From 7d8521af8ca6e01d9a521272d0409bce52d1ce7c Mon Sep 17 00:00:00 2001
From: Bob den Os <108393871+BobdenOs@users.noreply.github.com>
Date: Wed, 29 Nov 2023 09:18:34 +0100
Subject: [PATCH] fix: large amounts of expands in HANA Service (#355)

Co-authored-by: Johannes Vogel <31311694+johannes-vogel@users.noreply.github.com>
---
 hana/lib/HANAService.js  |  3 ++-
 hana/lib/drivers/base.js | 17 ++++++++++-------
 hana/lib/drivers/hdb.js  | 30 ++++++++++++++++++++----------
 3 files changed, 32 insertions(+), 18 deletions(-)

diff --git a/hana/lib/HANAService.js b/hana/lib/HANAService.js
index 3d8cb2ecb..03e45f402 100644
--- a/hana/lib/HANAService.js
+++ b/hana/lib/HANAService.js
@@ -180,7 +180,8 @@ class HANAService extends SQLService {
             })
             break
           } else {
-            level.data.push(data)
+            // REVISIT: identify why sometimes not all parent rows are returned
+            level.data.push?.(data)
             levels.push({
               data: data,
               path: row._path_,
diff --git a/hana/lib/drivers/base.js b/hana/lib/drivers/base.js
index b2dd83d06..127afff21 100644
--- a/hana/lib/drivers/base.js
+++ b/hana/lib/drivers/base.js
@@ -222,10 +222,11 @@ const handleLevel = function (levels, path, expands) {
           path: path.slice(0, -6),
           expands,
         })
+      } else {
+        // Current row is on the same level now so incrementing the index
+        // If the index was not 0 it should add a comma
+        if (level.index++) buffer += ','
       }
-      // Current row is on the same level now so incrementing the index
-      // If the index was not 0 it should add a comma
-      if (level.index++) buffer += ','
       levels.push({
         index: 0,
         suffix: '}',
@@ -236,10 +237,12 @@ const handleLevel = function (levels, path, expands) {
     } else {
       // Step up if it is not a child of the current level
       const level = levels.pop()
-      const leftOverExpands = Object.keys(level.expands)
-      // Fill in all missing expands
-      if (leftOverExpands.length) {
-        buffer += leftOverExpands.map(p => `${JSON.stringify(p)}:${JSON.stringify(level.expands[p])}`).join(',')
+      if (level.suffix === '}') {
+        const leftOverExpands = Object.keys(level.expands)
+        // Fill in all missing expands
+        if (leftOverExpands.length) {
+          buffer += (level.hasProperties ? ',' : '') + leftOverExpands.map(p => `${JSON.stringify(p)}:${JSON.stringify(level.expands[p])}`).join(',')
+        }
       }
       if (level.suffix) buffer += level.suffix
     }
diff --git a/hana/lib/drivers/hdb.js b/hana/lib/drivers/hdb.js
index fcf2543b7..6c7e4e441 100644
--- a/hana/lib/drivers/hdb.js
+++ b/hana/lib/drivers/hdb.js
@@ -55,7 +55,7 @@ class HDBDriver extends driver {
     const ret = await super.prepare(sql)
     ret.stream = async (values, one) => {
       const stmt = await ret._prep
-      const rs = await prom(stmt, 'execute')(values)
+      const rs = await prom(stmt, 'execute')(values || [])
       const cols = rs.metadata
       // If the query only returns a single row with a single blob it is the final stream
       if (cols.length === 1 && cols[0].length === -1) {
@@ -129,6 +129,10 @@ async function* rsIterator(rs, one) {
           this.reading = 0
           this.writing = 0
         })
+          .catch(e => {
+            // TODO: check whether the error is early close
+            return true
+          })
       }
     },
     ensure(size) {
@@ -251,8 +255,9 @@ async function* rsIterator(rs, one) {
 
     state.inject(handleLevel(levels, path, expands))
 
+    // REVISIT: allow streaming with both NVARCHAR and NCLOB
     // Read and write JSON blob data
-    const jsonLength = readBlob(state)
+    const jsonLength = readString(state, true)
     let hasProperties = (typeof jsonLength === 'number' ? jsonLength : await jsonLength) > 2
 
     for (const blobColumn of nativeBlobs) {
@@ -304,9 +309,9 @@ async function* rsIterator(rs, one) {
   rs.close()
 }
 
-const readString = function (state) {
+const readString = function (state, isJson = false) {
   let ens = state.ensure(1)
-  if (ens) return ens.then(() => readString(state))
+  if (ens) return ens.then(() => readString(state, isJson))
 
   let length = state.buffer[state.reading]
   let offset = 1
@@ -315,21 +320,26 @@ const readString = function (state) {
       throw new Error('Missing stream metadata')
     case 0xf6:
       ens = state.ensure(2)
-      if (ens) return ens.then(() => readString(state))
-      length = state.buffer.readInt16LE(state.reading)
-      offset = 2
+      if (ens) return ens.then(() => readString(state, isJson))
+      length = state.buffer.readInt16LE(state.reading + offset)
+      offset += 2
       break
     case 0xf7:
       ens = state.ensure(4)
-      if (ens) return ens.then(() => readString(state))
-      length = state.buffer.readInt32LE(state.reading)
-      offset = 4
+      if (ens) return ens.then(() => readString(state, isJson))
+      length = state.buffer.readInt32LE(state.reading + offset)
+      offset += 4
       break
     default:
   }
 
   // Read the string value
   state.read(offset)
+  if (isJson) {
+    state.write(length - 1)
+    state.read(1)
+    return length
+  }
   return state.slice(length)
 }