ORC-1012: Support specifying columns in orc-scan (#921)

### What changes were proposed in this pull request?

The PR adds an option to support specifying columns to be read in the orc-scan tool.

### Why are the changes needed?

Currently the orc-scan tool will scan all columns. I find it useful to specifying columns when profiling read performance on specified data types.

### How was this patch tested?

Manually tested with the new option.
Added tests in tools/test/TestFileScan.cc.

tools/src/FileScan.cc

@@ -26,11 +26,12 @@
 #include <iostream>
 #include <string>
 
-void scanFile(std::ostream & out, const char* filename, uint64_t batchSize) {
+void scanFile(std::ostream & out, const char* filename, uint64_t batchSize,
+              const orc::RowReaderOptions& rowReaderOpts) {
   orc::ReaderOptions readerOpts;
   std::unique_ptr<orc::Reader> reader =
     orc::createReader(orc::readFile(filename), readerOpts);
-  std::unique_ptr<orc::RowReader> rowReader = reader->createRowReader();
+  std::unique_ptr<orc::RowReader> rowReader = reader->createRowReader(rowReaderOpts);
   std::unique_ptr<orc::ColumnVectorBatch> batch =
     rowReader->createRowBatch(batchSize);
 
@@ -48,14 +49,17 @@ int main(int argc, char* argv[]) {
   static struct option longOptions[] = {
     {"help", no_argument, ORC_NULLPTR, 'h'},
     {"batch", required_argument, ORC_NULLPTR, 'b'},
+    {"columns", required_argument, ORC_NULLPTR, 'c'},
     {ORC_NULLPTR, 0, ORC_NULLPTR, 0}
   };
   bool helpFlag = false;
   uint64_t batchSize = 1024;
+  std::list<uint64_t> cols;
+  orc::RowReaderOptions rowReaderOptions;
   int opt;
   char *tail;
   do {
-    opt = getopt_long(argc, argv, "hb:", longOptions, ORC_NULLPTR);
+    opt = getopt_long(argc, argv, "hb:c:", longOptions, ORC_NULLPTR);
     switch (opt) {
     case '?':
     case 'h':
@@ -69,19 +73,32 @@ int main(int argc, char* argv[]) {
         return 1;
       }
       break;
+    case 'c': {
+      char *col = std::strtok(optarg, ",");
+      while (col) {
+        cols.push_back(static_cast<uint64_t>(std::atoi(col)));
+        col = std::strtok(ORC_NULLPTR, ",");
+      }
+      if (!cols.empty()) {
+        rowReaderOptions.include(cols);
+      }
+      break;
+    }
+    default: break;
     }
   } while (opt != -1);
   argc -= optind;
   argv += optind;
 
   if (argc < 1 || helpFlag) {
     std::cerr << "Usage: orc-scan [-h] [--help]\n"
+              << "                [-c 1,2,...] [--columns=1,2,...]\n"
               << "                [-b<size>] [--batch=<size>] <filename>\n";
     return 1;
   } else {
     for(int i=0; i < argc; ++i) {
       try {
-        scanFile(std::cout, argv[i], batchSize);
+        scanFile(std::cout, argv[i], batchSize, rowReaderOptions);
       } catch (std::exception& ex) {
         std::cerr << "Caught exception in " << argv[i]
                   << ": " << ex.what() << "\n";

tools/test/TestFileScan.cc

@@ -34,11 +34,22 @@ TEST (TestFileScan, testNominal) {
   EXPECT_EQ("Rows: 32768\nBatches: 33\n", output);
   EXPECT_EQ("", error);
 
+  EXPECT_EQ(0, runProgram({pgm, std::string("-c"), std::string("1,2,3,9"), file},
+                          output, error));
+  EXPECT_EQ("Rows: 32768\nBatches: 33\n", output);
+  EXPECT_EQ("", error);
+
   EXPECT_EQ(0, runProgram({pgm, std::string("-b"), std::string("256"), file},
                           output, error));
   EXPECT_EQ("Rows: 32768\nBatches: 131\n", output);
   EXPECT_EQ("", error);
 
+  EXPECT_EQ(0, runProgram({pgm, std::string("-b"), std::string("256"),
+                           std::string("-c"), std::string("1,2,3"), file},
+                          output, error));
+  EXPECT_EQ("Rows: 32768\nBatches: 131\n", output);
+  EXPECT_EQ("", error);
+
   EXPECT_EQ(0, runProgram({pgm, std::string("-b256"), file}, output, error));
   EXPECT_EQ("Rows: 32768\nBatches: 131\n", output);
   EXPECT_EQ("", error);
@@ -52,6 +63,11 @@ TEST (TestFileScan, testNominal) {
                           output, error));
   EXPECT_EQ("Rows: 32768\nBatches: 131\n", output);
   EXPECT_EQ("", error);
+
+  EXPECT_EQ(0, runProgram({pgm, std::string("--batch=256"),
+                           std::string("--columns=1,2,3"), file},output, error));
+  EXPECT_EQ("Rows: 32768\nBatches: 131\n", output);
+  EXPECT_EQ("", error);
 }
 
 /**
@@ -104,6 +120,7 @@ TEST (TestFileScan, testBadCommand) {
   EXPECT_EQ("", output);
   EXPECT_EQ("orc-scan: option requires an argument -- b\n"
             "Usage: orc-scan [-h] [--help]\n"
+            "                [-c 1,2,...] [--columns=1,2,...]\n"
             "                [-b<size>] [--batch=<size>] <filename>\n",
             removeChars(stripPrefix(error, "orc-scan: "),"'`"));
 
@@ -122,6 +139,7 @@ TEST (TestFileScan, testBadCommand) {
   EXPECT_EQ("", output);
   EXPECT_EQ("orc-scan: option --batch requires an argument\n"
             "Usage: orc-scan [-h] [--help]\n"
+            "                [-c 1,2,...] [--columns=1,2,...]\n"
             "                [-b<size>] [--batch=<size>] <filename>\n",
             removeChars(stripPrefix(error, "orc-scan: "), "'`"));