[BUGS] BUG #14648: counts for queries using array unnesting is incorrect

The following bug has been logged on the website:

Bug reference:      14648
Logged by:          Sebastian Calbaza
Email address:      sebastian.calbaza@hgdata.com
PostgreSQL version: 9.6.2
Operating system:   Ubuntu 14.04 AWS
Description:        

Below is a query that we are using to calculate some counts:   * first version of the query lacks ```unnest(ids) as id,```, but second
one has it  * ```companies``` count value is incorrect for the second one, first
query has the correct value

```
mydb=#           select  count(company) as available,count(distinct
matchedCompany) as matchedCompanies,count(distinct company) as companies
from            (                SELECT  F.urlx as company,
CB_RDPPKLCPQDVACOMSTEFANHGDATACOM_agg.url as matchedCompany                from                 (select unnest(urls) as urlx from
hg_data_discovery_2017_04_10.GroupedFirmographics                    where              (                    (TRUE                     AND TRUE                     AND revenueRangeMin >= 1                     AND employeesRangeMin >= 1                     AND revenueRangeMax <= 1783792664                     AND employeesRangeMax <= 4999000                    )                    OR                     FALSE                  )       ) as I                  inner join (                    select unnest(urls) as urlx from
hg_data_discovery_2017_04_10.GroupedInstallsWithoutDateSignalScore where
productId IN (562) and signalScoreId IN (1,2,3)                    ) as F using(urlx)                left outer join CB_RDPPKLCPQDVACOMSTEFANHGDATACOM_agg on
CB_RDPPKLCPQDVACOMSTEFANHGDATACOM_agg.url=F.urlx where TRUE and TRUE            ) as P                ;available | matchedcompanies | companies 
-----------+------------------+-----------   496493 |            28503 |    495799
(1 row)

Time: 7974.053 ms
mydb=#              select count(id) as people, count(company) as
available,count(distinct matchedCompany) as matchedCompanies,count(distinct
company) as companies from            (                SELECT unnest(ids) as id, F.urlx as company,
CB_RDPPKLCPQDVACOMSTEFANHGDATACOM_agg.url as matchedCompany                from                 (select unnest(urls) as urlx from
hg_data_discovery_2017_04_10.GroupedFirmographics                    where              (                    (TRUE                     AND TRUE                     AND revenueRangeMin >= 1                     AND employeesRangeMin >= 1                     AND revenueRangeMax <= 1783792664                     AND employeesRangeMax <= 4999000                    )                    OR                     FALSE                  )       ) as I                  inner join (                    select unnest(urls) as urlx from
hg_data_discovery_2017_04_10.GroupedInstallsWithoutDateSignalScore where
productId IN (562) and signalScoreId IN (1,2,3)                    ) as F using(urlx)                left outer join CB_RDPPKLCPQDVACOMSTEFANHGDATACOM_agg on
CB_RDPPKLCPQDVACOMSTEFANHGDATACOM_agg.url=F.urlx where TRUE and TRUE            ) as P                ;people | available | matchedcompanies | companies 
--------+-----------+------------------+-----------689905 |    689905 |            28503 |     28503

```




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