persist: read-side query helpers — seq/time/type/predicate scans + 9 tests

query.sx: read-between (seq range), read-since/read-window (by :at),
read-by-type, read-where, count-where. Pure scans over persist/read for audit
windows, type filters, since-cursors. 152/152.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/persist/conformance.sh

@@ -13,7 +13,7 @@ if [ ! -x "$SX_SERVER" ]; then
   exit 1
 fi
 
-SUITES=(event log kv project subscribe concurrency snapshot compaction durable blob view cas catalog recovery)
+SUITES=(event log kv project subscribe concurrency snapshot compaction durable blob view cas catalog query recovery)
 
 OUT_JSON="lib/persist/scoreboard.json"
 OUT_MD="lib/persist/scoreboard.md"
@@ -39,6 +39,7 @@ run_suite() {
 (load "lib/persist/blob.sx")
 (load "lib/persist/view.sx")
 (load "lib/persist/catalog.sx")
+(load "lib/persist/query.sx")
 (load "lib/persist/subscribe.sx")
 (load "lib/persist/api.sx")
 (epoch 2)

lib/persist/query.sx

@@ -0,0 +1,54 @@
+; persist/query — read-side helpers over a stream: slice by seq range, filter by
+; timestamp / type / predicate. Pure reads composed from persist/read, no
+; backend changes. The log is bad at ad-hoc relational queries (project into a
+; kv read model for those) but these cover the common log scans: an audit window
+; by time, a type filter, a since-cursor for incremental consumers.
+; Requires: lib/persist/log.sx.
+
+; events with seq in [from, to] inclusive
+(define
+  persist/read-between
+  (fn
+    (b stream from to)
+    (filter
+      (fn
+        (e)
+        (and (>= (persist/event-seq e) from) (<= (persist/event-seq e) to)))
+      (persist/read b stream))))
+
+; events at or after a timestamp (events carry :at; never a clock here)
+(define
+  persist/read-since
+  (fn
+    (b stream at)
+    (filter (fn (e) (>= (persist/event-at e) at)) (persist/read b stream))))
+
+; events whose :at is in [from, to] inclusive — an audit window
+(define
+  persist/read-window
+  (fn
+    (b stream from to)
+    (filter
+      (fn
+        (e)
+        (and (>= (persist/event-at e) from) (<= (persist/event-at e) to)))
+      (persist/read b stream))))
+
+; events matching a predicate (e -> truthy)
+(define
+  persist/read-where
+  (fn (b stream pred) (filter pred (persist/read b stream))))
+
+; events of a given type
+(define
+  persist/read-by-type
+  (fn
+    (b stream type)
+    (filter
+      (fn (e) (equal? (persist/event-type e) type))
+      (persist/read b stream))))
+
+; count events matching a predicate
+(define
+  persist/count-where
+  (fn (b stream pred) (len (persist/read-where b stream pred))))

lib/persist/scoreboard.json

@@ -13,9 +13,10 @@
     "view": {"pass": 11, "fail": 0},
     "cas": {"pass": 11, "fail": 0},
     "catalog": {"pass": 10, "fail": 0},
+    "query": {"pass": 9, "fail": 0},
     "recovery": {"pass": 6, "fail": 0}
   },
-  "total_pass": 143,
+  "total_pass": 152,
   "total_fail": 0,
-  "total": 143
+  "total": 152
 }

lib/persist/scoreboard.md

@@ -17,5 +17,6 @@ _Generated by `lib/persist/conformance.sh`_
 | view | 11 | 0 | 11 |
 | cas | 11 | 0 | 11 |
 | catalog | 10 | 0 | 10 |
+| query | 9 | 0 | 9 |
 | recovery | 6 | 0 | 6 |
-| **Total** | **143** | **0** | **143** |
+| **Total** | **152** | **0** | **152** |

lib/persist/tests/query.sx

@@ -0,0 +1,101 @@
+; Extension — read-side query helpers. Assertions count / index, not map vs list.
+
+(define q-seqs (fn (es) (map persist/event-seq es)))
+
+(persist-test
+  "read-between slices a seq range"
+  (let
+    ((b (persist/open)))
+    (begin
+      (persist/append b "s" "x" 0 {})
+      (persist/append b "s" "x" 0 {})
+      (persist/append b "s" "x" 0 {})
+      (persist/append b "s" "x" 0 {})
+      (let
+        ((es (persist/read-between b "s" 2 3)))
+        (list
+          (len es)
+          (persist/event-seq (first es))
+          (persist/event-seq (nth es 1))))))
+  (list 2 2 3))
+(persist-test
+  "read-between is inclusive of endpoints"
+  (let
+    ((b (persist/open)))
+    (begin
+      (persist/append b "s" "x" 0 {})
+      (persist/append b "s" "x" 0 {})
+      (persist/append b "s" "x" 0 {})
+      (len (persist/read-between b "s" 1 3))))
+  3)
+(persist-test
+  "read-since filters by timestamp"
+  (let
+    ((b (persist/open)))
+    (begin
+      (persist/append b "s" "x" 100 {})
+      (persist/append b "s" "x" 200 {})
+      (persist/append b "s" "x" 300 {})
+      (len (persist/read-since b "s" 200))))
+  2)
+(persist-test
+  "read-window is an inclusive time range"
+  (let
+    ((b (persist/open)))
+    (begin
+      (persist/append b "s" "x" 100 {})
+      (persist/append b "s" "x" 200 {})
+      (persist/append b "s" "x" 300 {})
+      (persist/append b "s" "x" 400 {})
+      (len (persist/read-window b "s" 200 300))))
+  2)
+(persist-test
+  "read-by-type filters by event type"
+  (let
+    ((b (persist/open)))
+    (begin
+      (persist/append b "s" "created" 0 {})
+      (persist/append b "s" "updated" 0 {})
+      (persist/append b "s" "created" 0 {})
+      (len (persist/read-by-type b "s" "created"))))
+  2)
+(persist-test
+  "read-where filters by predicate over data"
+  (let
+    ((b (persist/open)))
+    (begin
+      (persist/append b "s" "x" 0 {:amt 5})
+      (persist/append b "s" "x" 0 {:amt 15})
+      (persist/append b "s" "x" 0 {:amt 25})
+      (len
+        (persist/read-where
+          b
+          "s"
+          (fn (e) (> (get (persist/event-data e) :amt) 10))))))
+  2)
+(persist-test
+  "count-where counts matches"
+  (let
+    ((b (persist/open)))
+    (begin
+      (persist/append b "s" "a" 0 {})
+      (persist/append b "s" "b" 0 {})
+      (persist/append b "s" "a" 0 {})
+      (persist/count-where
+        b
+        "s"
+        (fn (e) (equal? (persist/event-type e) "a")))))
+  2)
+(persist-test
+  "queries return empty on empty stream"
+  (len (persist/read-since (persist/open) "s" 0))
+  0)
+(persist-test
+  "queries work on the durable backend"
+  (let
+    ((db (persist/mock-durable (persist/mem-backend))))
+    (begin
+      (persist/append db "s" "x" 100 {})
+      (persist/append db "s" "x" 200 {})
+      (len (persist/read-since db "s" 150))))
+  1)