Cache clauses -> row group mapping

Create a shadow table. For `stats`, it'd be `_stats_rowgroups`.

It contains three columns:

- the clause (eg `city = 'Dawson Creek'`)
- the initial estimate, as a bitmap of rowgroups based on stats
- the actual observed rowgroups, as a bitmap

This papers over poorly sorted parquet files, at the cost of some disk
space. It makes interactive queries much more natural -- drilldown style
queries are much faster, as they can leverage work done by previous
queries.

eg 'SELECT * FROM stats WHERE city = 'Dawson Creek' and question_id >= 1935 and question_id <= 1940`
takes ~584ms on first run, but 9ms on subsequent runs.

We only create entries when the estimates don't match the actual
results.

Fixes #6

README.md

@@ -72,6 +72,18 @@ constraints before returning control to SQLite's virtual machine. This minimizes
 the number of allocations performed when many rows are filtered out by
 the user's criteria.
 
+### Memoized slices
+
+Individual clauses are mapped to the row groups they match.
+
+eg going on row group statistics, which store minimum and maximum values, a clause
+like `WHERE city = 'Dawson Creek'` may match 80% of row groups.
+
+In reality, it may only be present in one or two row groups.
+
+This is recorded in a shadow table so future queries that contain that clause
+can read only the necessary row groups.
+
 ### Types
 
 These Parquet types are supported:

parquet/parquet.cc

@@ -17,6 +17,7 @@ SQLITE_EXTENSION_INIT1
 #include <stdarg.h>
 #include <ctype.h>
 #include <stdio.h>
+#include <iomanip>
 
 #include <memory>
 
@@ -32,6 +33,7 @@ static int parquetConnect(sqlite3*, void*, int, const char*const*,
                            sqlite3_vtab**,char**);
 static int parquetBestIndex(sqlite3_vtab*,sqlite3_index_info*);
 static int parquetDisconnect(sqlite3_vtab*);
+static int parquetDestroy(sqlite3_vtab*);
 static int parquetOpen(sqlite3_vtab*, sqlite3_vtab_cursor**);
 static int parquetClose(sqlite3_vtab_cursor*);
 static int parquetFilter(sqlite3_vtab_cursor*, int idxNum, const char *idxStr,
@@ -45,6 +47,7 @@ static int parquetRowid(sqlite3_vtab_cursor*,sqlite3_int64*);
 typedef struct sqlite3_vtab_parquet {
   sqlite3_vtab base;              /* Base class.  Must be first */
   ParquetTable* table;
+  sqlite3* db;
 } sqlite3_vtab_parquet;
 
 
@@ -54,6 +57,21 @@ typedef struct sqlite3_vtab_cursor_parquet {
   ParquetCursor* cursor;
 } sqlite3_vtab_cursor_parquet;
 
+static int parquetDestroy(sqlite3_vtab *pVtab) {
+  sqlite3_vtab_parquet *p = (sqlite3_vtab_parquet*)pVtab;
+
+  // Clean up our shadow table. This is useful if the user has recreated
+  // the parquet file, and our mappings would now be invalid.
+  std::string drop = "DROP TABLE IF EXISTS _";
+  drop.append(p->table->getTableName());
+  drop.append("_rowgroups");
+  int rv = sqlite3_exec(p->db, drop.data(), 0, 0, 0);
+  if(rv != 0)
+    return rv;
+
+  return SQLITE_OK;
+}
+
 /*
 ** This method is the destructor fo a sqlite3_vtab_parquet object.
 */
@@ -78,6 +96,7 @@ static int parquetConnect(
       return SQLITE_ERROR;
     }
 
+    std::string tableName = argv[2];
     // Remove the delimiting single quotes
     std::string fname = argv[3];
     fname = fname.substr(1, fname.length() - 2);
@@ -87,7 +106,7 @@ static int parquetConnect(
     memset(vtab.get(), 0, sizeof(*vtab.get()));
 
     try {
-      std::unique_ptr<ParquetTable> table(new ParquetTable(fname));
+      std::unique_ptr<ParquetTable> table(new ParquetTable(fname, tableName));
 
       std::string create = table->CreateStatement();
       int rc = sqlite3_declare_vtab(db, create.data());
@@ -95,6 +114,7 @@ static int parquetConnect(
         return rc;
 
       vtab->table = table.release();
+      vtab->db = db;
       *ppVtab = (sqlite3_vtab*)vtab.release();
       return SQLITE_OK;
     } catch (const std::exception& e) {
@@ -119,16 +139,81 @@ static int parquetCreate(
   sqlite3_vtab **ppVtab,
   char **pzErr
 ){
+  try {
+    // Create shadow table for storing constraint -> rowid mappings
+    std::string create = "CREATE TABLE IF NOT EXISTS _";
+    create.append(argv[2]);
+    create.append("_rowgroups(clause TEXT, estimate BLOB, actual BLOB)");
+    int rv = sqlite3_exec(db, create.data(), 0, 0, 0);
+    if(rv != 0)
+      return rv;
+
+    create = "CREATE UNIQUE INDEX IF NOT EXISTS _";
+    create.append(argv[2]);
+    create.append("_index ON _");
+    create.append(argv[2]);
+    create.append("_rowgroups(clause)");
+    rv = sqlite3_exec(db, create.data(), 0, 0, 0);
+
     return parquetConnect(db, pAux, argc, argv, ppVtab, pzErr);
+  } catch (std::bad_alloc& ba) {
+    return SQLITE_NOMEM;
+  }
 }
 
+std::string quoteBlob(const std::vector<unsigned char>& bytes) {
+  std::ostringstream ss;
+  ss << "X'" << std::hex;
+  for(unsigned int i = 0; i < bytes.size(); i++) {
+    ss << std::setfill('0') << std::setw(2) << (unsigned int)(unsigned char)bytes[i];
+  }
+  ss << "'";
+
+  return ss.str();
+}
+
+void persistConstraints(sqlite3* db, ParquetCursor* cursor) {
+  for(unsigned int i = 0; i < cursor->getNumConstraints(); i++) {
+    const Constraint& constraint = cursor->getConstraint(i);
+    const std::vector<unsigned char>& estimated = constraint.bitmap.estimatedMembership;
+    const std::vector<unsigned char>& actual = constraint.bitmap.actualMembership;
+    if(estimated == actual) {
+      continue;
+    }
+    std::string desc = constraint.describe();
+
+    std::string estimatedStr = quoteBlob(estimated);
+    std::string actualStr = quoteBlob(actual);
+
+    // This is only advisory, so ignore failures.
+    char* sql = sqlite3_mprintf(
+        "INSERT OR REPLACE INTO _%s_rowgroups(clause, estimate, actual) VALUES ('%q', %s, %s)",
+        cursor->getTable()->getTableName().c_str(),
+        desc.c_str(),
+        estimatedStr.c_str(),
+        actualStr.c_str());
+
+
+    if(sql == NULL)
+      return;
+
+    sqlite3_exec(db, sql, 0, 0, 0);
+    sqlite3_free(sql);
+  }
+}
+
+
 /*
 ** Destructor for a sqlite3_vtab_cursor_parquet.
 */
 static int parquetClose(sqlite3_vtab_cursor *cur){
-  sqlite3_vtab_cursor_parquet* p = (sqlite3_vtab_cursor_parquet*)cur;
+  sqlite3_vtab_cursor_parquet* vtab_cursor_parquet = (sqlite3_vtab_cursor_parquet*)cur;
-  p->cursor->close();
+  sqlite3_vtab_parquet* vtab_parquet = (sqlite3_vtab_parquet*)(vtab_cursor_parquet->base.pVtab);
-  delete p->cursor;
+  ParquetCursor* cursor = vtab_cursor_parquet->cursor;
+  persistConstraints(vtab_parquet->db, cursor);
+
+  vtab_cursor_parquet->cursor->close();
+  delete vtab_cursor_parquet->cursor;
   sqlite3_free(cur);
   return SQLITE_OK;
 }
@@ -196,7 +281,8 @@ const char* opName(int op) {
 */
 static int parquetNext(sqlite3_vtab_cursor *cur){
   try {
-    ParquetCursor* cursor = ((sqlite3_vtab_cursor_parquet*)cur)->cursor;
+    sqlite3_vtab_cursor_parquet* vtab_cursor_parquet = (sqlite3_vtab_cursor_parquet*)cur;
+    ParquetCursor* cursor = vtab_cursor_parquet->cursor;
     cursor->next();
     return SQLITE_OK;
   } catch(std::bad_alloc& ba) {
@@ -395,6 +481,38 @@ ConstraintOperator constraintOperatorFromSqlite(int op) {
   throw std::invalid_argument(ss.str());
 }
 
+std::vector<unsigned char> getRowGroupsForClause(sqlite3* db, std::string table, std::string clause) {
+  std::vector<unsigned char> rv;
+
+  std::unique_ptr<char, void(*)(void*)> sql(sqlite3_mprintf(
+      "SELECT actual FROM _%s_rowgroups WHERE clause = '%q'",
+      table.c_str(),
+      clause.c_str()), sqlite3_free);
+
+  if(sql.get() == NULL)
+    return rv;
+
+  sqlite3_stmt* pStmt = NULL;
+  int rc = sqlite3_prepare_v2(db, sql.get(), -1, &pStmt, NULL);
+  if(rc != 0)
+    return rv;
+
+  rc = sqlite3_step(pStmt);
+  if(rc == SQLITE_ROW) {
+    int size = sqlite3_column_bytes(pStmt, 0);
+    unsigned char* blob = (unsigned char*)sqlite3_column_blob(pStmt, 0);
+    // TODO: there is a memory leak here if we get a std::bad_alloc while populating rv;
+    // we fail to free pStmt
+    for(int i = 0; i < size; i++) {
+      rv.push_back(blob[i]);
+    }
+  }
+
+  sqlite3_finalize(pStmt);
+  return rv;
+}
+
+
 /*
 ** Only a full table scan is supported.  So xFilter simply rewinds to
 ** the beginning.
@@ -407,7 +525,10 @@ static int parquetFilter(
   sqlite3_value **argv
 ){
   try {
-    ParquetCursor* cursor = ((sqlite3_vtab_cursor_parquet*)cur)->cursor;
+    sqlite3_vtab_cursor_parquet* vtab_cursor_parquet = (sqlite3_vtab_cursor_parquet*)cur;
+    sqlite3_vtab_parquet* vtab_parquet = (sqlite3_vtab_parquet*)(vtab_cursor_parquet->base.pVtab);
+    sqlite3* db = vtab_parquet->db;
+    ParquetCursor* cursor = vtab_cursor_parquet->cursor;
     sqlite3_index_info* indexInfo = (sqlite3_index_info*)idxStr;
 
 #ifdef DEBUG
@@ -451,13 +572,40 @@ static int parquetFilter(
         type = Null;
       }
 
-      Constraint constraint(
+      std::string columnName = "rowid";
+      if(indexInfo->aConstraint[i].iColumn >= 0) {
+        columnName = cursor->getTable()->columnName(indexInfo->aConstraint[i].iColumn);
+      }
+
+      RowGroupBitmap bitmap = RowGroupBitmap(cursor->getNumRowGroups());
+      Constraint dummy(
+        bitmap,
         indexInfo->aConstraint[i].iColumn,
+        columnName,
         constraintOperatorFromSqlite(indexInfo->aConstraint[i].op),
         type,
         intValue,
         doubleValue,
         blobValue);
+
+      std::vector<unsigned char> actual = getRowGroupsForClause(db, cursor->getTable()->getTableName(), dummy.describe());
+      if(actual.size() > 0) {
+        // Initialize the estimate to be the actual -- eventually they'll converge
+        // and we'll stop writing back to the db.
+        std::vector<unsigned char> estimate = actual;
+        bitmap = RowGroupBitmap(estimate, actual);
+      }
+
+      Constraint constraint(
+        bitmap,
+        indexInfo->aConstraint[i].iColumn,
+        columnName,
+        constraintOperatorFromSqlite(indexInfo->aConstraint[i].op),
+        type,
+        intValue,
+        doubleValue,
+        blobValue);
+
       constraints.push_back(constraint);
       j++;
     }
@@ -555,7 +703,7 @@ static sqlite3_module ParquetModule = {
   parquetConnect,           /* xConnect */
   parquetBestIndex,         /* xBestIndex */
   parquetDisconnect,        /* xDisconnect */
-  parquetDisconnect,        /* xDestroy */
+  parquetDestroy,           /* xDestroy */
   parquetOpen,              /* xOpen - open a cursor */
   parquetClose,             /* xClose - close a cursor */
   parquetFilter,            /* xFilter - configure scan constraints */

parquet/parquet_cursor.cc

@@ -1,7 +1,6 @@
 #include "parquet_cursor.h"
 
-ParquetCursor::ParquetCursor(ParquetTable* table) {
+ParquetCursor::ParquetCursor(ParquetTable* table): table(table) {
-  this->table = table;
   reader = NULL;
   reset(std::vector<Constraint>());
 }
@@ -518,6 +517,7 @@ bool ParquetCursor::currentRowSatisfiesDoubleFilter(Constraint& constraint) {
 // This avoids opening rowgroups that can't return useful
 // data, which provides substantial performance benefits.
 bool ParquetCursor::currentRowGroupSatisfiesFilter() {
+  bool overallRv = true;
   for(unsigned int i = 0; i < constraints.size(); i++) {
     int column = constraints[i].column;
     int op = constraints[i].op;
@@ -527,9 +527,7 @@ bool ParquetCursor::currentRowGroupSatisfiesFilter() {
       rv = currentRowGroupSatisfiesRowIdFilter(constraints[i]);
     } else {
       std::unique_ptr<parquet::ColumnChunkMetaData> md = rowGroupMetadata->ColumnChunk(column);
-      if(!md->is_stats_set()) {
+      if(md->is_stats_set()) {
-        continue;
-      }
         std::shared_ptr<parquet::RowGroupStatistics> stats = md->statistics();
 
         // SQLite is much looser with types than you might expect if you
@@ -562,12 +560,19 @@ bool ParquetCursor::currentRowGroupSatisfiesFilter() {
           }
         }
       }
-
-    if(!rv)
-      return false;
     }
 
-  return true;
+    // and it with the existing actual, which may have come from a previous run
+    rv = rv && constraints[i].bitmap.getActualMembership(rowGroupId);
+    if(!rv) {
+      constraints[i].bitmap.setEstimatedMembership(rowGroupId, rv);
+      constraints[i].bitmap.setActualMembership(rowGroupId, rv);
+    }
+    overallRv = overallRv && rv;
+  }
+
+//  printf("rowGroup %d %s\n", rowGroupId, overallRv ? "may satisfy" : "does not satisfy");
+  return overallRv;
 }
 
 
@@ -609,9 +614,22 @@ start:
   // Increment rowId so currentRowGroupSatisfiesRowIdFilter can access it;
   // it'll get decremented by our caller
   rowId++;
+
+  // We're going to scan this row group; reset the expectation of discovering
+  // a row
+  for(unsigned int i = 0; i < constraints.size(); i++) {
+    if(rowGroupId > 0 && constraints[i].rowGroupId == rowGroupId - 1) {
+      constraints[i].bitmap.setActualMembership(rowGroupId - 1, constraints[i].hadRows);
+    }
+    constraints[i].hadRows = false;
+  }
+
   if(!currentRowGroupSatisfiesFilter())
     goto start;
 
+  for(unsigned int i = 0; i < constraints.size(); i++) {
+    constraints[i].rowGroupId = rowGroupId;
+  }
   return true;
 }
 
@@ -623,6 +641,7 @@ start:
 // and the extension, which can add up on a dataset of tens
 // of millions of rows.
 bool ParquetCursor::currentRowSatisfiesFilter() {
+  bool overallRv = true;
   for(unsigned int i = 0; i < constraints.size(); i++) {
     bool rv = true;
     int column = constraints[i].column;
@@ -648,13 +667,18 @@ bool ParquetCursor::currentRowSatisfiesFilter() {
       }
     }
 
-    if(!rv)
+    // it defaults to false; so only set it if true
-      return false;
+    // ideally we'd short-circuit if we'd already set this group as visited
+    if(rv) {
+      constraints[i].hadRows = true;
     }
-  return true;
+    overallRv = overallRv && rv;
+  }
+  return overallRv;
 }
 
 void ParquetCursor::next() {
+  // Returns true if we've crossed a row group boundary
 start:
   if(rowsLeftInRowGroup == 0) {
     if(!nextRowGroup()) {
@@ -672,7 +696,6 @@ start:
   rowId++;
   if(!currentRowSatisfiesFilter())
     goto start;
-
 }
 
 int ParquetCursor::getRowId() {
@@ -939,7 +962,7 @@ void ParquetCursor::reset(std::vector<Constraint> constraints) {
   // TODO: consider having a long lived handle in ParquetTable that can be borrowed
   // without incurring the cost of opening the file from scratch twice
   reader = parquet::ParquetFileReader::OpenFile(
-      table->file.data(),
+      table->getFile().data(),
       true,
       parquet::default_reader_properties(),
       table->getMetadata());
@@ -955,4 +978,10 @@ void ParquetCursor::reset(std::vector<Constraint> constraints) {
   numRowGroups = reader->metadata()->num_row_groups();
 }
 
-ParquetTable* ParquetCursor::getTable() { return table; }
+ParquetTable* ParquetCursor::getTable() const { return table; }
+
+unsigned int ParquetCursor::getNumRowGroups() const { return numRowGroups; }
+unsigned int ParquetCursor::getNumConstraints() const { return constraints.size(); }
+const Constraint& ParquetCursor::getConstraint(unsigned int i) const { return constraints[i]; }
+
+

parquet/parquet_cursor.h

@@ -56,9 +56,12 @@ public:
 
   void ensureColumn(int col);
   bool isNull(int col);
+  unsigned int getNumRowGroups() const;
+  unsigned int getNumConstraints() const;
+  const Constraint& getConstraint(unsigned int i) const;
   parquet::Type::type getPhysicalType(int col);
   parquet::LogicalType::type getLogicalType(int col);
-  ParquetTable* getTable();
+  ParquetTable* getTable() const;
 
   int getInt32(int col);
   long getInt64(int col);

parquet/parquet_filter.cc

@@ -1,19 +1,25 @@
 #include "parquet_filter.h"
 
 Constraint::Constraint(
+  RowGroupBitmap bitmap,
   int column,
+  std::string columnName,
   ConstraintOperator op,
   ValueType type,
   int64_t intValue,
   double doubleValue,
   std::vector<unsigned char> blobValue
-) {
+): bitmap(bitmap),
-  this->column = column;
+   column(column),
-  this->op = op;
+   columnName(columnName),
-  this->type = type;
+   op(op),
-  this->intValue = intValue;
+   type(type),
-  this->doubleValue = doubleValue;
+   intValue(intValue),
-  this->blobValue = blobValue;
+   doubleValue(doubleValue),
+   blobValue(blobValue),
+   hadRows(false) {
+     RowGroupBitmap bm = bitmap;
+     this->bitmap = bm;
 
   if(type == Text) {
     stringValue = std::string((char*)&blobValue[0], blobValue.size());
@@ -34,3 +40,72 @@ Constraint::Constraint(
     }
   }
 }
+
+std::string Constraint::describe() const {
+  std::string rv;
+  rv.append(columnName);
+  rv.append(" ");
+  switch(op) {
+    case Equal:
+      rv.append("=");
+      break;
+    case GreaterThan:
+      rv.append(">");
+      break;
+    case LessThanOrEqual:
+      rv.append("<=");
+      break;
+    case LessThan:
+      rv.append("<");
+      break;
+    case GreaterThanOrEqual:
+      rv.append(">=");
+      break;
+    case Match:
+      rv.append("MATCH");
+      break;
+    case Like:
+      rv.append("LIKE");
+      break;
+    case Glob:
+      rv.append("GLOB");
+      break;
+    case Regexp:
+      rv.append("REGEXP");
+      break;
+    case NotEqual:
+      rv.append("<>");
+      break;
+    case IsNot:
+      rv.append("IS NOT");
+      break;
+    case IsNotNull:
+      rv.append("IS NOT NULL");
+      break;
+    case IsNull:
+      rv.append("IS NULL");
+      break;
+    case Is:
+      rv.append("IS");
+      break;
+  }
+  rv.append(" ");
+
+  switch(type) {
+    case Null:
+      rv.append("NULL");
+      break;
+    case Integer:
+      rv.append(std::to_string(intValue));
+      break;
+    case Double:
+      rv.append(std::to_string(doubleValue));
+      break;
+    case Blob:
+      break;
+    case Text:
+      rv.append(stringValue);
+      break;
+  }
+  return rv;
+}

parquet/parquet_filter.h

@@ -30,11 +30,63 @@ enum ValueType {
   Text
 };
 
+class RowGroupBitmap {
+  void setBit(std::vector<unsigned char>& membership, unsigned int rowGroup, bool isSet) {
+    int byte = rowGroup / 8;
+    int offset = rowGroup % 8;
+    unsigned char c = membership[byte];
+    c &= ~(1UL << offset);
+    if(isSet) {
+      c |= 1UL << offset;
+    }
+    membership[byte] = c;
+  }
+// Compares estimated rowGroupFilter results against observed results
+// when we explored the row group. This lets us cache 
+public:
+  RowGroupBitmap(unsigned int totalRowGroups) {
+    // Initialize everything to assume that all row groups match.
+    // As we discover otherwise, we'll update that assumption.
+    for(unsigned int i = 0; i < (totalRowGroups + 7) / 8; i++) {
+      estimatedMembership.push_back(0xFF);
+      actualMembership.push_back(0xFF);
+    }
+  }
+
+  RowGroupBitmap(
+      std::vector<unsigned char> estimatedMembership,
+      std::vector<unsigned char> actualMembership) :
+    estimatedMembership(estimatedMembership),
+    actualMembership(actualMembership) {
+  }
+
+  std::vector<unsigned char> estimatedMembership;
+  std::vector<unsigned char> actualMembership;
+  // Pass false only if definitely does not have rows
+  void setEstimatedMembership(unsigned int rowGroup, bool hasRows) {
+    setBit(estimatedMembership, rowGroup, hasRows);
+  }
+
+  // Pass false only after exhausting all rows
+  void setActualMembership(unsigned int rowGroup, bool hadRows) {
+    setBit(actualMembership, rowGroup, hadRows);
+  }
+
+  bool getActualMembership(unsigned int rowGroup) {
+    int byte = rowGroup / 8;
+    int offset = rowGroup % 8;
+
+    return (actualMembership[byte] >> offset) & 1U;
+  }
+};
+
 class Constraint {
 public:
   // Kind of a messy constructor function, but it's just for internal use, so whatever.
   Constraint(
+    RowGroupBitmap bitmap,
     int column,
+    std::string columnName,
     ConstraintOperator op,
     ValueType type,
     int64_t intValue,
@@ -42,7 +94,9 @@ public:
     std::vector<unsigned char> blobValue
   );
 
+  RowGroupBitmap bitmap;
   int column; // underlying column in the query
+  std::string columnName;
   ConstraintOperator op;
   ValueType type;
 
@@ -54,6 +108,15 @@ public:
 
   // Only set when stringValue is set and op == Like
   std::string likeStringValue;
+
+  // A unique identifier for this constraint, e.g.
+  // col0 = 'Dawson Creek'
+  std::string describe() const;
+
+  // This is a temp field used while evaluating if a rowgroup had rows
+  // that matched this constraint.
+  int rowGroupId;
+  bool hadRows;
 };
 
 #endif

parquet/parquet_table.cc

@@ -2,9 +2,7 @@
 
 #include "parquet/api/reader.h"
 
-ParquetTable::ParquetTable(std::string file) {
+ParquetTable::ParquetTable(std::string file, std::string tableName): file(file), tableName(tableName) {
-  this->file = file;
-
   std::unique_ptr<parquet::ParquetFileReader> reader = parquet::ParquetFileReader::OpenFile(file.data());
   metadata = reader->metadata();
 }
@@ -138,3 +136,6 @@ std::string ParquetTable::CreateStatement() {
 }
 
 std::shared_ptr<parquet::FileMetaData> ParquetTable::getMetadata() { return metadata; }
+
+const std::string& ParquetTable::getFile() { return file; }
+const std::string& ParquetTable::getTableName() { return tableName; }

parquet/parquet_table.h

@@ -6,16 +6,19 @@
 #include "parquet/api/reader.h"
 
 class ParquetTable {
+  std::string file;
+  std::string tableName;
   std::vector<std::string> columnNames;
   std::shared_ptr<parquet::FileMetaData> metadata;
 
 
 public:
-  ParquetTable(std::string file);
+  ParquetTable(std::string file, std::string tableName);
   std::string CreateStatement();
-  std::string file;
   std::string columnName(int idx);
   std::shared_ptr<parquet::FileMetaData> getMetadata();
+  const std::string& getFile();
+  const std::string& getTableName();
 };
 
 #endif

tests/test-queries

@@ -47,7 +47,7 @@ main() {
   fi
 
   cat "$root"/parquet-generator/*.sql > "$root"/testcase-bootstrap.sql
-  rm test.db
+  rm -f test.db
   "$root"/sqlite/sqlite3 test.db -init "$root"/testcase-bootstrap.sql < /dev/null
   if [ ! -v NO_DEBUG ] && [ "$(cat testcases.txt | wc -l)" == "1" ]; then
     set -x