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Update documentation (CORE-4933)

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hvlad 2020-04-20 13:05:48 +03:00
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doc/README.isql_enhancements.txt
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@ -154,3 +154,87 @@ is not accounted for when you type
SET;
in isql to see the state for most options.
Isql enhancements in Firebird v3.
---------------------------------
9) SET KEEP_TRAN_PARAMS option.
Author: Vladyslav Khorsun <hvlad at users sourcefoege net>
When set to ON, isql keeps text of following successful SET TRANSACTION statement and
new DML transactions is started using the same SQL text (instead of defaul CONCURRENCY
WAIT mode).
When set to OFF, isql start new DML transaction as usual.
Name KEEP_TRAN_PARAMS could be cut down to the KEEP_TRAN.
In Firebird 3 KEEP_TRAN_PARAMS value is OFF by default, preserving backward compatibility
with old behaviour.
In Firebird 4 KEEP_TRAN_PARAMS is ON by default to make isql behaviour more logical.
Example:
-- check current value
SQL> SET;
...
Keep transaction params: OFF
-- toggle value
SQL> SET KEEP_TRAN;
SQL> SET;
...
Keep transaction params: ON
SET TRANSACTION
SQL>commit;
-- start new transaction, check KEEP_TRAN value and actual transaction's
-- parameters
SQL>SET TRANSACTION READ COMMITTED WAIT;
SQL>SET;
...
Keep transaction params: ON
SET TRANSACTION READ COMMITTED WAIT
SQL> SELECT RDB$GET_CONTEXT('SYSTEM', 'ISOLATION_LEVEL') FROM RDB$DATABASE;
RDB$GET_CONTEXT
=============================================================
READ COMMITTED
SQL> commit;
-- start new transaction, ensure is have parameters as KEEP_TRAN value
SQL> SELECT RDB$GET_CONTEXT('SYSTEM', 'ISOLATION_LEVEL') FROM RDB$DATABASE;
RDB$GET_CONTEXT
=============================================================
READ COMMITTED
-- disable KEEP_TRAN, current transaction is not changed
SQL> SET KEEP_TRAN OFF;
SQL> SELECT RDB$GET_CONTEXT('SYSTEM', 'ISOLATION_LEVEL') FROM RDB$DATABASE;
RDB$GET_CONTEXT
=============================================================
READ COMMITTED
SQL> commit;
-- start new transaction, ensure is have default parameters (SNAPSHOT)
SQL> SELECT RDB$GET_CONTEXT('SYSTEM', 'ISOLATION_LEVEL') FROM RDB$DATABASE;
RDB$GET_CONTEXT
=============================================================
SNAPSHOT
SQL> SET;
...
Keep transaction params: OFF
SQL>