745f7bc5f0
* docs: add human readable specifications for stock ledger * docs: reposting technical implementation notes
104 lines
4.1 KiB
Markdown
104 lines
4.1 KiB
Markdown
# Implementation notes for Stock Ledger
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## Important files
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- `stock/stock_ledger.py`
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- `controllers/stock_controller.py`
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- `stock/valuation.py`
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## What is in an Stock Ledger Entry (SLE)?
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Stock Ledger Entry is a single row in the Stock Ledger. It signifies some
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modification of stock for a particular Item in the specified warehouse.
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- `item_code`: item for which ledger entry is made
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- `warehouse`: warehouse where inventory is affected
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- `actual_qty`: change in qty
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- `qty_after_transaction`: quantity available after the transaction is processed
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- `incoming_rate`: rate at which inventory was received.
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- `is_cancelled`: if 1 then stock ledger entry is cancelled and should not be used
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for any business logic except for the code that handles cancellation.
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- `posting_date` & `posting_time`: Specify the temporal ordering of stock ledger
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entries. Ties are broken by `creation` timestamp.
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- `voucher_type`: Many transaction can create SLE, e.g. Stock Entry, Purchase
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Invoice
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- `voucher_no`: `name` of the transaction that created SLE
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- `voucher_detail_no`: `name` of the child table row from parent transaction
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that created the SLE.
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- `dependant_sle_voucher_detail_no`: cross-warehouse transfers need this
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reference in order to update dependent warehouse rates in case of change in
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rate.
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- `recalculate_rate`: if this is checked in/out rates are recomputed on
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transactions.
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- `valuation_rate`: current average valuation rate.
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- `stock_value`: current total stock value
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- `stock_value_difference`: stock value difference made between last and current
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entry. This value is booked in accounting ledger.
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- `stock_queue`: if FIFO/LIFO is used this represents queue/stack maintained for
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computing incoming rate for inventory getting consumed.
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- `batch_no`: batch no for which stock entry is made; each stock entry can only
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affect one batch number.
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- `serial_no`: newline separated list of serial numbers that were added (if
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actual_qty > 0) or else removed. Currently multiple serial nos can have single
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SLE but this will likely change in future.
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## Implementation of Stock Ledger
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Stock Ledger Entry affects stock of combinations of (item_code, warehouse) and
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optionally batch no if specified. For simplicity, lets avoid batch no. for now.
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Stock Ledger Entry table stores stock ledger for all combinations of item_code
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and warehouse. So whenever any operations are to be performed on said
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item-warehouse combination stock ledger is filtered and sorted by posting
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datetime. A typical query that will give you individual ledger looks like this:
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```sql
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select *
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from `tabStock Ledger Entry` as sle
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where
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is_cancelled = 0 --- cancelled entries don't affect ledger
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and item_code = 'item_code' and warehouse = 'warehouse_name'
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order by timestamp(posting_date, posting_time), creation
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```
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New entry is just an update to the last entry which is found by looking at last
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row in the filter ledger.
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### Serial nos
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Serial numbers do not follow any valuation method configuration and they are
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consumed at rate they were produced unless they are grouped in which case they
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are consumed at weighted average rate.
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### Batch Nos
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Batches are currently NOT consumed as per batch wise valuation rate, instead
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global FIFO queue for the item is used for valuation rate.
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## Creation process of SLEs
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- SLE creation is usually triggered by Stock Transactions using a method
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conventionally named `update_stock_ledger()` This might not be defined for
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stock transaction and could be specified somewhere in inheritance hierarchy of
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controllers.
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- This method produces SLE objects which are processed by `make_sl_entries` in
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`stock_ledger.py` which commits the SLE to database.
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- `update_entries_after` class is used to process ONLY the inserted SLE's queue
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and valuation.
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- The change in qty is propagated to future entries immediately. Valuation and
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queue for future entries is processed in background using repost item
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valuation.
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## Accounting impact
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- Accounting impact for stock transaction is handled by `get_gl_entries()`
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method on controllers. Each transaction has different business logic for
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booking the accounting impact.
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