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

[Scott]

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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