Comment 1 for bug 1281205

query_history_review table is deprecated in latest version of percona toolkit 2.2.10 (its only available in 2.1)
But still, its true that pt-query-digest reports empty hosts when queries are coming from another server with IP (not hostname)

I run query as a localhost, I'm getting this.

# Query 1: 0.00 QPS, 0.07x concurrency, ID 0x91B86F7C3B10948F at byte 1474
# This item is included in the report because it matches --limit.
# Scores: V/M = 3.84
# Time range: 2014-09-03 14:09:44 to 14:23:27
# Attribute pct total min max avg 95% stddev median
# ============ === ======= ======= ======= ======= ======= ======= =======
# Count 75 3
# Exec time 73 57s 11s 31s 19s 30s 9s 14s
# Lock time 85 984us 223us 384us 328us 366us 71us 366us
# Rows sent 0 0 0 0 0 0 0 0
# Rows examine 79 19.42M 4.00M 10.28M 6.47M 10.25M 2.79M 4.93M
# Rows affecte 65 9.71M 2.00M 5.14M 3.24M 4.93M 1.30M 2.49M
# Bytes sent 93 186 62 62 62 62 0 62
# Query size 87 219 73 73 73 73 0 73
# String:
# Databases test
# Hosts localhost (2/66%), (1/33%)
# Last errno 1592
# Users root
# Query_time distribution

you can see this: # Hosts localhost (2/66%), (1/33%)

If I run with root@192.168.1.37 user, it gives,

# Query 2: 0 QPS, 0x concurrency, ID 0x37C3E49EAECFAC10 at byte 1474 _____
# This item is included in the report because it matches --limit.
# Scores: V/M = 0.00
# Time range: all events occurred at 2014-09-03 14:24:06
# Attribute pct total min max avg 95% stddev median
# ============ === ======= ======= ======= ======= ======= ======= =======
# Count 25 1
# Exec time 26 20s 20s 20s 20s 20s 0 20s
# Lock time 14 161us 161us 161us 161us 161us 0 161us
# Rows sent 0 0 0 0 0 0 0 0
# Rows examine 20 5.14M 5.14M 5.14M 5.14M 5.14M 0 5.14M
# Rows affecte 34 5.14M 5.14M 5.14M 5.14M 5.14M 0 5.14M
# Bytes sent 7 14 14 14 14 14 0 14
# Query size 12 31 31 31 31 31 0 31
# String:
# Databases test
# Hosts
# Last errno 1592
# Users root

You can see that nothing mentioned in Hosts.