feat: allow get_notes to return zero notes

[nventuro]

get_notes used to fail if no notes were found ever since #4988 was merged. The argument there was that since no constraints are applied, and note non-existence cannot be proved, get_notes returning no notes is always a mistake.

However, what that mistake means depends on the caller. Since we don't want for the caller to have to pass an error message to get_notes, I think it's better to return no notes and leave it up to the caller to decide what to do. BoundedVec is a safe container: get will result in errors if used with indices out of bounds.

I changed the callsites where we did get_unchecked(0) to get(0) - this means that the errors now change from 'got 0 notes' to 'out of bounds access'. Neither error message is great, so I didn't bother improving this. Maybe we could have a get variant that received an error message (like Option::expect), but we don't need to worry about this for now.

Closes #7059
(indirectly due to how we need to change certain tests to address this)

[sklppy88]

lgtm

[AztecBot]

Benchmark results

Metrics with a significant change:

• avm_simulation_time_ms (Token:transfer_public): 28.7 (-36%)
• protocol_circuit_proving_time_in_ms (base-parity): 1,384 (-30%)

Detailed results

All benchmarks are run on txs on the Benchmarking contract on the repository. Each tx consists of a batch call to create_note and increment_balance, which guarantees that each tx has a private call, a nested private call, a public call, and a nested public call, as well as an emitted private note, an unencrypted log, and public storage read and write.

This benchmark source data is available in JSON format on S3 here.

Proof generation

Each column represents the number of threads used in proof generation.

Metric	1 threads	4 threads	16 threads	32 threads	64 threads
proof_construction_time_sha256_ms	5,758 (-1%)	1,557 (-1%)	726 (+3%)	769 (+2%)	805 (+3%)
proof_construction_time_sha256_30_ms	11,818 (-1%)	3,182	1,460 (+3%)	1,488 (+3%)	1,523 (+4%)
proof_construction_time_sha256_100_ms	44,143	12,090 (+1%)	5,680 (+4%)	5,628 (+3%)	5,622 (+4%)
proof_construction_time_poseidon_hash_ms	78.0 (-1%)	35.0 (+3%)	36.0 (+6%)	62.0 (+7%)	91.0 (+3%)
proof_construction_time_poseidon_hash_30_ms	1,531	420 (-1%)	211 (+4%)	232 (+4%)	280 (+3%)
proof_construction_time_poseidon_hash_100_ms	5,645 (-1%)	1,522	707 (+4%)	753 (+4%)	782 (+4%)

L2 block published to L1

Each column represents the number of txs on an L2 block published to L1.

Metric	4 txs	8 txs	16 txs
l1_rollup_calldata_size_in_bytes	708	708	708
l1_rollup_calldata_gas	6,600	6,576	6,600
l1_rollup_execution_gas	584,280	584,407	584,582
l2_block_processing_time_in_ms	760 (-2%)	1,444 (+2%)	2,706 (-3%)
l2_block_building_time_in_ms	10,839	21,034 (-1%)	41,572 (-1%)
l2_block_rollup_simulation_time_in_ms	10,839	21,033 (-1%)	41,572 (-1%)
l2_block_public_tx_process_time_in_ms	9,066	19,064 (-1%)	39,528 (-1%)

L2 chain processing

Each column represents the number of blocks on the L2 chain where each block has 8 txs.

Metric	3 blocks	5 blocks
node_history_sync_time_in_ms	7,140 (+2%)	10,192 (+4%)
node_database_size_in_bytes	12,722,256	16,937,040
pxe_database_size_in_bytes	16,254	26,813

Circuits stats

Stats on running time and I/O sizes collected for every kernel circuit run across all benchmarks.

Circuit	simulation_time_in_ms	witness_generation_time_in_ms	input_size_in_bytes	output_size_in_bytes	proving_time_in_ms	proof_size_in_bytes	num_public_inputs	size_in_gates
private-kernel-init	104 (-1%)	412 (+2%)	21,845	53,090	N/A	N/A	N/A	N/A
private-kernel-inner	188 (+1%)	721 (+2%)	81,005	53,266	N/A	N/A	N/A	N/A
private-kernel-tail	450	896 (+3%)	61,240	57,447	N/A	N/A	N/A	N/A
base-parity	6.46 (+1%)	683 (-1%)	160	96.0	⚠️ 1,384 (-30%)	13,188	19.0	131,072
root-parity	112	132 (+6%)	69,084	96.0	31,461	13,188	19.0	4,194,304
base-rollup	3,396 (-1%)	5,013	182,192	632	45,259 (+1%)	13,988	44.0	4,194,304
root-rollup	155	121 (-2%)	54,429	652	28,942	13,924	42.0	4,194,304
public-kernel-setup	117 (+1%)	2,748 (+4%)	112,985	80,246	18,011 (+1%)	141,444	4,027	2,097,152
public-kernel-app-logic	120 (-2%)	4,141 (+2%)	112,985	80,246	11,071 (-2%)	141,444	4,027	1,048,576
public-kernel-tail	635 (-1%)	27,820 (-2%)	410,726	10,814	69,557 (+1%)	26,372	431	8,388,608
private-kernel-reset-tiny	232	893 (+2%)	76,596	52,961	N/A	N/A	N/A	N/A
private-kernel-tail-to-public	5,252 (+1%)	1,669 (+5%)	900,419	1,697	N/A	N/A	N/A	N/A
public-kernel-teardown	102	4,066	112,985	80,246	19,529 (-1%)	141,444	4,027	2,097,152
merge-rollup	61.7 (+1%)	N/A	35,678	632	N/A	N/A	N/A	N/A
undefined	N/A	N/A	N/A	N/A	158,436 (+2%)	N/A	N/A	N/A

Stats on running time collected for app circuits

Function	input_size_in_bytes	output_size_in_bytes	witness_generation_time_in_ms	proof_size_in_bytes	proving_time_in_ms
ContractClassRegisterer:register	1,312	11,699	343 (-1%)	N/A	N/A
ContractInstanceDeployer:deploy	1,376	11,699	27.5	N/A	N/A
MultiCallEntrypoint:entrypoint	1,888	11,699	607	N/A	N/A
GasToken:deploy	1,344	11,699	440 (+2%)	N/A	N/A
SchnorrAccount:constructor	1,280	11,699	430	N/A	N/A
SchnorrAccount:entrypoint	2,272	11,699	821	N/A	N/A
Token:privately_mint_private_note	1,248	11,699	510	N/A	N/A
FPC:fee_entrypoint_public	1,312	11,699	90.9 (+2%)	N/A	N/A
Token:transfer	1,280	11,699	1,324	N/A	N/A
AuthRegistry:set_authorized (avm)	21,702	N/A	N/A	102,048	2,128 (+2%)
FPC:prepare_fee (avm)	25,150	N/A	N/A	102,112	2,191 (+3%)
Token:transfer_public (avm)	58,188	N/A	N/A	102,112	6,805 (+3%)
AuthRegistry:consume (avm)	35,580	N/A	N/A	102,080	2,588 (+2%)
FPC:pay_refund (avm)	30,010	N/A	N/A	102,080	3,506 (-2%)
Benchmarking:create_note	1,312	11,699	421	N/A	N/A
SchnorrAccount:verify_private_authwit	1,248	11,699	44.4 (+1%)	N/A	N/A
Token:unshield	1,344	11,699	1,144	N/A	N/A
FPC:fee_entrypoint_private	1,344	11,699	1,417	N/A	N/A

AVM Simulation

Time to simulate various public functions in the AVM.

Function	time_ms	bytecode_size_in_bytes
GasToken:_increase_public_balance	102 (+2%)	13,790
GasToken:set_portal	15.6 (+7%)	3,339
Token:constructor	124	23,692
FPC:constructor	95.3 (+1%)	13,592
GasToken:mint_public	82.1 (-2%)	10,158
Token:mint_public	61.9 (-14%)	19,034
Token:assert_minter_and_mint	71.8 (+16%)	12,925
AuthRegistry:set_authorized	47.7 (-2%)	7,812
FPC:prepare_fee	238 (-7%)	11,068
Token:transfer_public	⚠️ 28.7 (-36%)	44,012
FPC:pay_refund	85.1 (+17%)	15,961
Benchmarking:increment_balance	1,057	11,281
Token:_increase_public_balance	15.2 (+2%)	15,006
FPC:pay_refund_with_shielded_rebate	135 (+2%)	17,056

Public DB Access

Time to access various public DBs.

Function	time_ms
get-nullifier-index	0.153 (-7%)

Tree insertion stats

The duration to insert a fixed batch of leaves into each tree type.

Metric	1 leaves	16 leaves	64 leaves	128 leaves	256 leaves	512 leaves	1024 leaves
batch_insert_into_append_only_tree_16_depth_ms	10.3 (-1%)	16.8 (+1%)	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_16_depth_hash_count	16.8	31.7	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_16_depth_hash_ms	0.598	0.517 (+1%)	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_32_depth_ms	N/A	N/A	47.9	75.9 (-3%)	131 (-1%)	248 (+1%)	467 (-1%)
batch_insert_into_append_only_tree_32_depth_hash_count	N/A	N/A	95.9	159	287	543	1,055
batch_insert_into_append_only_tree_32_depth_hash_ms	N/A	N/A	0.490	0.466 (-2%)	0.449 (-1%)	0.448 (+1%)	0.436 (-1%)
batch_insert_into_indexed_tree_20_depth_ms	N/A	N/A	59.4	111 (-1%)	184	357 (+1%)	689 (-1%)
batch_insert_into_indexed_tree_20_depth_hash_count	N/A	N/A	109	207	355	691	1,363
batch_insert_into_indexed_tree_20_depth_hash_ms	N/A	N/A	0.502	0.499	0.486	0.483 (+1%)	0.474 (-1%)
batch_insert_into_indexed_tree_40_depth_ms	N/A	N/A	73.4	N/A	N/A	N/A	N/A
batch_insert_into_indexed_tree_40_depth_hash_count	N/A	N/A	133	N/A	N/A	N/A	N/A
batch_insert_into_indexed_tree_40_depth_hash_ms	N/A	N/A	0.521	N/A	N/A	N/A	N/A

Miscellaneous

Transaction sizes based on how many contract classes are registered in the tx.

Metric	0 registered classes	1 registered classes
tx_size_in_bytes	72,017	666,910

Transaction size based on fee payment method

| Metric | |
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[nventuro]

Some of the tests were slightly trickier to fix: in doing so I also closed #7059.