If you are facing following type of error in your sphinx:
FATAL: out of memory (unable to allocate 1073741824 bytes)
then following may be a simple and easy solution for you.
Sphinx FATAL out of memory Error
For an easy solution, just give it a hit and try, and this may be a working solution for you.
Open up your sphinx configuration file, usually named as sphinx.conf, and search for the indexer, which could look like:
mem_limit = 1024M
All you have to do is to chnage the mem_limit value, and reduce it to 128M or 512M, like:
mem_limit = 128M
mem_limit = 512M
Even if the value is not 1024M in your current sphinx configuration, all you have to do is to reduce the value and make it to a lesser memory.
Now restart or reboot your sphinx server completely, and check out if the solution works for you.
Also give your comments out, to let me know if it works.