Fix a small memory leak in ExecReScanAgg() in the hashed aggregation case. In the previous coding, the list of columns that needed to be hashed on was allocated in the per-query context, but we reallocated every time the Agg node was rescanned. Since this information doesn't change over a rescan, just construct the list of columns once during ExecInitAgg().
Fix a small memory leak in ExecReScanAgg() in the hashed aggregation case.
In the previous coding, the list of columns that needed to be hashed on
was allocated in the per-query context, but we reallocated every time
the Agg node was rescanned. Since this information doesn't change over
a rescan, just construct the list of columns once during ExecInitAgg().

lisakowen/gpdb,Chibin/gpdb,Postgres-XL/Postgres-XL,arcivanov/postgres-xl,lisakowen/gpdb,Chibin/gpdb,pavanvd/postgres-xl,Postgres-XL/Postgres-XL,greenplum-db/gpdb,zeroae/postgres-xl,yuanzhao/gpdb,adam8157/gpdb,postmind-net/postgres-xl,Postgres-XL/Postgres-XL,lisakowen/gpdb,adam8157/gpdb,yuanzhao/gpdb,50wu/gpdb,jmcatamney/gpdb,adam8157/gpdb,oberstet/postgres-xl,lisakowen/gpdb,greenplum-db/gpdb,postmind-net/postgres-xl,yazun/postgres-xl,lisakowen/gpdb,tpostgres-projects/tPostgres,arcivanov/postgres-xl,pavanvd/postgres-xl,ashwinstar/gpdb,techdragon/Postgres-XL,snaga/postgres-xl,postmind-net/postgres-xl,zeroae/postgres-xl,yuanzhao/gpdb,adam8157/gpdb,ashwinstar/gpdb,tpostgres-projects/tPostgres,Postgres-XL/Postgres-XL,yuanzhao/gpdb,greenplum-db/gpdb,50wu/gpdb,yuanzhao/gpdb,oberstet/postgres-xl,xinzweb/gpdb,Chibin/gpdb,postmind-net/postgres-xl,ovr/postgres-xl,arcivanov/postgres-xl,tpostgres-projects/tPostgres,arcivanov/postgres-xl,yazun/postgres-xl,edespino/gpdb,Chibin/gpdb,edespino/gpdb,kmjungersen/PostgresXL,snaga/postgres-xl,yuanzhao/gpdb,edespino/gpdb,Chibin/gpdb,pavanvd/postgres-xl,kmjungersen/PostgresXL,pavanvd/postgres-xl,Chibin/gpdb,oberstet/postgres-xl,ovr/postgres-xl,jmcatamney/gpdb,oberstet/postgres-xl,xinzweb/gpdb,Chibin/gpdb,ovr/postgres-xl,postmind-net/postgres-xl,Postgres-XL/Postgres-XL,xinzweb/gpdb,techdragon/Postgres-XL,arcivanov/postgres-xl,Chibin/gpdb,techdragon/Postgres-XL,edespino/gpdb,snaga/postgres-xl,greenplum-db/gpdb,yazun/postgres-xl,zeroae/postgres-xl,ashwinstar/gpdb,edespino/gpdb,lisakowen/gpdb,yuanzhao/gpdb,adam8157/gpdb,ashwinstar/gpdb,kmjungersen/PostgresXL,tpostgres-projects/tPostgres,greenplum-db/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,kmjungersen/PostgresXL,snaga/postgres-xl,jmcatamney/gpdb,xinzweb/gpdb,edespino/gpdb,ovr/postgres-xl,adam8157/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,yuanzhao/gpdb,greenplum-db/gpdb,50wu/gpdb,50wu/gpdb,zeroae/postgres-xl,ovr/postgres-xl,jmcatamney/gpdb,yazun/postgres-xl,jmcatamney/gpdb,50wu/gpdb,jmcatamney/gpdb,50wu/gpdb,adam8157/gpdb,lisakowen/gpdb,techdragon/Postgres-XL,edespino/gpdb,ashwinstar/gpdb,zeroae/postgres-xl,50wu/gpdb,Chibin/gpdb,yuanzhao/gpdb,pavanvd/postgres-xl,lisakowen/gpdb,xinzweb/gpdb,edespino/gpdb,xinzweb/gpdb,edespino/gpdb,edespino/gpdb,arcivanov/postgres-xl,Chibin/gpdb,yuanzhao/gpdb,xinzweb/gpdb,yazun/postgres-xl,jmcatamney/gpdb,techdragon/Postgres-XL,tpostgres-projects/tPostgres,greenplum-db/gpdb,adam8157/gpdb,xinzweb/gpdb,snaga/postgres-xl,50wu/gpdb,ashwinstar/gpdb,kmjungersen/PostgresXL