Merge pull request #54337 from wat-ze-hex/show-functions-2023-09-04

Add SHOW FUNCTIONS support to client

docs/en/sql-reference/statements/show.md

@@ -638,3 +638,16 @@ Outputs the content of the [system.table_engines](../../operations/system-tables
 **See Also**
 
 - [system.table_engines](../../operations/system-tables/table_engines.md) table
+
+## SHOW FUNCTIONS
+
+``` sql
+SHOW FUNCTIONS [LIKE | ILIKE '<pattern>']
+```
+
+Outputs the content of the [system.functions](../../operations/system-tables/functions.md) table.
+
+If either `LIKE` or `ILIKE` clause is specified, the query returns a list of system functions whose names match the provided `<pattern>`.
+
+**See Also**
+- [system.functions](../../operations/system-tables/functions.md) table

src/Interpreters/InterpreterFactory.cpp

@@ -19,6 +19,7 @@
 #include <Parsers/ASTSelectWithUnionQuery.h>
 #include <Parsers/ASTSetQuery.h>
 #include <Parsers/ASTShowEngineQuery.h>
+#include <Parsers/ASTShowFunctionsQuery.h>
 #include <Parsers/ASTShowProcesslistQuery.h>
 #include <Parsers/ASTShowTablesQuery.h>
 #include <Parsers/ASTShowColumnsQuery.h>
@@ -80,6 +81,7 @@
 #include <Interpreters/InterpreterSetQuery.h>
 #include <Interpreters/InterpreterShowCreateQuery.h>
 #include <Interpreters/InterpreterShowEngineQuery.h>
+#include <Interpreters/InterpreterShowFunctionsQuery.h>
 #include <Interpreters/InterpreterShowProcesslistQuery.h>
 #include <Interpreters/InterpreterShowTablesQuery.h>
 #include <Interpreters/InterpreterShowColumnsQuery.h>
@@ -203,6 +205,10 @@ std::unique_ptr<IInterpreter> InterpreterFactory::get(ASTPtr & query, ContextMut
     {
         return std::make_unique<InterpreterShowEnginesQuery>(query, context);
     }
+    else if (query->as<ASTShowFunctionsQuery>())
+    {
+        return std::make_unique<InterpreterShowFunctionsQuery>(query, context);
+    }
     else if (query->as<ASTUseQuery>())
     {
         return std::make_unique<InterpreterUseQuery>(query, context);

src/Interpreters/InterpreterShowFunctionsQuery.cpp

@@ -0,0 +1,46 @@
+#include <Interpreters/InterpreterShowFunctionsQuery.h>
+
+#include <Interpreters/Context.h>
+#include <Interpreters/DatabaseCatalog.h>
+#include <Interpreters/executeQuery.h>
+#include <Parsers/ASTShowFunctionsQuery.h>
+
+namespace DB
+{
+
+InterpreterShowFunctionsQuery::InterpreterShowFunctionsQuery(const ASTPtr & query_ptr_, ContextMutablePtr context_)
+    : WithMutableContext(context_), query_ptr(query_ptr_)
+{
+}
+
+BlockIO InterpreterShowFunctionsQuery::execute()
+{
+    return executeQuery(getRewrittenQuery(), getContext(), true);
+}
+
+String InterpreterShowFunctionsQuery::getRewrittenQuery()
+{
+    constexpr const char * functions_table = "functions";
+
+    const auto & query = query_ptr->as<ASTShowFunctionsQuery &>();
+
+    DatabasePtr systemDb = DatabaseCatalog::instance().getSystemDatabase();
+
+    String rewritten_query = fmt::format(
+        R"(
+SELECT *
+FROM {}.{})",
+        systemDb->getDatabaseName(),
+        functions_table);
+
+    if (!query.like.empty())
+    {
+        rewritten_query += " WHERE name ";
+        rewritten_query += query.case_insensitive_like ? "ILIKE " : "LIKE ";
+        rewritten_query += fmt::format("'{}'", query.like);
+    }
+
+    return rewritten_query;
+}
+
+}

src/Interpreters/InterpreterShowFunctionsQuery.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
+
+namespace DB
+{
+
+class Context;
+
+class InterpreterShowFunctionsQuery : public IInterpreter, WithMutableContext
+{
+public:
+    InterpreterShowFunctionsQuery(const ASTPtr & query_ptr_, ContextMutablePtr context_);
+
+    BlockIO execute() override;
+
+    bool ignoreQuota() const override { return true; }
+    bool ignoreLimits() const override { return true; }
+
+private:
+    ASTPtr query_ptr;
+
+    String getRewrittenQuery();
+};
+
+}

src/Parsers/ASTShowFunctionsQuery.cpp

@@ -0,0 +1,25 @@
+#include <Parsers/ASTShowFunctionsQuery.h>
+
+#include <Common/quoteString.h>
+
+namespace DB
+{
+
+ASTPtr ASTShowFunctionsQuery::clone() const
+{
+    auto res = std::make_shared<ASTShowFunctionsQuery>(*this);
+    res->children.clear();
+    cloneOutputOptions(*res);
+    return res;
+}
+
+void ASTShowFunctionsQuery::formatQueryImpl(const FormatSettings & settings, FormatState &, FormatStateStacked) const
+{
+    settings.ostr << (settings.hilite ? hilite_keyword : "") << "SHOW FUNCTIONS" << (settings.hilite ? hilite_none : "");
+
+    if (!like.empty())
+        settings.ostr << (settings.hilite ? hilite_keyword : "") << (case_insensitive_like ? " ILIKE " : " LIKE ")
+                      << (settings.hilite ? hilite_none : "") << DB::quote << like;
+}
+
+}

src/Parsers/ASTShowFunctionsQuery.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <Parsers/ASTQueryWithOutput.h>
+#include <Parsers/IAST_fwd.h>
+
+namespace DB
+{
+
+class ASTShowFunctionsQuery : public ASTQueryWithOutput
+{
+public:
+    bool case_insensitive_like = false;
+    String like;
+
+    String getID(char) const override { return "ShowFunctions"; }
+    ASTPtr clone() const override;
+    QueryKind getQueryKind() const override { return QueryKind::Show; }
+
+protected:
+    void formatQueryImpl(const FormatSettings & settings, FormatState &, FormatStateStacked) const override;
+};
+
+}

src/Parsers/ParserQueryWithOutput.cpp

@@ -18,6 +18,7 @@
 #include <Parsers/ParserShowTablesQuery.h>
 #include <Parsers/ParserShowColumnsQuery.h>
 #include <Parsers/ParserShowEngineQuery.h>
+#include <Parsers/ParserShowFunctionsQuery.h>
 #include <Parsers/ParserShowIndexesQuery.h>
 #include <Parsers/ParserTablePropertiesQuery.h>
 #include <Parsers/ParserWatchQuery.h>
@@ -40,6 +41,7 @@ bool ParserQueryWithOutput::parseImpl(Pos & pos, ASTPtr & node, Expected & expec
     ParserShowTablesQuery show_tables_p;
     ParserShowColumnsQuery show_columns_p;
     ParserShowEnginesQuery show_engine_p;
+    ParserShowFunctionsQuery show_functions_p;
     ParserShowIndexesQuery show_indexes_p;
     ParserSelectWithUnionQuery select_p;
     ParserTablePropertiesQuery table_p;
@@ -71,6 +73,7 @@ bool ParserQueryWithOutput::parseImpl(Pos & pos, ASTPtr & node, Expected & expec
         || show_tables_p.parse(pos, query, expected)
         || show_columns_p.parse(pos, query, expected)
         || show_engine_p.parse(pos, query, expected)
+        || show_functions_p.parse(pos, query, expected)
         || show_indexes_p.parse(pos, query, expected)
         || table_p.parse(pos, query, expected)
         || describe_cache_p.parse(pos, query, expected)

src/Parsers/ParserShowFunctionsQuery.cpp

@@ -0,0 +1,35 @@
+#include <Parsers/ParserShowFunctionsQuery.h>
+
+#include <Parsers/ASTLiteral.h>
+#include <Parsers/ASTShowFunctionsQuery.h>
+#include <Parsers/CommonParsers.h>
+#include <Parsers/ExpressionElementParsers.h>
+
+namespace DB
+{
+
+bool ParserShowFunctionsQuery::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
+{
+    ASTPtr like;
+
+    auto query = std::make_shared<ASTShowFunctionsQuery>();
+    if (!ParserKeyword("SHOW FUNCTIONS").ignore(pos, expected))
+        return false;
+
+    if (bool insensitive = ParserKeyword("ILIKE").ignore(pos, expected); insensitive || ParserKeyword("LIKE").ignore(pos, expected))
+    {
+        if (insensitive)
+            query->case_insensitive_like = true;
+
+        if (!ParserStringLiteral().parse(pos, like, expected))
+            return false;
+    }
+
+    if (like)
+        query->like = like->as<ASTLiteral &>().value.safeGet<const String &>();
+    node = query;
+
+    return true;
+}
+
+}

src/Parsers/ParserShowFunctionsQuery.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <Parsers/IParserBase.h>
+
+namespace DB
+{
+
+/** Parses queries of the form
+ * SHOW FUNCTIONS [LIKE | ILIKE '<pattern>']
+ */
+class ParserShowFunctionsQuery : public IParserBase
+{
+protected:
+    const char * getName() const override { return "SHOW FUNCTIONS query"; }
+
+    bool parseImpl(Pos & pos, ASTPtr & node, Expected & expected) override;
+};
+
+}

tests/queries/0_stateless/00419_show_sql_queries.sh

@@ -8,3 +8,4 @@ $CLICKHOUSE_CLIENT -q "SHOW PROCESSLIST" &>/dev/null
 $CLICKHOUSE_CLIENT -q "SHOW DATABASES" &>/dev/null
 $CLICKHOUSE_CLIENT -q "SHOW TABLES" &>/dev/null
 $CLICKHOUSE_CLIENT -q "SHOW ENGINES" &>/dev/null
+$CLICKHOUSE_CLIENT -q "SHOW FUNCTIONS" &>/dev/null

tests/queries/0_stateless/02875_show_functions.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+
+CURDIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+# shellcheck source=../shell_config.sh
+. "$CURDIR"/../shell_config.sh
+
+diff -q <($CLICKHOUSE_CLIENT -q "SELECT * from system.functions") \
+        <($CLICKHOUSE_CLIENT -q "SHOW FUNCTIONS")
+
+diff -q <($CLICKHOUSE_CLIENT -q "SELECT * FROM system.functions WHERE name ILIKE 'quantile%'") \
+        <($CLICKHOUSE_CLIENT -q "SHOW FUNCTIONS ILIKE 'quantile%'")
+
+diff -q <($CLICKHOUSE_CLIENT -q "SELECT * FROM system.functions WHERE name LIKE 'median%'") \
+	<($CLICKHOUSE_CLIENT -q "SHOW FUNCTIONS LIKE 'median%'")