mysqldump.test calls my_print_defaults in a way that includes the systemwide
my.cnf, so the results will be beyond our control and depend on whatever the
user has in their my.cnf, namely the [mysqldump] section.
call my_print_defaults with --config-file rather than --defaults-extra-file
to prevent inclusion of system-wide defaults and use our config-file only.
(The above problem only occurs with -T -- create a separate file for
each table / view.) This ChangeSet results in correct output of view-
information while omitting the information for the view's stand-in
table. The rationale is that with -T, the user is likely interested
in transferring part of a database, not the db in its entirety (that
would be difficult as replay order is obscure, the files being named
for the table/view they contain rather than getting a sequence number).
'show create' works even on views that are short of a base-table (this
throw a warning though, like you would expect). Unfortunately, this is
not what mysqldump uses; it creates stand-in tables and hence requests
'show fields' on the view which fails with missing base-tables. The
--force option prevents the dump from stopping at this point; furthermore
this patch dumps a comment showing create for the offending view for
better diagnostics. This solution was confirmed by submitter as solving
their/clients' problem. Problem might become non-issue once mysqldump no
longer creates stand-in tables.
mysqldump / SHOW CREATE TABLE will show the NEXT available value for
the PK, rather than the *first* one that was available (that named in
the original CREATE TABLE ... AUTO_INCREMENT = ... statement).
This should produce correct and robust behaviour for the obvious use
cases -- when no data were inserted, then we'll produce a statement
featuring the same value the original CREATE TABLE had; if we dump
with values, INSERTing the values on the target machine should set the
correct next_ID anyway (and if not, we'll still have our AUTO_INCREMENT =
... to do that). Lastly, just the CREATE statement (with no data) for
a table that saw inserts would still result in a table that new values
could safely be inserted to).
There seems to be no robust way however to see whether the next_ID
field is > 1 because it was set to something else with CREATE TABLE
... AUTO_INCREMENT = ..., or because there is an AUTO_INCREMENT column
in the table (but no initial value was set with AUTO_INCREMENT = ...)
and then one or more rows were INSERTed, counting up next_ID. This
means that in both cases, we'll generate an AUTO_INCREMENT =
... clause in SHOW CREATE TABLE / mysqldump. As we also show info on,
say, charsets even if the user did not explicitly give that info in
their own CREATE TABLE, this shouldn't be an issue.
As per above, the next_ID will be affected by any INSERTs that have
taken place, though. This /should/ result in correct and robust
behaviour, but it may look non-intuitive to some users if they CREATE
TABLE ... AUTO_INCREMENT = 1000 and later (after some INSERTs) have
SHOW CREATE TABLE give them a different value (say, CREATE TABLE
... AUTO_INCREMENT = 1006), so the docs should possibly feature a
caveat to that effect.
It's not very intuitive the way it works now (with the fix), but it's
*correct*. We're not storing the original value anyway, if we wanted
that, we'd have to change on-disk representation?
If we do dump/load cycles with empty DBs, nothing will change. This
changeset includes an additional test case that proves that tables
with rows will create the same next_ID for AUTO_INCREMENT = ... across
dump/restore cycles.
Confirmed by support as likely solution for client's problem.
