I have a hive table over an accumulo table (because we need cell level security):
CREATE TABLE testtable(rowid string, value string)
STORED BY 'org.apache.hadoop.hive.accumulo.AccumuloStorageHandler'
WITH SERDEPROPERTIES('accumulo.columns.mapping' = ':rowid,c:value') TBLPROPERTIES ('accumulo.table.name' = 'testtable');
If i have a value which contains "/n" it conflicts with the default hive line break property which is also "/n".
for example:
accumulo insert: insert 1 c value line\x0Abreak
hive select: select rowid, value, row_number() over (order by null) as rank from testtable;
you will get back two rows instead of one.
| rowid | value | rank |
+---------+--------+-------+
| 2 | line | NULL |
| break | 1 | NULL |
Is there any idea how can I avoid this? Thank you for all the help!
That seems very unexpected (as the author of the AccumuloStorageHandler), but maybe I just don't know something that Hive is trying to do?
I'd file a JIRA issue for Hive over at https://issues.apache.org/jira/secure/CreateIssue!default.jspa. Feel free to mention me and I can try to help write a test and get to the bottom of it.
Related
I am using Impala for querying parquet-tables and cannot find a solution to increment an integer-column ranging from 1..n. The column is supposed to be used as ID-reference. Currently I am aware of the uuid() function, which
Returns a universal unique identifier, a 128-bit value encoded as a string with groups of hexadecimal digits separated by dashes.
Anyhow, this is not suitable for me since I have to pass the ID to another system which requests an ID in style of 1..n. I also already know that Impala has no auto-increment-implementation.
The desired result should look like:
-- UUID() provided as example - I want to achieve the `my_id`-column.
| my_id | example_uuid | some_content |
|-------|--------------|--------------|
| 1 | 50d53ca4-b...| "a" |
| 2 | 6ba8dd54-1...| "b" |
| 3 | 515362df-f...| "c" |
| 4 | a52db5e9-e...| "d" |
|-------|--------------|--------------|
How can I achieve the desired result (integer-ID ranging from 1..n)?
Note: This question differs from this one which specifically handles Kudu-tables. However, answers should be applicable for this question as well.
Since other Q&A's like this one only came up with uuid()-alike answers, I put some thought in it and finally came up with this solution:
SELECT
row_number() OVER (PARTITION BY "dummy" ORDER BY "dummy") as my_id
, some_content
FROM some_table
row_number() generates a continuous integer-number over a provided partition. Unlike rank(), row_number() always provides an incremented number on its partition (even if duplicates occur)
PARTITION BY "dummy" partitions the entire table into one partition. This works since "dummy" is interpreted in the execution graph as temporary column yielding only the String-value "dummy". Thus, also something analog to "dummy" works.
ORDER BY is required in order to generate the increment. Since we don't care about the order in this example (otherwise just set your respective column), also use the "dummy"-workaround.
The command creates the desired incremental ID without any nested SQL-statements or other tricks.
| my_id | some_content |
|-------|--------------|
| 1 | "a" |
| 2 | "b" |
| 3 | "c" |
| 4 | "d" |
|-------|--------------|
I used Markus's answer for a large partitioned table and found that I was getting duplicate ids. I think the ids were only unique within their partition; possibly PARTITION BY "dummy" leads Impala to think that each partition can execute row_number() on its own. I was able to get it working by specifying an actual column to order by and no partition by:
SELECT
row_number() OVER (ORDER BY actual_column) as my_id
, some_content
FROM some_table
It doesn't seem to matter whether the values in the column are unique (mine weren't), but using the actual partition key might result in the same issue as the "dummy" column.
Understandably, it took a lot longer to run than the dummy version.
My table is stud.
+-----+------+-------+
| no | name | grade |
+-----+------+-------+
| 101 | naga | A |
| 102 | raj | A |
| 103 | john | A |
+-----+------+-------+
The query I'm using is:
SELECT * FROM stud WHERE no = 101 AND grade = 'A'.
If am using single record buffering, how much data is being stored in the buffer area?
This query doesn't do anything. There is no "into" clause. meaning it wont store anything selected.
You are probably looking to do something like this....
SELECT * FROM stud into wa_stud WHERE no = 101 AND grade = 'A'.
"processing of each single row is performed here
endselect.
or perhaps something like this, where only 1 row (the first rows ordered by primary key) is selected...
select single * from stud into wa_stud where no = 101 and grade = 'A' .
or perhaps you want everything brought in to a table, meaning number and grade does not include the full primary key.
select * from stud into table it_stud where no = 101 and grade = 'A'.
this is from ABAP Keyword documentation in SE38:
SAP Buffer - Single Record Buffering
Only those rows in the table are buffered that are actually accessed.
This requires less space in the buffer than when using generic or full
buffering. On the other hand, more administration work is required and
significantly more direct database accesses.
So since your query returns a single record (based on the data you displayed) it should just get one row and hold in the buffer.
I'd suggest looking at SAP help and Google - also have a look at SELECT SINGLE and incompletely specified keys - there used to be a problem with the buffer being bypassed in some situations - have a read for reference.
Can data in Hive be transposed? As in, the rows become columns and columns are the rows? If there is no function straight up, is there a way to do it in a couple of steps?
I have a table like this:
| ID | Names | Proc1 | Proc2 | Proc3 |
| 1 | A1 | x | b | f |
| 2 | B1 | y | c | g |
| 3 | C1 | z | d | h |
| 4 | D1 | a | e | i |
I want it to be like this:
| A1 | B1 | C1 | D1 |
| x | y | z | a |
| b | c | d | e |
| f | g | h | i |
I have been looking up other related questions and they all mention using lateral views and explode, but is there a way to selectively choose columns for lateral(ly) view(ing) and explod(ing)?
Also, what might be the rough process to achieve what I would like to do? Please help me out. Thanks!
Edit: I have been reading this link: https://cwiki.apache.org/Hive/languagemanual-lateralview.html and it shows me half of what I want to achieve. The first example in the link is basically what I'd like except that I don't want the rows to repeat and want them as column names. Any ideas on how to get the data to a form such that if I do an explode, it would result in my desired output, or the other way, ie, explode first to lead to another step that would then lead to my desired output table. Thanks again!
I don't know of a way out of the box in hive to do this, sorry. You get close with explode etc. but I don't think it can get the job done.
Overall, conceptually, I think it's hard to a transpose without knowing what the columns of the destination table are going to be in advance. This is true, in particular for hive, because the metadata related to how many columns, their types, their names, etc. in a database - the metastore. And, it's true in general, because not knowing the columns beforehand, would require some sort of in-memory holding of data (ok, sure with spills) and users may need to be careful about not overflowing the memory and such (just like dynamic partitioning in hive).
In any case, long story short, if you know the columns of the destination table beforehand, life is good. There isn't a set command in hive per se, to the best of my knowledge, but you could use a bunch of if clauses and case statements (ugly I know, but that's how I have done the same in the past) in the select clause to transpose the data. Something along the lines of SQL - How to transpose?
Do let me know how it goes!
As Mark pointed out there's no easy way to do this in Hive since PIVOT doesn't present in Hive and you may also encounter issues when trying to use the case/when 'trick' since you have multiple values (proc1,proc2,proc3).
As for testing purposes, you may try a different approach:
select v, o1, o2, o3 from (
select k,
v,
LEAD(v,3) OVER() as o1,
LEAD(v,6) OVER() as o2,
LEAD(v,9) OVER() as o3
from (select transform(name,proc1,proc2,proc3) using 'python strm.py' AS (k, v)
from input_table) q1
) q2 where k = 'A1';
where strm.py:
import sys
for line in sys.stdin:
line = line.strip()
name, proc1, proc2, proc3 = line.split('\t')
print '%s\t%s' % (name, proc1)
print '%s\t%s' % (name, proc2)
print '%s\t%s' % (name, proc3)
The trick here is to use a python script in the map phase which emits each column of a row as distinct rows. Then every third (since we have 3 proc columns) row will form the resulting row which we get by peeking forward (lead).
However, this query does the job, it has the drawback that as the input grows, you need to peek the next 3rd element in the query which may lead to performance hit. Anyway you may evaluate it for testing purposes.
First: I'm using Access 2010.
What I need to do is pull everything in a field out that is NOT a certain string. Say for example you have this:
00123457*A8V*
Those last 3 characters that are bolded are just an example; that portion can be any combination of numbers/letters and from 2-4 characters long. The 00123457 portion will always be the same. So what I would need to have returned by my query in the example above is the "A8V".
I have a vague idea of how to do this, which involved using the Right function, with (field length - the last position in that string). So what I had was
SELECT Right(Facility.ID, (Len([ID) - InstrRev([ID], "00123457")))
FROM Facility;
Logically in this mind it would work, however Access 2010 complains that I am using the Right function incorrectly. Can someone here help me figure this out?
Many thanks!
Why not use a replace function?
REPLACE(Facility.ID, "00123457", "")
You are missing a closing square bracket in here Len([ID)
You also need to reverse this "00123457" in InStrRev(), but you don't need InStrRev(), just InStr().
If I understand correctly, you want the last three characters of the string.
The simple syntax: Right([string],3) will yield the results you desire.
(http://msdn.microsoft.com/en-us/library/ms177532.aspx)
For example:
(TABLE1)
| ID | STRING |
------------------------
| 1 | 001234567A8V |
| 2 | 008765432A8V |
| 3 | 005671234A8V |
So then you'd run this query:
SELECT Right([Table1.STRING],3) AS Result from Table1;
And the Query returns:
(QUERY)
| RESULT |
---------------
| A8V |
| A8V |
| A8V |
EDIT:
After seeing the need for the end string to be 2-4 characters while the original, left portion of the string is 00123457 (8 characters), try this:
SELECT Right([Table1].[string],(Len([Table1].[string])-'8')) AS Result
FROM table1;
I have to move words table's data to another tables.
For example words table is :
------------------------------
| word | type |
|------------------|---------|
| car | NA |
| home | NA |
| question | PR |
------------------------------
I have to move this data by length . For example , car's length is 3 , and car will move to 3-char table (with type column). And question will moved to 8-char .
How can i do it with SQL commands .
Sort of an incomplete question, but something like this might help point you in the right direction:
INSERT INTO words_3char SELECT word FROM all_words WHERE LENGTH(word)=3;
DELETE FROM all_words WHERE LENGTH(word)=3;
I'm not going to ask why you need to do all this moving around, but I'm not sure its a good idea. Assuming it is, take a look at the Length() function for mysql and then try something like this.
Insert into table_Char3(Word) Values (
Select Word from Words where Length(word) = 3)
You can move them to new tables like this
create table word1char as select word from words where length(trim(word)) = 1
..
create table word3chars as select word from words where length(trim(word)) = 3