PHP tips and tricks: work with IteratorAggregate, Generator, SplQueue and SplDoublyLinkedList.

1. Episode #1.0.2 (2016-05-22) Level: Intermediate
OctoLab Cookbook
How to generate a unique key
for a sequence

2. The context

3. timestamp payment currency
18.03.2016 09:22:23 100 USD
18.03.2016 09:21:02 50 EUR
18.03.2016 09:19:46 10 USD
08.03.2016 09:31:03 10 USD
07.03.2016 22:52:17 145 USD
18.02.2016 23:17:25 35 EUR
Import CSV from tinkoff.ru to TCA application

4. The problem

5. Merging
timestamp payment currency
18.03.2016 09:22:23 100 USD
18.03.2016 09:21:02 50 EUR
18.03.2016 09:19:46 10 USD
timestamp payment currency
18.03.2016 09:19:46 10 USD
08.03.2016 09:31:03 10 USD
07.03.2016 22:52:17 145 USD
18.02.2016 23:17:25 35 EUR
timestamp payment currency
18.02.2016 23:17:25 35 EUR
17.02.2016 19:49:59 11 USD
02.02.2016 17:58:36 9 USD
a first imported CSV file
a second imported CSV file
a third imported CSV file

6. The solution

7. - first iteration: simple, unique key constraint
$table->addUniqueIndex([‘timestamp’,‘payment’,‘currency’]);

8. timestamp payment currency
22.02.2016 20:36:33 15 USD
22.02.2016 19:25:14 25 USD
22.02.2016 00:00:00 0,1 USD
22.02.2016 00:00:00 0,1 USD
21.02.2016 21:19:38 10 USD
21.02.2016 17:04:00 10 USD
valid internal
operations look
exactly the same

9. - second iteration: buffering
and forward hashing
$table->addColumn(‘f_hash’,‘string’, …)
$table->addUniqueIndex([‘f_hash’]);

11. column forward hash
row 1 08bb542ead91978a26317a4aa8caf1e5d355706e
row 2 e993895c5fd4fcbb22f9af9c7d341c47db87a8a7
row 3 7bb25dfeeaec0235cc5cdc4643a09e753687bded
row 4 NULL
buffer size = 2
column forward hash
row 1 bd74be8fda860811368dfc3dd170f34652c73dea
row 2 eaf057a4aac69217b5cc2c996679e7d1e11f411d
row 3 NULL
row 4 NULL
buffer size = 3

12. - third iteration: bidirectional hashing
$table->addColumn(‘b_hash’,‘string’, …)
$table->addUniqueIndex([‘b_hash’]);

14. column forward hash backward hash
row 1 … NULL
row 2 … 0b48e15756c28dc8a00d54594a1c25cabe707973
row 3 … af8d00a06f6e58ec06a650433df597cf4140d78b
row 4 NULL 219fe3369d071daadedf81fde031e0f1e74f571b
buffer size = 2
not-nullable
combination

15. Limitations
• number of rows in a CSV file must be greater
than or equal to the buffer size
Benefits
• import CSV files in any order
• natural flow of the code with minimal changes
in the original iteration

16. • StringifierInterface and CsvRowStringifier
• BufferInterface and HashedBuffer
• BufferedIterator
• changes in the original iteration
The real-world example

17. Thank you for your attention!
Have questions?
Kamil Samigullin
a some developer
kamil@samigullin.info
@ikamilsk
github.com/kamilsk
linkedin.com/in/kamilsk