Обсуждение: Table count option

<br /><p><font face="Arial">Right clicking on a table show the "count" option, which updates the Rows(counted) value in
theproperties window for the table.</font><p><font face="Arial">Is there an equivalent SQL command? ANALYZE<i>
table_name</i> does not work as the equivalent.</font> 

Melvin Davidson wrote:
> 
> Right clicking on a table show the "count" option, which updates the 
> Rows(counted) value in the properties window for the table.
> 
> Is there an equivalent SQL command? ANALYZE/ table_name/  does not work 
> as the equivalent.
> 

SELECT count(*) FROM table;

Regards Dave

Melvin Davidson wrote:
> Dave,
> 
> Yes  SELECT count(*) FROM table; will give me a count of rows
> but it does _not_ update the "Rows(counted) value in the properties
> window"
> 
> So what is the equivalent function to update the "Rows(counted) value in
> the properties window"???

Right-click -> Count. The value shown is retrieved on the fly using 
SELECT count(*), but only if the estimated value is lower than the 
threshold set under Tools->Options (unless you explicitly select Count 
from the menu).

Regards, Dave

Melvin Davidson wrote:
> OK, one more time.
> 
> Yes I know that right click count does that!
> 
> I know about select count(*).
> I know about Right-click -> Count
> 
> The question was/is "What is the equivalent SQL function to update the
> Rows(counted) value?

Right, one more time :-)

There is no SQL function. It just does a SELECT count(*) and updates the 
value stored in memory (in the pgTable object to be precise).

> IOW, What is the underlying code in Right-click -> Count?

Ultimately, once you get clear of all the menu handling code you get to:

void pgTable::UpdateRows()
{    pgSet *props = ExecuteSet(wxT("SELECT count(*) AS rows FROM ONLY ") 
+ GetQuotedFullIdentifier());    if (props)    {        rows = props->GetLongLong(0);        delete props;
rowsCounted= true;    }
 
}

pgTable.rows contains the row count.
pgTable.rowsCounted is a flag that indicates that a count has been done, 
rather than an estimate made (estimates come from pg_class.reltuples, 
which is populated by ANALYZE).

Regards, Dave