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Select Filter

The Select filter keeps only the events that match a predicate and drops the rest — so a sink downstream sees just the transactions you care about (by address, asset, datum, or metadata). It’s the workhorse for “tell me when X happens on chain”.

Select works on structured records, so it needs the ParseCbor filter earlier in the chain (usually preceded by SplitBlock for tx-level matching).

Configuration

daemon.toml
[[filters]]
type = "Select"
skip_uncertain = true
predicate = <match>
  • type (required): the literal value Select.
  • skip_uncertain (required): when true, events that can’t be conclusively evaluated against the predicate are dropped rather than kept.
  • predicate (required): the match expression — see the patterns below.

Simple predicates

The simplest predicate is a single string that matches any transaction touching a given entity.

Match a transaction that interacts with an address:

predicate = "addr1qx2fxv2umyhttkxyxp8x0dlpdt3k6cwng5pxj3jhsydzer3n0d3vllmyqwsx5wktcd8cc3sq835lu7drv2xwl2wywfgse35a3x"

Match a stake address:

predicate = "stake178phkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gtcccycj5"

Match an asset:

predicate = "asset17jd78wukhtrnmjh3fngzasxm8rck0l2r4hhyyt"

Match a datum:

predicate = "datum1httkxyxp8x0dlpdt3k6cwng5pxj3j"

Match a metadata label (prefix the label with #):

predicate = "#127"

Combining predicates

Use any (match if any entry matches) or all (match only if every entry matches) to compose simple predicates.

Match a transaction touching any of these addresses:

[filters.predicate]
any = [
    "addr1qx2fxv2umyhttkxyxp8x0dlpdt3k6cwng5pxj3jhsydzer3n0d3vllmyqwsx5wktcd8cc3sq835lu7drv2xwl2wywfgse35a3x",
    "addr1w8phkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gtcyjy7wx",
    "addr1vx2fxv2umyhttkxyxp8x0dlpdt3k6cwng5pxj3jhsydzers66hrl8",
]

Match a transaction touching all of these at once:

[filters.predicate]
all = [
    "addr1w8phkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gtcyjy7wx",
    "stake178phkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gtcccycj5",
]

Mix entity types — here, an address that simultaneously holds an asset and carries a metadata label:

[filters.predicate]
all = [
    "addr1w8phkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gtcyjy7wx",
    "asset17jd78wukhtrnmjh3fngzasxm8rck0l2r4hhyyt",
    "#789",
]

Match against a single output’s contents (address, assets, and datum together):

[filters.predicate.match.output]
address = "addr1w8phkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gtcyjy7wx"
assets = ["asset17jd78wukhtrnmjh3fngzasxm8rck0l2r4hhyyt"]
datum = "datum1httkxyxp8x0dlpdt3k6cwng5pxj3j"

Metadata patterns

Match any transaction carrying a metadata label:

predicate = "#674"

Match on the content of metadata with a regular expression. The match recurses through arrays and maps (including map keys and values) and applies only to text metadata:

[filters.predicate.match.metadata]
label = 674


[filters.predicate.match.metadata.value.text]
regex = "(?i)hello.*world"  # case-insensitive