# Concurrent read value if thread process happen

**URL:** https://discourse.hibernate.org/t/concurrent-read-value-if-thread-process-happen/3240
**Category:** Hibernate ORM
**Created:** [September 18, 2019, 10:43am UTC](https://discourse.hibernate.org/t/concurrent-read-value-if-thread-process-happen/3240 "2019-09-18T10:43:00Z")
**Posts on this page:** 2
**Page:** 1

<div class="post-metadata">

### Author: ![blinkbink](https://avatars.discourse-cdn.com/v4/letter/b/22d042/32.png) [@blinkbink](https://discourse.hibernate.org/u/blinkbink)
#### Post date: [September 18, 2019, 10:43am UTC](https://discourse.hibernate.org/t/concurrent-read-value-if-thread-process-happen/3240/1 "2019-09-18T10:43:00Z")

</div>

Hello, i’m new using hibernate. I have this situation. The flow is sum all amount on single field “amount” then store the value to next current balance on Table InvoiceItems

```auto
amount | type | account_id | current_balance
   100 topup A 100
    -1 usage A 99
    5 topup B 5
   -3 usage B 2
   -3 usage A 96

```

then i sum the value of account A with this query function :

```auto
> public BigDecimal getBalance(String accountid) {
> return (BigDecimal)this.session.createQuery("select SUM(amount) from InvoiceItems WHERE account_id = '" + accountid + "' ").setLockMode(accountid, LockMode.OPTIMISTIC).getSingleResult();
> }

```

another class call query function :

```auto
BigDecimal balance = ido.getBalance(accountid);

InvoiceItems invoiceItemsUSAGE = new InvoiceItems();

invoiceItemsUSAGE.setAmount(BigDecimal.valueOf(jsonRecv.getLong("amount")));
invoiceItemsUSAGE.setType("USAGE");	
invoiceItemsUSAGE.setCurrent_balance(balance.subtract(BigDecimal.valueOf(jsonRecv.getLong("amount"))));

db.session().save(invoiceItemsUSAGE);

tx.commit();

```

the movement of current balance is fine, but when thread process like 3 thread almost run same time (just different .121 millisecond) the current\_balance movement not consistent, it’s like the process read same value before the transaction commit.

```auto
amount | type | account_id | current_balance | time
   100 topup A 100 2019-09-18 17:21:40.015714
    -1 usage A 99 2019-09-18 18:21:41.011114
    5 topup B 5 2019-09-18 19:23:30.013314
   -3 usage B 2 2019-09-18 20:34:40.022714
   -3 usage A 96 2019-09-18 21:21:40.015714
   -1 usage A 95 2019-09-18 22:21:40.115714
   -1 usage A 95 2019-09-18 22:21:40.121714
   -1 usage A 95 2019-09-18 22:21:40.132114
   -1 usage A 95 2019-09-18 22:21:40.145114
   -1 usage A 91 2019-09-18 23:55:40.153714
   -1 usage A 90 2019-09-18 24:41:40.015714

```

i have try with lock on query

```auto
> public BigDecimal getBalance(String accountid) {
> return (BigDecimal)this.session.createQuery("select SUM(amount) from InvoiceItems WHERE account_id = '" + accountid + "' ").setLockMode(accountid, LockMode.OPTIMISTIC).getSingleResult();
> }

```

any clue ?

---

<div class="post-metadata">

### Author: ![blinkbink](https://avatars.discourse-cdn.com/v4/letter/b/22d042/32.png) [@blinkbink](https://discourse.hibernate.org/u/blinkbink)
#### Post date: [September 19, 2019, 12:49pm UTC](https://discourse.hibernate.org/t/concurrent-read-value-if-thread-process-happen/3240/2 "2019-09-19T12:49:46Z")

</div>

i have try with set the postgresql database with :

```auto
ALTER DATABASE billing SET default_transaction_isolation = 'serializable';
ALTER USER postgres SET default_transaction_isolation = 'serializable'

```

and set connection.isolation to 8, but when hit with thread got error :

> ERROR: could not serialize access due to read/write dependencies among transactions  
> Detail: Reason code: Canceled on identification as a pivot, during conflict out checking.  
> Hint: The transaction might succeed if retried.

still not correct result, any clue ?