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rowland / fb

Firebird Extension Library for Ruby
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Why any select in WRITE transactions? #54

Closed woblavobla closed 6 years ago

woblavobla commented 7 years ago

After every select commit transaction is called. Why is that? And how to turn this feature off?

`Statement 395766:

SELECT * FROM PROJECTS ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PLAN (PROJECTS NATURAL)

2017-03-02T16:55:15.2890 (2124:00000000015FA0B8) COMMIT_TRANSACTION E:\WORK\TRUNKDB\RED2MINE.FDB (ATT_46229, SYSDBA:NONE, UTF8, TCPv4:127.0.0.1) C:\Ruby23\bin\ruby.exe:4124 (TRA_304960647, CONCURRENCY | WAIT | READ_WRITE) 0 ms, 1 read(s), 1 write(s), 1 fetch(es), 1 mark(s)

2017-03-02T16:55:37.1870 (2124:00000000015FA0B8) START_TRANSACTION E:\WORK\TRUNKDB\RED2MINE.FDB (ATT_46229, SYSDBA:NONE, UTF8, TCPv4:127.0.0.1) C:\Ruby23\bin\ruby.exe:4124 (TRA_304960648, CONCURRENCY | WAIT | READ_WRITE)

2017-03-02T16:55:37.1920 (2124:00000000015FA0B8) PREPARE_STATEMENT E:\WORK\TRUNKDB\RED2MINE.FDB (ATT_46229, SYSDBA:NONE, UTF8, TCPv4:127.0.0.1) C:\Ruby23\bin\ruby.exe:4124 (TRA_304960648, CONCURRENCY | WAIT | READ_WRITE) `

rowland commented 7 years ago

Every statement Firebird executes must be within the scope of a transaction. If, using fb, you execute a statement without first starting a transaction, a transaction is implicitly started and automatically committed.

The README contains examples of explicit transaction usage.

woblavobla commented 7 years ago

@rowland Okay, i got it. But in what direction should i look, to change default behavior to start Transaction with select in READ_ONLY?

rowland commented 7 years ago

I think you want to just do conn.transaction('READ ONLY'), not forgetting to commit eventually. Making all implicitly-started transactions read only would break things.

woblavobla commented 7 years ago

@rowland i want to make all implicitly-started select transactions read only. Because if db have forced_write flag true, it will perform writes to db on each select.

rowland commented 7 years ago

It might be possible, but it would take redesigning the library. Feel free to fork it. Might be easier to just start read-only transactions though.

On Mar 5, 2017, at 12:22, Andrey Lobanov notifications@github.com wrote:

@rowland i want to make all implicitly-started select transactions read only. Because if db have forced_write flag true, it will perform writes to db on each select.

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

woblavobla commented 7 years ago

@rowland As i can see we can't determine type of statement before it is prepared. But to prepare statement we should start transaction. Any ideas?

rowland commented 7 years ago

I really don't know what problem you're trying to solve.

On Thu, Mar 9, 2017 at 4:35 AM, Andrey Lobanov notifications@github.com wrote:

@rowland https://github.com/rowland As i can see we can't determine type of statement before it is prepared. But to prepare statement we should start transaction. Any ideas?

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/rowland/fb/issues/54#issuecomment-285339877, or mute the thread https://github.com/notifications/unsubscribe-auth/AAAWwILAKsXoMTKdfkCg0ULXTSKONxZ5ks5rj_IngaJpZM4MRBZ4 .

-- Brent Rowland

woblavobla commented 7 years ago

@rowland The main idea is to all implicitly started transactions(with select statements) made read only.