ZINC.D128

Increments a 128-bit decimal value in the ZMap ordered key-value store.

Syntax

ZINC.D128 <key> <value>

Parameters

Parameter	Type	Required	Description
key	bytes	Yes	The key to increment.
value	string	Yes	A decimal number to add to the current value. Accepts plain decimals and scientific notation (e.g., 1.5E+10). Use a negative number to decrement.

Return Value

Simple string: OK on success.

Behavior

ZINC.D128 performs a high-precision decimal increment on a key in the ZMap subspace of the session’s current namespace. It uses IEEE-754 decimal128 (BID encoding), which provides 34 significant digits and an exponent range of ±6144, far exceeding the ~15 significant digits of ZINC.F64.

Like ZINC.F64, this command performs a read-modify-write cycle because FoundationDB has no atomic decimal128-add mutation. This means concurrent ZINC.D128 calls on the same key can cause transaction conflicts.

If the key does not exist, it is created with an implicit starting value of zero and then incremented by value.

The value is encoded as 16 bytes in little-endian IEEE-754 BID format (low 8 bytes first, high 8 bytes second). Three validation guards protect against invalid states:

1. Valid input: the delta must be a parseable decimal string; unparseable strings are rejected.
2. Valid stored size: if the key already exists, the stored value must be exactly 16 bytes.
3. Range check: the computed result must be representable as a Decimal128; values that exceed the Decimal128 range are rejected.

The command supports two transaction modes:

• Auto-commit (one-off): When no explicit transaction is active, Kronotop creates a transaction, performs the operation, and commits it immediately. This is the default mode.
• Explicit transaction: When a BEGIN has been issued, the operation is staged in the current transaction and only persists when COMMIT is called.

ZINC.D128 is a write operation and does not support snapshot reads.

All data is scoped to the session’s active namespace. The same key in different namespaces refers to different entries.

Errors

Error Code	Description
ERR invalid decimal	The provided value is not a valid decimal number.
ERR Invalid stored value: expected 16-byte Decimal128 (IEEE-754 BID)	The existing value at the key is not 16 bytes.
ERR Exponent is out of range for Decimal128 encoding ...	The result exceeds the Decimal128 representable range.
ERR	Wrong number of arguments or internal failure.

Examples

Increment a new key (implicit zero start):

> ZINC.D128 counter 10.5
OK

> ZGET.D128 counter
"10.5"

Accumulate multiple increments:

> ZINC.D128 counter 1.5
OK

> ZINC.D128 counter 3.0
OK

> ZINC.D128 counter 4.5
OK

> ZGET.D128 counter
"9.0"

Decrement with a negative value:

> ZINC.D128 counter 100.0
OK

> ZINC.D128 counter -30.5
OK

> ZGET.D128 counter
"69.5"

High-precision decimal (34 significant digits):

> ZINC.D128 counter 0.123456789012345678901234567890123
OK

> ZGET.D128 counter
"0.123456789012345678901234567890123"

Use within an explicit transaction:

> BEGIN
OK

> ZINC.D128 tx-counter 42.42
OK

> COMMIT
OK

> ZGET.D128 tx-counter
"42.42"