From 6a1d1f55080dcf53c72501831d7c00e3710e8fa7 Mon Sep 17 00:00:00 2001
From: Danila Kutenin <kutdanila@yandex.ru>
Date: Mon, 11 Feb 2019 15:42:20 +0300
Subject: [PATCH] Better hints provider

---
 dbms/src/Common/IFactoryWithAliases.h           |  5 +++--
 dbms/src/Common/NamePrompter.h                  | 17 +++++++++++++----
 .../00834_hints_for_type_function_typos.sh      | 10 +++++++++-
 3 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/dbms/src/Common/IFactoryWithAliases.h b/dbms/src/Common/IFactoryWithAliases.h
index db0b4e37864..f7b930f57c3 100644
--- a/dbms/src/Common/IFactoryWithAliases.h
+++ b/dbms/src/Common/IFactoryWithAliases.h
@@ -130,9 +130,10 @@ private:
 
     /**
       * prompter for names, if a person makes a typo for some function or type, it
-      * helps to find best possible match (in particular, edit distance is one or two symbols)
+      * helps to find best possible match (in particular, edit distance is done like in clang
+      * (max edit distance is (typo.size() + 2) / 3 and not bigger than)
       */
-    NamePrompter</*MistakeFactor=*/2, /*MaxNumHints=*/2> prompter;
+    NamePrompter</*MaxNumHints=*/2> prompter;
 };
 
 }
diff --git a/dbms/src/Common/NamePrompter.h b/dbms/src/Common/NamePrompter.h
index 21f35a7b9fe..40460c971d0 100644
--- a/dbms/src/Common/NamePrompter.h
+++ b/dbms/src/Common/NamePrompter.h
@@ -4,12 +4,13 @@
 
 #include <algorithm>
 #include <cctype>
+#include <cmath>
 #include <queue>
 #include <utility>
 
 namespace DB
 {
-template <size_t MistakeFactor, size_t MaxNumHints>
+template <size_t MaxNumHints>
 class NamePrompter
 {
 public:
@@ -53,10 +54,18 @@ private:
 
     static void appendToQueue(size_t ind, const String & name, DistanceIndexQueue & queue, const std::vector<String> & prompting_strings)
     {
-        if (prompting_strings[ind].size() <= name.size() + MistakeFactor && prompting_strings[ind].size() + MistakeFactor >= name.size())
+        const String & prompt = prompting_strings[ind];
+
+        /// Clang SimpleTypoCorrector logic
+        const size_t min_possible_edit_distance = std::abs(static_cast<int64_t>(name.size()) - static_cast<int64_t>(prompt.size()));
+        const size_t mistake_factor = (name.size() + 2) / 3;
+        if (min_possible_edit_distance > 0 && name.size() / min_possible_edit_distance < 3)
+            return;
+
+        if (prompt.size() <= name.size() + mistake_factor && prompt.size() + mistake_factor >= name.size())
         {
-            size_t distance = levenshteinDistance(prompting_strings[ind], name);
-            if (distance <= MistakeFactor)
+            size_t distance = levenshteinDistance(prompt, name);
+            if (distance <= mistake_factor)
             {
                 queue.emplace(distance, ind);
                 if (queue.size() > MaxNumHints)
diff --git a/dbms/tests/queries/0_stateless/00834_hints_for_type_function_typos.sh b/dbms/tests/queries/0_stateless/00834_hints_for_type_function_typos.sh
index 8650cc2d56b..0352002d160 100755
--- a/dbms/tests/queries/0_stateless/00834_hints_for_type_function_typos.sh
+++ b/dbms/tests/queries/0_stateless/00834_hints_for_type_function_typos.sh
@@ -11,4 +11,12 @@ $CLICKHOUSE_CLIENT -q "select positin(*) from system.functions;" 2>&1 | grep "Ma
 $CLICKHOUSE_CLIENT -q "select POSITIO(*) from system.functions;" 2>&1 | grep "Maybe you meant: \['position'" &>/dev/null;
 $CLICKHOUSE_CLIENT -q "select fount(*) from system.functions;" 2>&1 | grep "Maybe you meant: \['count'" | grep "Maybe you meant: \['round'" | grep "Or unknown aggregate function" &>/dev/null;
 $CLICKHOUSE_CLIENT -q "select positin(*) from system.functions;" 2>&1 | grep -v "Or unknown aggregate function" &>/dev/null;
-$CLICKHOUSE_CLIENT -q "select pov(*) from system.functions;" 2>&1 | grep "Maybe you meant: \['pow','cos'\]" &>/dev/null;
+$CLICKHOUSE_CLIENT -q "select pov(*) from system.functions;" 2>&1 | grep "Maybe you meant: \['pow'\]" &>/dev/null;
+$CLICKHOUSE_CLIENT -q "select getColumnStructure('abc');" 2>&1 | grep "Maybe you meant: \['dumpColumnStructure'\]" &>/dev/null;
+$CLICKHOUSE_CLIENT -q "select gutColumnStructure('abc');" 2>&1 | grep "Maybe you meant: \['dumpColumnStructure'\]" &>/dev/null;
+$CLICKHOUSE_CLIENT -q "select gupColumnStructure('abc');" 2>&1 | grep "Maybe you meant: \['dumpColumnStructure'\]" &>/dev/null;
+$CLICKHOUSE_CLIENT -q "select provideColumnStructure('abc');" 2>&1 | grep "Maybe you meant: \['dumpColumnStructure'\]" &>/dev/null;
+$CLICKHOUSE_CLIENT -q "select multiposicionutf7('abc');" 2>&1 | grep "Maybe you meant: \['multiPositionUTF8','multiPosition'\]" &>/dev/null;
+$CLICKHOUSE_CLIENT -q "select multiposicionutf7casesensitive('abc');" 2>&1 | grep "Maybe you meant: \['multiPositionCaseInsensitive'\]" &>/dev/null;
+$CLICKHOUSE_CLIENT -q "select multiposicionutf7sensitive('abc');" 2>&1 | grep "Maybe you meant: \['multiPositionCaseInsensitive'\]" &>/dev/null;
+$CLICKHOUSE_CLIENT -q "select multiPosicionSensitiveUTF8('abc');" 2>&1 | grep "Maybe you meant: \['multiPositionCaseInsensitiveUTF8'\]" &>/dev/null;