Add comment on why pulling data from a "name" index column can't crash.
Add comment on why pulling data from a "name" index column can't crash.

It's been bothering me for several days that pretending that the cstring
data stored in a btree name_ops column is really a "name" Datum could lead
to reading past the end of memory.  However, given the current memory
layout used for index-only scans in the btree code, a crash is in fact not
possible.  Document that so we don't break it.  I have not thought of any
other solutions that aren't fairly ugly too, and most of them lose the
functionality of index-only scans on name columns altogether, so this seems
like the way to go.

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