How to create parallel connections and queries to db in bash script - linux

Question

I have an oracle db on my Linux machine.
A single sql query (1 connection) via bash is as follows:
su - oracle
sqlplus <dbuser>/<dbpass>
select * from cat;
exit
I'm trying to run parallel queries via bash, the following script is for running 10000 connections in parallel (Correct me if i'm wrong):
for i in $(seq 1 10000); do echo "select * from <tableName>;" | sqlplus <dbuser>/<dbpass>&done
I would like to make this code more robust and flexible, for the sake of example i want to add a sleep between each of the following command:
Create a connection
Create a table (Unique to this connection, i as index for example)
Select data from the table
Close the connection
The following code is my attempt of doing so: (Not working)
for i in $(seq 1 10000);
do
echo "CREATE TABLE test+i (id NUMBER NOT NULL);"
sleep 2
echo "select * from test+i"
sleep 2
echo "DROP TABLE test+i" | sqlplus <dbuser>/<dbpass>&
done
1) Syntactically, how should i write it?
2) How can i know how many queries/connections succeeded and how many failed?
3) How can i know how many connections actually ran in parallel

Answer 1

1) you can use ( and ) to group command into subshells, and send them background:
for i in $(seq 1 10000);
do
echo "CREATE TABLE test_$i (id NUMBER NOT NULL);
!sleep 2
select * from test_$i;
!sleep 2
DROP TABLE test_$i;" | sqlplus <dbuser>/<dbpass> &
done
2) you can set up error handling after each sqlplus call (examine output or exit value)
echo "CREATE TABLE test_$i (id NUMBER NOT NULL);" | sqlplus <dbuser>/<dbpass> 2>&1 | grep -i error
3) you can use the jobs command to examine how many job is running in the background:
> sleep 100 &
[1] 31642
> jobs
[1]+ Running sleep 100 &

Answer 2

10000 jobs in parallel will often cause overflow. By setting 'WHENEVER SQLERROR EXIT SQL.SQLCODE' sqlplus will return an error, if the SQL fails. GNU Parallel can then re-run the query.
my.log will show if the query failed after rerunning 3 times.
doit() {
i=$1
(echo "WHENEVER SQLERROR EXIT SQL.SQLCODE CREATE TABLE test$i (id NUMBER NOT NULL);"
sleep 2
echo "WHENEVER SQLERROR EXIT SQL.SQLCODE select * from test$i;"
sleep 2
echo "WHENEVER SQLERROR EXIT SQL.SQLCODE DROP TABLE test$i;") |
sqlplus <dbuser>/<dbpass>
}
export -f doit
seq 1 10000 | parallel --joblog my.log -j0 --retries 3 doit