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src/examples/ logs.ts
TypeScript · 73 lines · 3 KB
10 *
11 * Columns (the trigger — generate this reader when a result has these types):
12 * ts DateTime
13 * level LowCardinality(String)
14 * service LowCardinality(String)
15 * message String
16 * trace_id String
17 *
18 * Four of the five columns are text consumed wholesale, and `LowCardinality(T)`
19 * is transparent in RowBinary (decodes as the inner `String`, no dictionary on
20 * the wire). A RowBinary string read is a varint length + `buf.toString("utf8",
21 * …)` per field in JS; V8's native `JSON.parse` builds the same JS strings in
22 * optimized C++ and tends to WIN here. This reader exists so the comparison is
23 * apples-to-apples — not because RowBinary is the right call for this shape.
24 */
25 export type LogRow = {
26 ts : Date ;
27 level : string ;
28 service : string ;
29 message : string ;
30 trace_id : string ;
31 };
32
33 /**
34 * API-combinator reader: one leaf reader per column, the clear default. There is
35 * little to monomorphize on a mostly-string row — the only fixed-width field is
36 * `ts` — so `readLogRowFast` below is barely different and barely faster; the
37 * real lesson (see `logs.bench.ts`) is that JSON beats both.
38 */
39 export const readLogRow : Reader < LogRow > = ( s ) => ({
40 ts: readDateTime (s),
41 level: readString (s), // LowCardinality(String) — transparent, decode as String
42 service: readString (s), // LowCardinality(String) — transparent, decode as String
43 message: readString (s),
44 trace_id: readString (s),
45 });
46
47 /**
48 * Optimized { @link readLogRow } : the four string reads inlined (varint length +
49 * `buf.toString` in place) and the `DateTime` read written out. Note how little
50 * monomorphization can do when the row is dominated by variable-length strings —
51 * there are no adjacent fixed-width columns to coalesce, so this stays close to
52 * the API version. Included to make `logs.bench.ts` a fair fight; the takeaway
53 * is to pick `JSONEachRow` for this shape, not to tune this reader.
54 */
55 export const readLogRowFast : Reader < LogRow > = ( s ) => {
56 const { buf } = s;
57 // DateTime: 4-byte LE Unix seconds.
58 const ts = new Date (s.view. getUint32 ( advance (s, 4 ), true ) * 1000 );
59 // Four UTF-8 Strings (the two LowCardinality columns are plain String on the wire).
60 let len = readUVarint (s);
61 let o = advance (s, len);
62 const level = buf. toString ( "utf8" , o, o + len);
63 len = readUVarint (s);
64 o = advance (s, len);
65 const service = buf. toString ( "utf8" , o, o + len);
66 len = readUVarint (s);
67 o = advance (s, len);
68 const message = buf. toString ( "utf8" , o, o + len);
69 len = readUVarint (s);
70 o = advance (s, len);
71 const trace_id = buf. toString ( "utf8" , o, o + len);
72 return { ts, level, service, message, trace_id };
73 };