Fix web impl streaming line breaks with large rows

CHANGELOG.md

@@ -1,5 +1,11 @@
 # 1.7.0 (Common, Node.js, Web)
 
+## Bug fixes
+
+- (Web only) Fixed an issue where streaming large datasets could provide corrupted results. See [#333](https://github.com/ClickHouse/clickhouse-js/pull/333) (PR) for more details.
+
+## New features
+
 - (Experimental) Exposed the `parseColumnType` function that takes a string representation of a ClickHouse type (e.g., `FixedString(16)`, `Nullable(Int32)`, etc.) and returns an AST-like object that represents the type. For example:
 
   ```ts

packages/client-common/__tests__/utils/datasets.ts

@@ -0,0 +1,37 @@
+import type { ClickHouseClient } from '@clickhouse/client-common'
+import { fakerRU } from '@faker-js/faker'
+import { createTableWithFields } from '@test/fixtures/table_with_fields'
+
+export async function genLargeStringsDataset<Stream = unknown>(
+  client: ClickHouseClient<Stream>,
+  {
+    rows,
+    words,
+  }: {
+    rows: number
+    words: number
+  },
+): Promise<{
+  table: string
+  values: { id: number; sentence: string; timestamp: string }[]
+}> {
+  const table = await createTableWithFields(
+    client as ClickHouseClient,
+    `sentence String, timestamp String`,
+  )
+  const values = [...new Array(rows)].map((_, id) => ({
+    id,
+    // it seems that it is easier to trigger an incorrect behavior with non-ASCII symbols
+    sentence: fakerRU.lorem.sentence(words),
+    timestamp: new Date().toISOString(),
+  }))
+  await client.insert({
+    table,
+    values,
+    format: 'JSONEachRow',
+  })
+  return {
+    table,
+    values,
+  }
+}

packages/client-node/__tests__/integration/node_streaming_e2e.test.ts

@@ -3,10 +3,9 @@ import {
   type ClickHouseClient,
   type ClickHouseSettings,
 } from '@clickhouse/client-common'
-import { fakerRU } from '@faker-js/faker'
 import { createSimpleTable } from '@test/fixtures/simple_table'
-import { createTableWithFields } from '@test/fixtures/table_with_fields'
 import { createTestClient, guid } from '@test/utils'
+import { genLargeStringsDataset } from '@test/utils/datasets'
 import { tableFromIPC } from 'apache-arrow'
 import { Buffer } from 'buffer'
 import Fs from 'fs'
@@ -152,40 +151,9 @@ describe('[Node.js] streaming e2e', () => {
   // Here we generate a large enough dataset to break into multiple chunks while streaming,
   // effectively testing the implementation of incomplete rows handling
   describe('should correctly process multiple chunks', () => {
-    async function generateData({
-      rows,
-      words,
-    }: {
-      rows: number
-      words: number
-    }): Promise<{
-      table: string
-      values: { id: number; sentence: string; timestamp: string }[]
-    }> {
-      const table = await createTableWithFields(
-        client as ClickHouseClient,
-        `sentence String, timestamp String`,
-      )
-      const values = [...new Array(rows)].map((_, id) => ({
-        id,
-        // it seems that it is easier to trigger an incorrect behavior with non-ASCII symbols
-        sentence: fakerRU.lorem.sentence(words),
-        timestamp: new Date().toISOString(),
-      }))
-      await client.insert({
-        table,
-        values,
-        format: 'JSONEachRow',
-      })
-      return {
-        table,
-        values,
-      }
-    }
-
     describe('large amount of rows', () => {
       it('should work with .json()', async () => {
-        const { table, values } = await generateData({
+        const { table, values } = await genLargeStringsDataset(client, {
           rows: 10000,
           words: 10,
         })
@@ -199,7 +167,7 @@ describe('[Node.js] streaming e2e', () => {
       })
 
       it('should work with .stream()', async () => {
-        const { table, values } = await generateData({
+        const { table, values } = await genLargeStringsDataset(client, {
           rows: 10000,
           words: 10,
         })
@@ -222,7 +190,7 @@ describe('[Node.js] streaming e2e', () => {
 
     describe("rows that don't fit into a single chunk", () => {
       it('should work with .json()', async () => {
-        const { table, values } = await generateData({
+        const { table, values } = await genLargeStringsDataset(client, {
           rows: 5,
           words: 10000,
         })
@@ -236,7 +204,7 @@ describe('[Node.js] streaming e2e', () => {
       })
 
       it('should work with .stream()', async () => {
-        const { table, values } = await generateData({
+        const { table, values } = await genLargeStringsDataset(client, {
           rows: 5,
           words: 10000,
         })

packages/client-web/__tests__/integration/web_select_streaming.test.ts

@@ -1,13 +1,21 @@
 import type { ClickHouseClient, Row } from '@clickhouse/client-common'
 import { createTestClient } from '@test/utils'
+import { genLargeStringsDataset } from '@test/utils/datasets'
 
 describe('[Web] SELECT streaming', () => {
   let client: ClickHouseClient<ReadableStream<Row[]>>
   afterEach(async () => {
     await client.close()
   })
   beforeEach(async () => {
-    client = createTestClient()
+    client = createTestClient({
+      // It is required to disable keep-alive to allow for larger inserts
+      // https://fetch.spec.whatwg.org/#http-network-or-cache-fetch
+      // If contentLength is non-null and httpRequest’s keepalive is true, then:
+      // <...>
+      // If the sum of contentLength and inflightKeepaliveBytes is greater than 64 kibibytes, then return a network error.
+      keep_alive: { enabled: false },
+    })
   })
 
   describe('consume the response only once', () => {
@@ -199,6 +207,75 @@ describe('[Web] SELECT streaming', () => {
       ])
     })
   })
+
+  // See https://github.com/ClickHouse/clickhouse-js/issues/171 for more details
+  // Here we generate a large enough dataset to break into multiple chunks while streaming,
+  // effectively testing the implementation of incomplete rows handling
+  describe('should correctly process multiple chunks', () => {
+    describe('large amount of rows', () => {
+      it('should work with .json()', async () => {
+        const { table, values } = await genLargeStringsDataset(client, {
+          rows: 10000,
+          words: 10,
+        })
+        const result = await client
+          .query({
+            query: `SELECT * FROM ${table} ORDER BY id ASC`,
+            format: 'JSONEachRow',
+          })
+          .then((r) => r.json())
+        expect(result).toEqual(values)
+      })
+
+      it('should work with .stream()', async () => {
+        const { table, values } = await genLargeStringsDataset(client, {
+          rows: 10000,
+          words: 10,
+        })
+        const stream = await client
+          .query({
+            query: `SELECT * FROM ${table} ORDER BY id ASC`,
+            format: 'JSONEachRow',
+          })
+          .then((r) => r.stream())
+
+        const result = await rowsJsonValues(stream)
+        expect(result).toEqual(values)
+      })
+    })
+
+    describe("rows that don't fit into a single chunk", () => {
+      it('should work with .json()', async () => {
+        const { table, values } = await genLargeStringsDataset(client, {
+          rows: 5,
+          words: 10000,
+        })
+        const result = await client
+          .query({
+            query: `SELECT * FROM ${table} ORDER BY id ASC`,
+            format: 'JSONEachRow',
+          })
+          .then((r) => r.json())
+        expect(result).toEqual(values)
+      })
+
+      it('should work with .stream()', async () => {
+        const { table, values } = await genLargeStringsDataset(client, {
+          rows: 5,
+          words: 10000,
+        })
+        const stream = await client
+          .query({
+            query: `SELECT * FROM ${table} ORDER BY id ASC`,
+            format: 'JSONEachRow',
+          })
+          .then((r) => r.stream())
+
+        const result = await rowsJsonValues(stream)
+        expect(result).toEqual(values)
+      })
+    })
+  })
 })
 
 async function rowsJsonValues<T = unknown>(

packages/client-web/src/result_set.ts

@@ -9,10 +9,12 @@ import type {
 import {
   isNotStreamableJSONFamily,
   isStreamableJSONFamily,
+  validateStreamFormat,
 } from '@clickhouse/client-common'
-import { validateStreamFormat } from '@clickhouse/client-common'
 import { getAsText } from './utils'
 
+const NEWLINE = 0x0a as const
+
 export class ResultSet<Format extends DataFormat | unknown>
   implements BaseResultSet<ReadableStream<Row[]>, Format>
 {
@@ -67,40 +69,67 @@ export class ResultSet<Format extends DataFormat | unknown>
     this.markAsConsumed()
     validateStreamFormat(this.format)
 
-    let decodedChunk = ''
+    let incompleteChunks: Uint8Array[] = []
+    let totalIncompleteLength = 0
     const decoder = new TextDecoder('utf-8')
     const transform = new TransformStream({
       start() {
         //
       },
-      transform: (chunk, controller) => {
+      transform: (chunk: Uint8Array, controller) => {
         if (chunk === null) {
           controller.terminate()
         }
-        decodedChunk += decoder.decode(chunk)
         const rows: Row[] = []
-        // eslint-disable-next-line no-constant-condition
-        while (true) {
-          const idx = decodedChunk.indexOf('\n')
-          if (idx !== -1) {
-            const text = decodedChunk.slice(0, idx)
-            decodedChunk = decodedChunk.slice(idx + 1)
+        let idx: number
+        let lastIdx = 0
+        do {
+          // an unescaped newline character denotes the end of a row
+          idx = chunk.indexOf(NEWLINE, lastIdx)
+          // there is no complete row in the rest of the current chunk
+          if (idx === -1) {
+            // to be processed during the next transform iteration
+            const incompleteChunk = chunk.slice(lastIdx)
+            incompleteChunks.push(incompleteChunk)
+            totalIncompleteLength += incompleteChunk.length
+            // send the extracted rows to the consumer, if any
+            if (rows.length > 0) {
+              controller.enqueue(rows)
+            }
+          } else {
+            let text: string
+            if (incompleteChunks.length > 0) {
+              const completeRowBytes = new Uint8Array(
+                totalIncompleteLength + idx,
+              )
+
+              // using the incomplete chunks from the previous iterations
+              let offset = 0
+              incompleteChunks.forEach((incompleteChunk) => {
+                completeRowBytes.set(incompleteChunk, offset)
+                offset += incompleteChunk.length
+              })
+              // finalize the row with the current chunk slice that ends with a newline
+              const finalChunk = chunk.slice(0, idx)
+              completeRowBytes.set(finalChunk, offset)
+
+              // reset the incomplete chunks
+              incompleteChunks = []
+              totalIncompleteLength = 0
+
+              text = decoder.decode(completeRowBytes)
+            } else {
+              text = decoder.decode(chunk.slice(lastIdx, idx))
+            }
             rows.push({
               text,
               json<T>(): T {
                 return JSON.parse(text)
               },
             })
-          } else {
-            if (rows.length) {
-              controller.enqueue(rows)
-            }
-            break
+            lastIdx = idx + 1 // skipping newline character
           }
-        }
-      },
-      flush() {
-        decodedChunk = ''
+        } while (idx !== -1)
       },
     })