updating documentation following recent developments

describing `--concurrent-rowcount`

doc/cheatsheet.md

@@ -37,6 +37,7 @@ gh-ost \
 --allow-master-master \
 --cut-over=default \
 --exact-rowcount \
+--concurrent-rowcount \
 --default-retries=120 \
 --panic-flag-file=/tmp/ghost.panic.flag \
 --postpone-cut-over-flag-file=/tmp/ghost.postpone.flag \
@@ -72,6 +73,7 @@ gh-ost \
 --allow-master-master \
 --cut-over=default \
 --exact-rowcount \
+--concurrent-rowcount \
 --default-retries=120 \
 --panic-flag-file=/tmp/ghost.panic.flag \
 --postpone-cut-over-flag-file=/tmp/ghost.postpone.flag \
@@ -105,6 +107,7 @@ gh-ost \
   --chunk-size=2500 \
   --cut-over=default \
   --exact-rowcount \
+  --concurrent-rowcount \
   --serve-socket-file=/tmp/gh-ost.test.sock \
   --panic-flag-file=/tmp/gh-ost.panic.flag \
   --execute

doc/command-line-flags.md

@@ -32,6 +32,10 @@ user=gromit
 password=123456
   ```
 
+### concurrent-rowcount
+
+See `exact-rowcount`
+
 ### cut-over
 
 Optional. Default is `safe`. See more discussion in [cut-over](cut-over.md)
@@ -44,6 +48,7 @@ A `gh-ost` execution need to copy whatever rows you have in your existing table
 `gh-ost` also supports the `--exact-rowcount` flag. When this flag is given, two things happen:
 - An initial, authoritative `select count(*) from your_table`.
   This query may take a long time to complete, but is performed before we begin the massive operations.
+  When `--concurrent-rowcount` is also specified, this runs in paralell to row copy.
 - A continuous update to the estimate as we make progress applying events.
   We heuristically update the number of rows based on the queries we process from the binlogs.
 

doc/testing-on-replica.md

@@ -54,7 +54,7 @@ $ gh-osc --host=myhost.com --conf=/etc/gh-ost.cnf --database=test --table=sample
 
 Elaborate:
 ```shell
-$ gh-osc --host=myhost.com --conf=/etc/gh-ost.cnf --database=test --table=sample_table --alter="engine=innodb" --chunk-size=2000 --max-load=Threads_connected=20 --switch-to-rbr --initially-drop-ghost-table --initially-drop-old-table --test-on-replica --postpone-cut-over-flag-file=/tmp/ghost-postpone.flag --exact-rowcount --allow-nullable-unique-key --verbose --execute
+$ gh-osc --host=myhost.com --conf=/etc/gh-ost.cnf --database=test --table=sample_table --alter="engine=innodb" --chunk-size=2000 --max-load=Threads_connected=20 --switch-to-rbr --initially-drop-ghost-table --initially-drop-old-table --test-on-replica --postpone-cut-over-flag-file=/tmp/ghost-postpone.flag --exact-rowcount --concurrent-rowcount --allow-nullable-unique-key --verbose --execute
 ```
 - Count exact number of rows (makes ETA estimation very good). This goes at the expense of paying the time for issuing a `SELECT COUNT(*)` on your table. We use this lovingly.
 - Automatically switch to `RBR` if replica is configured as `SBR`. See also: [migrating with SBR](migrating-with-sbr.md)