nizhikov commented on code in PR #13116:
URL: https://github.com/apache/ignite/pull/13116#discussion_r3208600976
##########
docs/_docs/SQL/sql-calcite.adoc:
##########
@@ -483,3 +427,54 @@ Disables certain optimizer rules. This is an optimizer
level hint.
----
SELECT /*+ DISABLE_RULE('MergeJoinConverter') */ T1.* FROM TBL1 T1 JOIN TBL2
T2 ON T1.V1=T2.V1 WHERE T2.V2=?
----
+
+== Transactions [[transactions]]
+
+Transactions on `READ_COMMITTED` isolation level are supported for SQL queries
in Calcite query engine.
+To ensure backward compatibility transactions support disabled, by default.
+To enable, please, configure like the following:
+
+[tabs]
+--
+tab:XML[]
+[source,xml]
+----
+<bean class="org.apache.ignite.configuration.IgniteConfiguration">
+ <property name="transactionConfiguration">
+ <bean class="org.apache.ignite.configuration.TransactionConfiguration">
+ <property name="txAwareQueriesEnabled" value="true" />
+ ...
+ </bean>
+ </property>
+ ...
+</bean>
+----
+--
+
+The following API "transactional aware":
+
+* key-value API.
+* SQL queries with Calcite engine.
+* Scan queries.
+
+"Transactional aware" means:
+
+1. ACID in the same way as key-value API.
+2. Any data changed or removed by the query will not be visible to the
concurrent query until transaction committed.
+3. Any data changed by the query will be returned updated by subsequent
queries of the same transaction.
Review Comment:
Please, see example:
```
try (Transaction tx = ignite.transactions.start()) {
cache.put(1, "test");
var res = sql("SELECT _VAL FROM cache WHERE _KEY = 1");
}
```
If `txAwareQueriesEnabled == false' SELECT will return empty result,
because, transaction not committed.
But, if `txAwareQueriesEnabled == true' SELECT will return "test" row.
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