[Qgis-developer] oracle performances

[Jürgen E. Fischer]

Hi Giovanni,

On Tue, 26. Feb 2013 at 17:54:13 +0000, Giovanni Manghi wrote:
> > Are you using integer primary keys?
 
> right now I have difficulties accessing the VPN but at least they gave
> me the structure of one of the tables I tested

> CREATE TABLE "QGIS_TEST"."SEDI_ELETTORALI" ( "OBJECTID" NUMBER(38,0) NOT NULL ENABLE, "NOME_SEDE" VARCHAR2(50 BYTE), "INDIRIZZO" VARCHAR2(100 BYTE), "QUARTIERE" VARCHAR2(10 BYTE), "EDIFICIO" VARCHAR2(10 BYTE), "SEZIONI" VARCHAR2(100 BYTE), "IDJOBSTAT" NUMBER(10,0), "SE_ANNO_CAD_DATA" BLOB, "SHAPE" "MDSYS"."SDO_GEOMETRY" ) PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT) TABLESPACE "QGIS_TEST" LOB ("SE_ANNO_CAD_DATA") STORE AS ( TABLESPACE "QGIS_TEST" ENABLE STORAGE IN ROW CHUNK 8192 PCTVERSION 10 NOCACHE LOGGING STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT)) ;

AFAICT that doesn't mention a primary key.  QGIS might resort to using the
ROWID as primary key (check the medadata tab in vector layer properties), which
is mapped to a integer using a QHash, which is quite expensive.

BTW you can also use Oracle Express Edition to test the provider[1] - no need
for tunnels...


Jürgen 

[1] http://www.oracle.com/technetwork/products/express-edition/downloads/index.html

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