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https://issues.apache.org/jira/browse/CASSANDRA-18465?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jacek Lewandowski updated CASSANDRA-18465:
------------------------------------------
Description:
I'd like to propose adding support for multiple branches and result sets for
Accord transactions. It could look like this:
{code:sql}
BEGIN TRANSACTION
LET a = ...
LET b = ...
IF condition THEN
SELECT 'one', a.value
UPDATE ...
ELSE IF condition2 THEN
SELECT 'two', b.value
UPDATE ...
ELSE
SELECT 'three', NULL
END IF
COMMIT TRANSACTION
{code}
The existing syntax would remain valid, when a single SELECT is defined in
which case the conditional SELECTs would not be valid.
SELECTs would be validated to return columns of the same type. They would be
able to return literals as well.
This would be make the result of the transaction more intuitive as the client
would know explicitly if the updates where applied or not.
The following syntax would be considered as invalid:
1. select defined both on the top level and in branches
{code:sql}
BEGIN TRANSACTION
LET a = ...
LET b = ...
SELECT ...
IF condition THEN
SELECT 'one', a.value
UPDATE ...
ELSE IF condition2 THEN
SELECT 'two', b.value
UPDATE ...
ELSE
SELECT 'three', NULL
END IF
COMMIT TRANSACTION
{code}
2. select defined after update - select must be before the update to make it
clear we select data before modification
{code:sql}
BEGIN TRANSACTION
LET a = ...
LET b = ...
IF condition THEN
UPDATE ...
SELECT 'one', a.value
ELSE IF condition2 THEN
UPDATE ...
SELECT 'two', b.value
ELSE
SELECT 'three', NULL
END IF
COMMIT TRANSACTION
{code}
3. missing select - if select is defined in a single branch, it has to be
defined in all branches:
{code:sql}
BEGIN TRANSACTION
LET a = ...
LET b = ...
IF condition THEN
SELECT 'one', a.value
UPDATE ...
ELSE IF condition2 THEN
SELECT 'two', b.value
UPDATE ...
ELSE
UPDATE ...
END IF
COMMIT TRANSACTION
{code}
{code:sql}
BEGIN TRANSACTION
LET a = ...
LET b = ...
IF condition THEN
SELECT 'one', a.value
UPDATE ...
END IF
COMMIT TRANSACTION
{code}
was:
I'd like to propose adding support for multiple branches and result sets for
Accord transactions. It could look like this:
{code:sql}
BEGIN TRANSACTION
LET a = ...
LET b = ...
IF condition THEN
SELECT 'one', a.value
UPDATE ...
ELSE IF condition2 THEN
SELECT 'two', b.value
UPDATE ...
ELSE
SELECT 'three', NULL
END IF
COMMIT TRANSACTION
{code}
The existing syntax would remain valid, when a single SELECT is defined in
which case the conditional SELECTs would not be valid.
SELECTs would be validated to return columns of the same type. They would be
able to return literals as well.
This would be make the result of the transaction more intuitive as the client
would know explicitly if the updates where applied or not.
> Add support for multiple condition branches and results in Accord transaction
> -----------------------------------------------------------------------------
>
> Key: CASSANDRA-18465
> URL: https://issues.apache.org/jira/browse/CASSANDRA-18465
> Project: Cassandra
> Issue Type: New Feature
> Components: Accord, CQL/Syntax
> Reporter: Jacek Lewandowski
> Priority: Normal
>
> I'd like to propose adding support for multiple branches and result sets for
> Accord transactions. It could look like this:
> {code:sql}
> BEGIN TRANSACTION
> LET a = ...
> LET b = ...
> IF condition THEN
> SELECT 'one', a.value
> UPDATE ...
> ELSE IF condition2 THEN
> SELECT 'two', b.value
> UPDATE ...
> ELSE
> SELECT 'three', NULL
> END IF
> COMMIT TRANSACTION
> {code}
> The existing syntax would remain valid, when a single SELECT is defined in
> which case the conditional SELECTs would not be valid.
> SELECTs would be validated to return columns of the same type. They would be
> able to return literals as well.
> This would be make the result of the transaction more intuitive as the client
> would know explicitly if the updates where applied or not.
> The following syntax would be considered as invalid:
> 1. select defined both on the top level and in branches
> {code:sql}
> BEGIN TRANSACTION
> LET a = ...
> LET b = ...
> SELECT ...
> IF condition THEN
> SELECT 'one', a.value
> UPDATE ...
> ELSE IF condition2 THEN
> SELECT 'two', b.value
> UPDATE ...
> ELSE
> SELECT 'three', NULL
> END IF
> COMMIT TRANSACTION
> {code}
> 2. select defined after update - select must be before the update to make it
> clear we select data before modification
> {code:sql}
> BEGIN TRANSACTION
> LET a = ...
> LET b = ...
> IF condition THEN
> UPDATE ...
> SELECT 'one', a.value
> ELSE IF condition2 THEN
> UPDATE ...
> SELECT 'two', b.value
> ELSE
> SELECT 'three', NULL
> END IF
> COMMIT TRANSACTION
> {code}
> 3. missing select - if select is defined in a single branch, it has to be
> defined in all branches:
> {code:sql}
> BEGIN TRANSACTION
> LET a = ...
> LET b = ...
> IF condition THEN
> SELECT 'one', a.value
> UPDATE ...
> ELSE IF condition2 THEN
> SELECT 'two', b.value
> UPDATE ...
> ELSE
> UPDATE ...
> END IF
> COMMIT TRANSACTION
> {code}
> {code:sql}
> BEGIN TRANSACTION
> LET a = ...
> LET b = ...
> IF condition THEN
> SELECT 'one', a.value
> UPDATE ...
> END IF
> COMMIT TRANSACTION
> {code}
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