[Qgis-user] OS Mastermap, SQL Server and QGIS

Fri Jul 12 03:27:21 PDT 2013

Hi Steve,

> As an aside, do you know if the Oracle connector uses the
> user_sdo_geom_metadata table to identify the SRID and extents of the tables?

Not that particular table, not for extents (not sure about SRID). There are
various options for the connector which make things much faster. From the
help:

   - *Only look in meta data table* Restricts the displayed tables to those
   that are in the all_sdo_geom_metadata view. This can speed up the initial
   display of spatial tables.
   - *Use estimated table statistics* for the layer metadata Whenthe layer
   is setup various metadata is required for the Oracle table. Thisincludes
   information such as the table row count, geometry type and spatialextents
   of the data in the geometry column. If the table contains a largenumber of
   rows determining this metadata is time consuming. By activating thisoption
   the following fast table metadata operations are done: Row count
   isdetermined from all_tables.num_rows. Table extents are always determined
   withthe SDO_TUNE.EXTENTS_OF function even if a layer filter is applied. The
   tablegeometry is determined from the first 100 non-null geometry rows in
   the table.

Those two in particular speed things up.

Jonathan

On 11 July 2013 16:19, Steven Campbell <s.campbell at poole.gov.uk> wrote:

> Hi Nathan ****
>
> ** **
>
> Thanks for making the change – it is sooo much quicker now to load,
> especially for such a large dataset as Mastermap!****
>
> ** **
>
> Just a quick question though, if I try to connect to a secondary MSSQL
> database, it takes a very long time to find the tables. Generally what I do
> is I open a boundary file table (stored in one MSSQL table)  so I can zoom
> in to a small location, and then go to open my Mastermap but the initial
> time taken by QGIS to detect the Mastermap table takes a considerable time
> – once found it is quick to open, pan etc – it’s just the initial
> connection that seems very slow.****
>
> ** **
>
> As an aside, do you know if the Oracle connector uses the
> user_sdo_geom_metadata table to identify the SRID and extents of the tables?
> ****
>
> ** **
>
> Thanks again!****
>
> ** **
>
> Steve****
>
> ** **
>
> *From:* Nathan Woodrow [mailto:madmanwoo at gmail.com]
> *Sent:* 02 July 2013 04:02
> *To:* Steven Campbell
> *Cc:* qgis-user
> *Subject:* Re: [Qgis-user] OS Mastermap, SQL Server and QGIS****
>
> ** **
>
> Hey Steven,****
>
> ** **
>
> I have made the change in master now too allow QGIS too look in the
> spatial index table for faster extent loading.  Works like a treat.****
>
> ** **
>
> I would still have the geometry_columns table to allow QGIS to find the
> tables quicker but you don't need the max_x, etc stuff.****
>
> ** **
>
> Thanks for the tip.****
>
> ** **
>
> Regards,****
>
> Nathan****
>
> ** **
>
> On Sat, Jun 29, 2013 at 12:00 AM, Steven Campbell <s.campbell at poole.gov.uk>
> wrote:****
>
> Hi****
>
>  ****
>
> Does anyone else have significant time delays when trying to open large
> datasets from a SQL database in QGIS? I have uploaded my Ordnance survey
> MasterMap data (coverage is the size of an average English County) and
> although the initial connection to identify the table is very quick, the
> loading of the table (even when zoomed in to a very big scale (i.e. 1:100)
> it takes a very long time to open. Once opened the speed is very quick, but
> getting it to open takes a lot of patience as the application appears to
> hang.****
>
>  ****
>
> On a slightly related topic, if I have connected to one MSSQL database,
> QGIS then struggles if I try to connect to an additional database, again it
> just appears to hang for a considerable period of time (30 minutes or more
> at times), it seems odd especially as the connection to the first SQL
> database is almost instant....****
>
>  ****
>
> Any suggestions as to how I can improve this speed would be greatly
> appreciated.****
>
>  ****
>
> Thanks****
>
>  ****
>
> Steve Campbell****
>
> GIS Manager****
>
> Corporate Strategy and Communications****
>
> Borough of Poole | Civic Centre | Poole BH15 2RU****
>
> Tel: 01202 633 362****
>
> Email: s.campbell at poole.gov.uk****
>
> Website:www.boroughofpoole.com****
>
> *Think Green! Please Recycle*****
>
>  ****
>
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