The Graph subgraph indexes: Event.logIndex is block-scoped, Event.transactionLogIndex is transaction-scoped — use logIndex for entity ids

Problem: @graphprotocol/graph-ts exposes three similarly named counters — Transaction.index, Event.logIndex, Event.transactionLogIndex — and the Ethereum types are effectively undocumented, so it is easy to build entity ids out of the wrong one.

Semantics: - Transaction.index — position of the transaction within its block. - Event.logIndex — position of the log within the whole **block** (matches the logIndex of eth_getLogs). - Event.transactionLogIndex — position of the log within its **own transaction**, restarting at 0 for each transaction.

Worked example. Block 42 has transactions T0 and T1; T0 emits Foo; T1 emits Foo then Bar.

T0.index = 0                T1.index = 1
T0.Foo:  logIndex 0,  transactionLogIndex 0
T1.Foo:  logIndex 1,  transactionLogIndex 0
T1.Bar:  logIndex 2,  transactionLogIndex 1

Why it matters concretely: the common id recipe is event.transaction.hash.concatI32(event.logIndex.toI32()). Substituting transactionLogIndex there is fine only because the tx hash already scopes it — but a recipe like blockNumber + "-" + transactionLogIndex collides across transactions in the same block, and the subgraph does not error: it overwrites the earlier entity, so events go silently missing. Conversely, if you want to correlate two logs emitted by the same call, transactionLogIndex is the field that gives you ordering within the transaction.

Rule of thumb for deterministic, collision-free ids: transaction hash plus logIndex (or block number plus logIndex, since logIndex is already unique per block). Use transactionLogIndex only for intra-transaction ordering, and note that reorg handling and pruned receipts do not change these definitions.

Source: adapted from a Stack Exchange answer by Paul Razvan Berg (question by Paul Razvan Berg), https://ethereum.stackexchange.com/questions/168867/clarifying-what-the-transactionindex-logindex-and-transactionlogindex-are-in-t — CC BY-SA 4.0