[Freeswitch-users] Suggestion to harmonize 'hash' & 'db' insert method

[Ken Rice]

You have to keep in mind that we have to support more then just mysql or
sqlite with the the db interface... This means using SQL that’s common to
ALL platforms include MSSQL, PostgreSQL, Oracle and any other database
someone might want to use via ODBC...

So to do this completely would require modification to the code on insert to
first check if the row exists for the key, then deleting it, then inserting
the new row...  This is going to be the most generic supportable method to
make them work consistently across the board...

However, Keep in mind that what you are calling a bug, could be treated by
many people as a feature... Don’t allow me to create/replace and already
existing key...




On 11/18/12 7:26 AM, "Scott" <8f27e956 at gmail.com> wrote:

> OK, with the one-time CREATE UNIQUE INDEX on 'table'
> (hostname,realm,data_key); stmt in place at the schema-level, a portable
> work-a-like of INSERT OR REPLACE stmt is the UPDATE-INSERT (i.e. "UPSERT" lol)
> stmt pair that follows,
> 
> BEGIN 
> TRANSACTION;                                                                  
>                                               
> UPDATE 'table' SET data_value='value_data' WHERE hostname='value_hostname' AND
> realm='value_realm' AND data_key='value_data_key' ;
> INSERT INTO 'table' (hostname,realm,data_key,data_value) SELECT
> 'value_hostname', 'value_realm', 'value_data_key', 'value_data_value'
>    WHERE NOT EXISTS (SELECT 1 FROM 'table' WHERE hostname='value_hostname' AND
> realm='value_realm' AND data_key='value_data_key' );
> COMMIT;                                                                       
>                                                      
> 
> The two WHERE clauses must be identical and the variables should be in the
> same order as the unique compound index is ordered.
> The UPDATE fails quietly and benignly if the record does NOT already exist and
> succeeds if it does.
> The INSERT ... WHERE NOT EXISTS stmt succeeds if the record does NOT already
> exist fails quietly and benignly if it does.
> The BEGIN and COMMIT aren't typically necessary but they're over-safe just in
> case the same record is attempted by another thread.
> 
> I think this get's it done.
> 
> :-)
> 
> 
> On 18 November 2012 06:25, S. Scott <8f27e956 at gmail.com> wrote:
>> The IF NOT EXITS term is easily omitted.  It's a helper term for batch
>> scripted SQL to prevent an error being thrown in the case of the index
>> already exists as in the case where the make schema script is run more than
>> once.  Easily omitted and, perhaps more properly, replaced with a DROP INDEX
>> stmt and CREATE UNIQUE INDEX stmt pair.
>> 
>> Yeah, i checked further, the OR REPLACE modifier is a little more Hit/miss.
>>  The capability is there typically present, but the syntax varies -- e.g
>> sqlite3 ON REPLACE is mySQL's ON DUPLICATE KEY UPDATE.
>> 
>> Darn shame sqlite3 doesn't support stored procedures 'cause then it's more
>> easily abstracted for portability up the SQL server engine curve.
>> 
>> On 2012-11-18, at 3:53, Gerald Weber <gerald.weber at besharp.at> wrote:
>> 
>>> AFAIK, „if not exists“ and „or replace“ is not ansi sql  syntax, so you will
>>> get in trouble if
>>> someone uses odbc to a db that doesn’t support non standard syntax.
>>>  
>>> The insert or replace could be replaced with the merge statement.
>>>  
>>> Von: freeswitch-users-bounces at lists.freeswitch.org
>>> [mailto:freeswitch-users-bounces at lists.freeswitch.org] Im Auftrag von Scott
>>> Gesendet: Sonntag, 18. November 2012 02:42
>>> An: FreeSWITCH Users Help
>>> Betreff: [Freeswitch-users] Suggestion to harmonize 'hash' & 'db' insert
>>> method
>>>  
>>> Are there reasons why the function 'hash' (non-persistent storage) and
>>> function 'db' (persistent storage) share a look-a-like user interface (e.g.
>>> select/insert/delete) but do not work-a-like.  In particular, in 'hash',
>>> insert overwrites an identical realm/data_key pair whereas 'db' , in so far
>>> as I can tell, just blindly adds, and adds, adds, the insert(s).  However,
>>> the 'db' select method returns one record only even if the db has
>>> accumulated many realm/data_key records, including data_value duplicates. 
>>> 
>>> NOTWITHSTANDING reasons-unknow-to-me, a remedy to harmonize the
>>> non-persistent 'hash' with the persistent 'db'  I *think* is straight
>>> forward ...
>>> 
>>> (1) At the call_limit.db schema-level, a one-time create UNIQUE COMPOUND
>>> index, as follows,
>>> 
>>> CREATE UNIQUE INDEX IF NOT EXISTS 'idx_db_data_HostRealmDK' ON 'db_data'
>>> ('hostname','realm','data_key');
>>> 
>>> (1) At the c-language embedded SQL string-level,
>>> 
>>> change the existing INSERT to be the following,
>>> 
>>> INSERT OR REPLACE INTO db_data (hostname,realm,data_key,data) VALUES
>>> (%s,%s,%s,%s);
>>> 
>>> The index will help speed UP the reads.  Neither change is "exotic" and
>>> should be portable across standard sql implementations.
>>> 
>>> ;-) ... thoughts ?
>>> 
>>> Thanks,
>>> 
>>> 
>>> _________________________________________________________________________
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>>> http://www.freeswitchsolutions.com
>>> 
>>> 
>>> 
>>> 
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> 
> 
> 
> _________________________________________________________________________
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> consulting at freeswitch.org
> http://www.freeswitchsolutions.com
> 
> 
> 
> 
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-- 
Ken
http://www.FreeSWITCH.org
http://www.ClueCon.com
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