLE table1;
And if you want to load data from local storage so,
LOAD DATA LOCAL INPATH '/data/file1' INTO TABLE table1;
I have a large log file which I loaded in to HDFS. HDFS will replicate to different nodes based on rack awareness.
Now I load the same file into a hive table. The commands are as below:
create table log_analysis (logtext string) STORED AS TEXTFILE
LOCATION '/user/hive/warehouse/';
LOAD DATA INPATH '/user/log/apache.log' OVERWRITE INTO TABLE log_analysis;
Now when I go and see the '/user/hive/warehouse/' directory there is a table file and copying it to local, it has all the log file data.
My question is: the existing file in HDFS is replicated. Then loading that file in hive table, stored on HDFS also gets replicated.
Is that not the same file stored 6 times (assuming that replication factor is 3) ? That would be such a waste of resources.
Correct, In case you are loading the data from HDFS , the data moves from HDFS to the /user/hive/warehouse/yourdatabasename/tablename.
Your question indicates that you have created an INTERNAL table using hive and you are loading data into HIVE table from HDFS location.
When you load data into an internal table using LOAD DATA INPATAH command, It moves data from the primary location to another location. In your case, it should be /user/hive/warehouse/log_analysis. So basically it provides new address and new HDFS location of the data and you won't be seeing anything in the previous location.
When you move data from one location to another location on HDFS. NameNode receives a new location of the data and it deletes all old metadata for that data. Hence there won't be any duplicate information of the data and the data and there will be only 3 replication and it will be stored only 3 times.
I hope it clear to you.
I'm using the hortonworks's Hue (more like a GUI interface that connects hdfs, hive, pig together)and I want to load the data within the hdfs into my current created table.
Suppose the table's name is "test", and the file which contains the data, the path is:
/user/hdfs/test/test.txt"
But I'm unable to load the data into the table, I tried:
load data local inpath '/user/hdfs/test/test.txt' into table test
But there's error said can't find the file, there's no matching path.
I'm still so confused.
Any suggestions?
Thanks
As you said "load the data within the hdfs into my current created table".
But in you command you are using :
load data local inpath '/user/hdfs/test/test.txt' into table test
Using local keyword it looks for the file in your local filesystem. But you file is in HDFS.
I think you need to remove local keyword from you command.
Hope it helps...!!!
Since you are using the hue and the output is showing not matching path. I think you have to give the complete path.
for example:
load data local inpath '/home/cloudera/hive/Documents/info.csv' into table tablename; same as you can give the complete path where the hdfs in which the document resides.
You can use any other format file
remove local keyword as ur referring to local file system
I'm learning Hive's DML operations.
In this tutorial https://cwiki.apache.org/confluence/display/Hive/GettingStarted#GettingStarted-RunningHive
there is a example,
hive> LOAD DATA LOCAL INPATH './examples/files/kv1.txt' OVERWRITE INTO TABLE pokes;
I want to ask what does the current path "./" refer to in this case?
And there is another example,
hive> LOAD DATA INPATH '/user/myname/kv2.txt' OVERWRITE INTO TABLE invites PARTITION (ds='2008-08-15');
It said Hive loads data from hdfs in this case, then I am confused about what is the root path of hdfs on local file system?
It means starting from your home directory in the local path. You have to have the hdfs dfs prefix to each command to move stuff in the hdfs path.