ChangeHandler

ChangeHandler creates SQL statements for changing rows in a table.

Summary

ChangeHandler	ChangeHandler creates SQL statements for changing rows in a table.
Variables
$DUPE_KEY
@ACTIONS
Functions
new
fetch_back	Set the fetch-back dbh.
set_src	Set which side of left-right pair is the source.
src	Return current source db.tbl (could be left or right table).
dst	Return current destination db.tbl (could be left or right table).
_take_action	Call the user-provied actions.
change	Make an action SQL statment for the given parameters if not queueing.
__queue	Queue an action for later execution.
process_rows	Make changes to rows created/queued earlier.
make_DELETE	Make a DELETE statement.
make_UPDATE	Make an UPDATE statement.
make_INSERT	Make an INSERT statement.
make_REPLACE	Make a REPLACE statement.
make_row	Make an INSERT or REPLACE statement.
make_where_clause	Make a WHERE clause.
get_changes	Get a summary of changes made.
sort_cols	Sort a row’s columns based on their real order in the table.
make_fetch_back_query	Make a SELECT statement to fetch-back values.
_d

Variables

$DUPE_KEY

my $DUPE_KEY

@ACTIONS

our @ACTIONS

Functions

new

sub new

Parameters

%args

Arguments

Required Arguments

left_db	Left database (src by default)
left_tbl	Left table (src by default)
right_db	Right database (dst by default)
right_tbl	Right table (dst by default)
actions	arrayref of subroutines to call when handling a change.
replace	Do UPDATE/INSERT as REPLACE.
queue	Queue changes until process_rows() is called with a greater queue level.
Quoter	Quoter object

Optional Arguments

tbl_struct	Used to sort columns and detect binary columns
hex_blob	HEX() BLOB columns (default yes)

Returns

ChangeHandler object

fetch_back

sub fetch_back

Set the fetch-back dbh. If I’m supposed to fetch-back, that means I have to get the full row from the database. For example, someone might call me like so: $me->change(‘UPDATE’, { a => 1 }) But ‘a’ is only the primary key. I now need to select that row and make an UPDATE statement with all of its columns.

Parameters

$dbh	dbh to use for fetching-back values

set_src

sub set_src

Set which side of left-right pair is the source. For bidirectional syncing both tables are src and dst. Internally, we refer to the tables generically as the left and right. Either one can be src or dst, as set by this sub when called by the caller. Other subs don’t know to which table src or dst point. They just fetchback from src and change dst. If the optional $dbh arg is given, fetch_back() is set with it, too.

Parameters

$src	Hashref with source host information
$dbh	Set fetch_back() with this dbh if given

src

sub src

Return current source db.tbl (could be left or right table).

Returns

Source database-qualified table name

dst

sub dst

Return current destination db.tbl (could be left or right table).

Returns

Destination database-qualified table name

_take_action

sub _take_action

Call the user-provied actions. Actions are passed an action statement and an optional dbh. This sub is not called directly; it’s called by change() or process_rows().

Parameters

sql	A SQL statement
dbh	optional dbh passed to the action callback

change

sub change

Make an action SQL statment for the given parameters if not queueing. This sub calls _take_action(), passing the action statement and optional dbh. If queueing, the parameters are saved and the same work is done in process_rows(). Queueing does not work with bidirectional syncs.

Parameters

action	One of @ACTIONS
row	Hashref of row data
cols	Arrayref of column names
dbh	Optional dbh passed to _take_action()

__queue

sub __queue

Queue an action for later execution. This sub is called by change() process_rows() to defer action.

Parameters

action	One of @ACTIONS
row	Hashref of row data
cols	Arrayref of column names
dbh	Optional dbh passed to _take_action()

process_rows

sub process_rows

Make changes to rows created/queued earlier. If called with 1, will process rows that have been deferred from instant processing. If no arg, will process all rows.

Parameters

$queue_level	Queue level caller is in
$trace_msg	Optional string to append to each SQL statement for tracing them in binary logs.

make_DELETE

sub make_DELETE

Make a DELETE statement. DELETE never needs to be fetched back.

Parameters

$row	Hashref with row values
$cols	Arrayref with column names

Returns

A DELETE statement for the given row and columns

make_UPDATE

sub make_UPDATE

Make an UPDATE statement.

Parameters

$row	Hashref with row values
$cols	Arrayref with column names

Returns

An UPDATE statement for the given row and columns

make_INSERT

sub make_INSERT

Make an INSERT statement. This sub is stub for make_row() which does the real work.

Parameters

$row	Hashref with row values
$cols	Arrayref with column names

Returns

An INSERT statement for the given row and columns

make_REPLACE

sub make_REPLACE

Make a REPLACE statement. This sub is a stub for make_row() which does the real work.

Parameters

$row	Hashref with row values
$cols	Arrayref with column names

Returns

A REPLACE statement for the given row and columns

make_row

sub make_row

Make an INSERT or REPLACE statement. Values from $row are quoted with Quoter::quote_val().

Parameters

$verb	”INSERT” or “REPLACE”
$row	Hashref with row values
$cols	Arrayref with column names

Returns

A SQL statement

make_where_clause

sub make_where_clause

Make a WHERE clause. Values are quoted with Quoter::quote_val().

Parameters

$row	Hashref with row values
$cols	Arrayref with column names

Returns

A WHERE clause without the word “WHERE”

get_changes

sub get_changes

Get a summary of changes made.

Returns

Hash of changes where the keys are actions like “DELETE” and the values are how many of the action were made

sort_cols

sub sort_cols

Sort a row’s columns based on their real order in the table. This requires that the optional tbl_struct arg was passed to new(). If not, the rows are sorted alphabetically.

Parameters

$row	Hashref with row values

Returns

Array of column names

make_fetch_back_query

sub make_fetch_back_query

Make a SELECT statement to fetch-back values. This requires that the optional tbl_struct arg was passed to new().

Parameters

$where

Optional WHERE clause without the word “WHERE”

Returns

A SELECT statement

_d

sub _d