ClickHouse/src/Parsers/IAST.h

#pragma once

#include <base/types.h>
#include <Parsers/IAST_fwd.h>
#include <Parsers/IdentifierQuotingStyle.h>
#include <Parsers/LiteralEscapingStyle.h>
#include <Common/Exception.h>
#include <Common/TypePromotion.h>
#include <IO/WriteBufferFromString.h>

#include <algorithm>
#include <set>
#include <list>


class SipHash;


namespace DB
{

namespace ErrorCodes
{
    extern const int LOGICAL_ERROR;
}

using IdentifierNameSet = std::set<String>;

class WriteBuffer;
using Strings = std::vector<String>;

/** Element of the syntax tree (hereinafter - directed acyclic graph with elements of semantics)
  */
class IAST : public std::enable_shared_from_this<IAST>, public TypePromotion<IAST>
{
public:
    ASTs children;

    virtual ~IAST();
    IAST() = default;
    IAST(const IAST &) = default;
    IAST & operator=(const IAST &) = default;

    /** Get the canonical name of the column if the element is a column */
    String getColumnName() const;

    /** Same as the above but ensure no alias names are used. This is for index analysis */
    String getColumnNameWithoutAlias() const;

    virtual void appendColumnName(WriteBuffer &) const
    {
        throw Exception(ErrorCodes::LOGICAL_ERROR, "Trying to get name of not a column: {}", getID());
    }

    virtual void appendColumnNameWithoutAlias(WriteBuffer &) const
    {
        throw Exception(ErrorCodes::LOGICAL_ERROR, "Trying to get name of not a column: {}", getID());
    }

    /** Get the alias, if any, or the canonical name of the column, if it is not. */
    virtual String getAliasOrColumnName() const { return getColumnName(); }

    /** Get the alias, if any, or an empty string if it does not exist, or if the element does not support aliases. */
    virtual String tryGetAlias() const { return String(); }

    /** Set the alias. */
    virtual void setAlias(const String & /*to*/)
    {
        throw Exception(ErrorCodes::LOGICAL_ERROR, "Can't set alias of {}", getColumnName());
    }

    /** Get the text that identifies this element. */
    virtual String getID(char delimiter = '_') const = 0; /// NOLINT

    ASTPtr ptr() { return shared_from_this(); }

    /** Get a deep copy of the tree. Cloned object must have the same range. */
    virtual ASTPtr clone() const = 0;

    /** Get hash code, identifying this element and its subtree.
     *  Hashing by default ignores aliases (e.g. identifier aliases, function aliases, literal aliases) which is
     *  useful for common subexpression elimination. Set 'ignore_aliases = false' if you don't want that behavior.
      */
    using Hash = CityHash_v1_0_2::uint128;
    Hash getTreeHash(bool ignore_aliases) const;
    void updateTreeHash(SipHash & hash_state, bool ignore_aliases) const;
    virtual void updateTreeHashImpl(SipHash & hash_state, bool ignore_aliases) const;

    void dumpTree(WriteBuffer & ostr, size_t indent = 0) const;
    std::string dumpTree(size_t indent = 0) const;

    /** Check the depth of the tree.
      * If max_depth is specified and the depth is greater - throw an exception.
      * Returns the depth of the tree.
      */
    size_t checkDepth(size_t max_depth) const
    {
        return checkDepthImpl(max_depth);
    }

    /** Get total number of tree elements
     */
    size_t size() const;

    /** Same for the total number of tree elements.
      */
    size_t checkSize(size_t max_size) const;

    /** Get `set` from the names of the identifiers
     */
    virtual void collectIdentifierNames(IdentifierNameSet & set) const
    {
        for (const auto & child : children)
            child->collectIdentifierNames(set);
    }

    template <typename T>
    void set(T * & field, const ASTPtr & child)
    {
        if (!child)
            return;

        T * casted = dynamic_cast<T *>(child.get());
        if (!casted)
            throw Exception(ErrorCodes::LOGICAL_ERROR, "Could not cast AST subtree");

        children.push_back(child);
        field = casted;
    }

    template <typename T>
    void replace(T * & field, const ASTPtr & child)
    {
        if (!child)
            throw Exception(ErrorCodes::LOGICAL_ERROR, "Trying to replace AST subtree with nullptr");

        T * casted = dynamic_cast<T *>(child.get());
        if (!casted)
            throw Exception(ErrorCodes::LOGICAL_ERROR, "Could not cast AST subtree");

        for (ASTPtr & current_child : children)
        {
            if (current_child.get() == field)
            {
                current_child = child;
                field = casted;
                return;
            }
        }

        throw Exception(ErrorCodes::LOGICAL_ERROR, "AST subtree not found in children");
    }

    template <typename T>
    void setOrReplace(T * & field, const ASTPtr & child)
    {
        if (field)
            replace(field, child);
        else
            set(field, child);
    }

    template <typename T>
    void reset(T * & field)
    {
        if (field == nullptr)
            return;

        const auto child = std::find_if(children.begin(), children.end(), [field](const auto & p)
        {
           return p.get() == field;
        });

        if (child == children.end())
            throw Exception(ErrorCodes::LOGICAL_ERROR, "AST subtree not found in children");

        children.erase(child);
        field = nullptr;
    }

    /// After changing one of `children` elements, update the corresponding member pointer if needed.
    void updatePointerToChild(void * old_ptr, void * new_ptr)
    {
        forEachPointerToChild([old_ptr, new_ptr](void ** ptr) mutable
        {
            if (*ptr == old_ptr)
                *ptr = new_ptr;
        });
    }

    /// Convert to a string.

    /// Format settings.
    struct FormatSettings
    {
        WriteBuffer & ostr;
        bool one_line;
        bool hilite;
        bool always_quote_identifiers;
        IdentifierQuotingStyle identifier_quoting_style;
        bool show_secrets; /// Show secret parts of the AST (e.g. passwords, encryption keys).
        char nl_or_ws; /// Newline or whitespace.
        LiteralEscapingStyle literal_escaping_style;

        explicit FormatSettings(
            WriteBuffer & ostr_,
            bool one_line_,
            bool hilite_ = false,
            bool always_quote_identifiers_ = false,
            IdentifierQuotingStyle identifier_quoting_style_ = IdentifierQuotingStyle::Backticks,
            bool show_secrets_ = true,
            LiteralEscapingStyle literal_escaping_style_ = LiteralEscapingStyle::Regular)
            : ostr(ostr_)
            , one_line(one_line_)
            , hilite(hilite_)
            , always_quote_identifiers(always_quote_identifiers_)
            , identifier_quoting_style(identifier_quoting_style_)
            , show_secrets(show_secrets_)
            , nl_or_ws(one_line ? ' ' : '\n')
            , literal_escaping_style(literal_escaping_style_)
        {
        }

        FormatSettings(WriteBuffer & ostr_, const FormatSettings & other)
            : ostr(ostr_)
            , one_line(other.one_line)
            , hilite(other.hilite)
            , always_quote_identifiers(other.always_quote_identifiers)
            , identifier_quoting_style(other.identifier_quoting_style)
            , show_secrets(other.show_secrets)
            , nl_or_ws(other.nl_or_ws)
            , literal_escaping_style(other.literal_escaping_style)
        {
        }

        void writeIdentifier(const String & name) const;
    };

    /// State. For example, a set of nodes can be remembered, which we already walk through.
    struct FormatState
    {
        /** The SELECT query in which the alias was found; identifier of a node with such an alias.
          * It is necessary that when the node has met again, output only the alias.
          */
        std::set<std::tuple<
            const IAST * /* SELECT query node */,
            std::string /* alias */,
            Hash /* printed content */>> printed_asts_with_alias;
    };

    /// The state that is copied when each node is formatted. For example, nesting level.
    struct FormatStateStacked
    {
        UInt8 indent = 0;
        bool need_parens = false;
        bool expression_list_always_start_on_new_line = false;  /// Line feed and indent before expression list even if it's of single element.
        bool expression_list_prepend_whitespace = false; /// Prepend whitespace (if it is required)
        bool surround_each_list_element_with_parens = false;
        size_t list_element_index = 0;
        const IAST * current_select = nullptr;
    };

    void format(const FormatSettings & settings) const
    {
        FormatState state;
        formatImpl(settings, state, FormatStateStacked());
    }

    virtual void formatImpl(const FormatSettings & /*settings*/, FormatState & /*state*/, FormatStateStacked /*frame*/) const
    {
        throw Exception(ErrorCodes::LOGICAL_ERROR, "Unknown element in AST: {}", getID());
    }

    // Secrets are displayed regarding show_secrets, then SensitiveDataMasker is applied.
    // You can use Interpreters/formatWithPossiblyHidingSecrets.h for convenience.
    String formatWithPossiblyHidingSensitiveData(size_t max_length, bool one_line, bool show_secrets) const;

    /*
     * formatForLogging and formatForErrorMessage always hide secrets. This inconsistent
     * behaviour is due to the fact such functions are called from Client which knows nothing about
     * access rights and settings. Moreover, the only use case for displaying secrets are backups,
     * and backup tools use only direct input and ignore logs and error messages.
     */
    String formatForLogging(size_t max_length = 0) const
    {
        return formatWithPossiblyHidingSensitiveData(max_length, true, false);
    }

    String formatForErrorMessage() const
    {
        return formatWithPossiblyHidingSensitiveData(0, true, false);
    }

    virtual bool hasSecretParts() const { return childrenHaveSecretParts(); }

    void cloneChildren();

    enum class QueryKind : uint8_t
    {
        None = 0,
        Select,
        Insert,
        Delete,
        Create,
        Drop,
        Undrop,
        Rename,
        Optimize,
        Check,
        Alter,
        Grant,
        Revoke,
        Move,
        System,
        Set,
        Use,
        Show,
        Exists,
        Describe,
        Explain,
        Backup,
        Restore,
        KillQuery,
        ExternalDDL,
        Begin,
        Commit,
        Rollback,
        SetTransactionSnapshot,
        AsyncInsertFlush
    };
    /// Return QueryKind of this AST query.
    virtual QueryKind getQueryKind() const { return QueryKind::None; }

    /// For syntax highlighting.
    static const char * hilite_keyword;
    static const char * hilite_identifier;
    static const char * hilite_function;
    static const char * hilite_operator;
    static const char * hilite_alias;
    static const char * hilite_substitution;
    static const char * hilite_none;

protected:
    bool childrenHaveSecretParts() const;

    /// Some AST classes have naked pointers to children elements as members.
    /// This method allows to iterate over them.
    virtual void forEachPointerToChild(std::function<void(void**)>) {}

private:
    size_t checkDepthImpl(size_t max_depth) const;

    /** Forward linked list of ASTPtr to delete.
      * Used in IAST destructor to avoid possible stack overflow.
      */
    ASTPtr next_to_delete = nullptr;
    ASTPtr * next_to_delete_list_head = nullptr;
};

}