Export cassandra query result to a csv file

问题

I'm new in cassandra, and I have to export the result of a specific query to a csv file.

I found the COPY command, but (from what I understand) it allows you only to copy an already existing table to a csv file, and what I want is to copy directly the stdout of my query to the csv file. is there any way to do it with COPY command or with another way ?

My command is style (select column1, column2 from table where condition = xy) and I'm using cqlsh.

回答1:

If you don't mind your data using a pipe ('|') as a delimiter, you can try using the -e flag on cqlsh. The -e flag allows you to send a query to Cassandra from the command prompt, where you could redirect or even perform a grep/awk/whatever on your output.

$ bin/cqlsh -e'SELECT video_id,title FROM stackoverflow.videos' > output.txt
$ cat output.txt

 video_id                             | title
--------------------------------------+---------------------------
 2977b806-df76-4dd7-a57e-11d361e72ce1 |                 Star Wars
 ab696e1f-78c0-45e6-893f-430e88db7f46 | The Witches of Whitewater
 15e6bc0d-6195-4d8b-ad25-771966c780c8 |              Pulp Fiction

(3 rows)

Older versions of cqlsh don't have the -e flag. For older versions of cqlsh, you can put your command into a file, and use the -f flag.

$ echo "SELECT video_id,title FROM stackoverflow.videos;" > select.cql
$ bin/cqlsh -f select.cql > output.txt

From here, doing a cat on output.txt should yield the same rows as above.

回答2:

Use CAPTURE command to export the query result to a file.

cqlsh> CAPTURE
cqlsh> CAPTURE '/home/Desktop/user.csv';
cqlsh> select *from user;
Now capturing query output to '/home/Desktop/user.csv'.

Now, view the output of the query in /home/Desktop/user.csv

Use DevCenter and execute a query. Right click on the output and select "Copy All as CSV" to paste the output in CSV.

回答3:

I just wrote a tool to export CQL query to CSV and JSON format. Give it a try :)

https://github.com/tenmax/cqlkit

回答4:

I believe DevCenter also allows you to copy to CSV. http://www.datastax.com/what-we-offer/products-services/devcenter

回答5:

In windows, double quotes should be used to enclose the CQL.

cqlsh -e"SELECT video_id,title FROM stackoverflow.videos" > output.txt

回答6:

If I am understanding correctly you want to redirect your output to stdout?

Put your cql command in a file. My files is called select.cql and contents are:

select id from wiki.solr limit 100;

Then issue the following and you get it to stdout:

cqlsh < select.cql

I hope this helps. From there on you can pipe it and add commas, remove headers etc.

回答7:

Cannot comment... To deal with "MORE" issue when there are more than 100 rows, simply add "paging off" before the SQL.

Something like

$ bin/cqlsh -e'PAGING OFF;SELECT video_id,title FROM stackoverflow.videos' > output.txt

This will cause a little messy at the beginning of the output file but can easily be removed afterwards.

回答8:

You can use the COPY command to create the CSV file. e.g. copy table with selected columns. Columns are optional, if you select them, every column will be picked.

COPY TABLE (COL1, COL2) TO 'filename.csv' HEADER=TRUE/FALSE

For more reference https://docs.datastax.com/en/cql/3.3/cql/cql_reference/cqlshCopy.html

回答9:

With bash:

If you need to query the data (not possible with COPY TO) and if you need the final product to be importable (ie with COPY FROM):

cqlsh -e "SELECT * FROM bar WHERE column = 'baz' > raw_output.txt

Then you can reformat the output with sed

sed 's/\ //g; /^----.*/d; /^(/d; /^\s*$/d;' raw_output.txt | tee clean_output.csv

Which pretty much says

sed 'remove spaces; remove the column boarder; remove lines beginning with (COUNT X); and remove blank lines' | write output into clean_output.csv

The sed regexp's could be cleaned up to better suite your specific case, but thats the general idea.

回答10:

The person asking asked for CSV not text.

I did this hack get my results. It worked for me and I moved on with my day.

来源：https://stackoverflow.com/questions/26909408/export-cassandra-query-result-to-a-csv-file

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cassandra

cqlsh