Inspired by a patch from Julien Rouhaud, but I reworded it.
Discussion: http://postgr.es/m/CAOBaU_a8AH8=ypfqgHnDYu06ts+jWTUgh=VgCxA3yNV-K10j9w@mail.gmail.com
/*
* Hashtable key that defines the identity of a hashtable entry. We separate
* queries by user and by database even if they are otherwise identical.
+ *
+ * Right now, this structure contains no padding. If you add any, make sure
+ * to teach pgss_store() to zero the padding bytes. Otherwise, things will
+ * break, because pgss_hash is created using HASH_BLOBS, and thus tag_hash
+ * is used to hash this.
*/
typedef struct pgssHashKey
{