Add new feature: SHOW DATABASES LIKE

src/Interpreters/InterpreterShowTablesQuery.cpp

@@ -31,7 +31,21 @@ String InterpreterShowTablesQuery::getRewrittenQuery()
 
     /// SHOW DATABASES
     if (query.databases)
-        return "SELECT name FROM system.databases";
+    {
+        std::stringstream rewritten_query;
+        rewritten_query << "SELECT name FROM system.databases";
+
+        if (!query.like.empty())
+        {
+            rewritten_query << " WHERE name " << (query.not_like ? "NOT " : "") << "LIKE " << std::quoted(query.like, '\'');
+        }
+
+        if (query.limit_length)
+            rewritten_query << " LIMIT " << query.limit_length;
+
+        DUMP(rewritten_query.str());
+        return rewritten_query.str();
+    }
 
     /// SHOW CLUSTER/CLUSTERS 
     if (query.clusters)

src/Parsers/ASTShowTablesQuery.cpp

@@ -18,6 +18,20 @@ void ASTShowTablesQuery::formatQueryImpl(const FormatSettings & settings, Format
     if (databases)
     {
         settings.ostr << (settings.hilite ? hilite_keyword : "") << "SHOW DATABASES" << (settings.hilite ? hilite_none : "");
+
+        if (!like.empty())
+            settings.ostr
+                << (settings.hilite ? hilite_keyword : "")
+                << (not_like ? " NOT" : "")
+                << (case_insensitive_like ? " ILIKE " : " LIKE ")
+                << (settings.hilite ? hilite_none : "")
+                << std::quoted(like, '\'');
+
+        if (limit_length)
+        {
+            settings.ostr << (settings.hilite ? hilite_keyword : "") << " LIMIT " << (settings.hilite ? hilite_none : "");
+            limit_length->formatImpl(settings, state, frame);
+        }
     }
     else if (clusters)
     {

src/Parsers/ParserShowTablesQuery.cpp

@@ -46,6 +46,25 @@ bool ParserShowTablesQuery::parseImpl(Pos & pos, ASTPtr & node, Expected & expec
     if (s_databases.ignore(pos))
     {
         query->databases = true;
+
+        if (s_not.ignore(pos, expected))
+            query->not_like = true;
+
+        if (bool insensitive = s_ilike.ignore(pos, expected); insensitive || s_like.ignore(pos, expected))
+        {
+            if (insensitive)
+                query->case_insensitive_like = true;
+
+            if (!like_p.parse(pos, like, expected))
+                return false;
+        }
+        else if (query->not_like)
+            return false;
+        if (s_limit.ignore(pos, expected))
+        {
+            if (!exp_elem.parse(pos, query->limit_length, expected))
+                return false;
+        }
     }
     else if (s_clusters.ignore(pos))
     {

tests/queries/0_stateless/01470_show_databases_like.reference

@@ -0,0 +1 @@
+test_01470

tests/queries/0_stateless/01470_show_databases_like.sql

@@ -0,0 +1,3 @@
+create database if not exists test_01470;
+show databases like '%01470';
+drop database test_01470;