better usage of __isStreamHeader flag

packages/api/src/shell/copyStream.js

@@ -2,12 +2,17 @@ const EnsureStreamHeaderStream = require('../utility/EnsureStreamHeaderStream');
 
 function copyStream(input, output) {
   return new Promise((resolve, reject) => {
-    const ensureHeader = new EnsureStreamHeaderStream();
     const finisher = output['finisher'] || output;
     finisher.on('finish', resolve);
     finisher.on('error', reject);
-    input.pipe(ensureHeader);
-    ensureHeader.pipe(output);
+
+    if (output.requireFixedStructure) {
+      const ensureHeader = new EnsureStreamHeaderStream();
+      input.pipe(ensureHeader);
+      ensureHeader.pipe(output);
+    } else {
+      input.pipe(output);
+    }
   });
 }
 

packages/api/src/shell/jsonArrayWriter.js

@@ -11,10 +11,7 @@ class StringifyStream extends stream.Transform {
     let skip = false;
 
     if (!this.wasHeader) {
-      skip =
-        chunk.__isStreamHeader ||
-        // TODO remove isArray test
-        Array.isArray(chunk.columns);
+      skip = chunk.__isStreamHeader;
       this.wasHeader = true;
     }
     if (!skip) {

packages/api/src/shell/jsonLinesReader.js

@@ -12,14 +12,14 @@ class ParseStream extends stream.Transform {
   _transform(chunk, encoding, done) {
     const obj = JSON.parse(chunk);
     if (!this.wasHeader) {
-      if (
-        !obj.__isStreamHeader &&
-        // TODO remove isArray test
-        !Array.isArray(obj.columns)
-      ) {
-        this.push({ columns: Object.keys(obj).map(columnName => ({ columnName })) });
+      if (!obj.__isStreamHeader) {
+        this.push({
+          __isStreamHeader: true,
+          __isDynamicStructure: true,
+          // columns: Object.keys(obj).map(columnName => ({ columnName })),
+        });
       }
-      
+
       this.wasHeader = true;
     }
     if (!this.limitRows || this.rowsWritten < this.limitRows) {

packages/api/src/shell/jsonLinesWriter.js

@@ -10,11 +10,7 @@ class StringifyStream extends stream.Transform {
   _transform(chunk, encoding, done) {
     let skip = false;
     if (!this.wasHeader) {
-      skip =
-        (chunk.__isStreamHeader ||
-          // TODO remove isArray test
-          Array.isArray(chunk.columns)) &&
-        !this.header;
+      skip = (chunk.__isStreamHeader && !this.header) || (chunk.__isStreamHeader && chunk.__isDynamicStructure);
       this.wasHeader = true;
     }
     if (!skip) {

packages/api/src/shell/sqlDataWriter.js

@@ -14,11 +14,7 @@ class SqlizeStream extends stream.Transform {
   _transform(chunk, encoding, done) {
     let skip = false;
     if (!this.wasHeader) {
-      if (
-        chunk.__isStreamHeader ||
-        // TODO remove isArray test
-        Array.isArray(chunk.columns)
-      ) {
+      if (chunk.__isStreamHeader) {
         skip = true;
         this.tableName = chunk.pureName;
         if (chunk.engine) {

packages/api/src/utility/EnsureStreamHeaderStream.js

@@ -13,11 +13,7 @@ class EnsureStreamHeaderStream extends stream.Transform {
         return;
       }
 
-      if (
-        !chunk.__isStreamHeader &&
-        // TODO remove isArray test
-        !Array.isArray(chunk.columns)
-      ) {
+      if (!chunk.__isStreamHeader) {
         this.push({
           __isStreamHeader: true,
           __isComputedStructure: true,