RelationalExpression *expr;

double selectivity;

// If this join is made using a hash join, estimates the width

// of each row as stored in the hash table, in bytes.

size_t estimated_bytes_per_row;

// The set of (additional) functional dependencies that are active

// after this join predicate has been applied. E.g. if we're joining

// on t1.x = t2.x, there will be a bit for that functional dependency.

// We don't currently support more complex join conditions, but there's

// no conceptual reason why we couldn't, e.g. a join on a = b + c

// could give rise to the FD {b, c} → a and possibly even {a, b} → c

// or {a, c} → b.

//

// Used in the processing of interesting orders.

FunctionalDependencySet functional_dependencies;

// A less compact form of functional_dependencies, used during building

// (FunctionalDependencySet bitmaps are only available after all functional

// indexes have been collected and Build() has been called).

Mem_root_array<int> functional_dependencies_idx;

// If this is a suitable semijoin: Contains the grouping given by the

// join key. If the rows are in this grouping, then the join optimizer will

// consider deduplicating on it and inverting the join. -1 otherwise.

int ordering_idx_needed_for_semijoin_rewrite = -1;

// Same as ordering_idx_needed_for_semijoin_rewrite, but given to the

// RemoveDuplicatesIterator for doing the actual grouping. Allocated

// on the MEM_ROOT. Can be empty, in which case a LIMIT 1 would do.

Item **semijoin_group = nullptr;

int semijoin_group_size = 0;

Item *condition;

// condition->used_tables(), converted to a NodeMap.

hypergraph::NodeMap used_nodes;

// tables referred to by the condition, plus any tables whose values

// can null any of those tables. (Even when reordering outer joins,

// at least one of those tables will still be present on the

// left-hand side of the outer join, so this is sufficient.)

//

// As a special case, we allow setting RAND_TABLE_BIT, even though it

// is normally part of a table_map, not a NodeMap.

hypergraph::NodeMap total_eligibility_set;

double selectivity;

// Whether this predicate is a join condition after all; it was promoted

// to a WHERE predicate since it was part of a cycle (see the comment in

// AddCycleEdges()). If it is, it is usually ignored so that we don't

// double-apply join conditions -- but if the join in question was not

// applied (because the cycle was broken at this point), the predicate

// would come into play. This is normally registered on the join itself

// (see RelationalExpression::join_predicate_bitmap), but having the bit

// on the predicate itself is used to avoid trying to push it down as a

// sargable predicate.

bool was_join_condition = false;

// If this is a join condition that came from a multiple equality,

// and we have decided to create a mesh from that multiple equality,

// returns the index of it into the “multiple_equalities” array

// in MakeJoinHypergraph(). (You don't actually need the array to

// use this; it's just an opaque index to deduplicate between different

// predicates.) Otherwise, -1.

int source_multiple_equality_idx = -1;

// See the equivalent fields in JoinPredicate.

FunctionalDependencySet functional_dependencies;

Mem_root_array<int> functional_dependencies_idx;

// The list of all subqueries referred to in this predicate, if any.

// The optimizer uses this to add their materialized/non-materialized

// costs when evaluating filters.

Mem_root_array<ContainedSubquery> contained_subqueries;

// Most of the members are declared with initializers, but bit fields cannot

// be declared with initializers until C++20, so we need to define a

// constructor to initialize those fields.

// TODO(khatlen): When we move to C++20, add initializers to the bit fields

// too, and use the default constructor generated by the compiler.

AccessPath()

: count_examined_rows(false)

#ifndef NDEBUG

,

forced_by_dbug(false)

#endif

{

}

enum Type : uint8_t {

// Basic access paths (those with no children, at least nominally).

// NOTE: When adding more paths to this section, also update GetBasicTable()

// to handle them.

TABLE_SCAN,

INDEX_SCAN,

REF,

REF_OR_NULL,

EQ_REF,

PUSHED_JOIN_REF,

FULL_TEXT_SEARCH,

CONST_TABLE,

MRR,

FOLLOW_TAIL,

INDEX_RANGE_SCAN,

INDEX_MERGE,

ROWID_INTERSECTION,

ROWID_UNION,

INDEX_SKIP_SCAN,

GROUP_INDEX_SKIP_SCAN,

DYNAMIC_INDEX_RANGE_SCAN,

// Basic access paths that don't correspond to a specific table.

TABLE_VALUE_CONSTRUCTOR,

FAKE_SINGLE_ROW,

ZERO_ROWS,

ZERO_ROWS_AGGREGATED,

MATERIALIZED_TABLE_FUNCTION,

UNQUALIFIED_COUNT,

// Joins.

NESTED_LOOP_JOIN,

NESTED_LOOP_SEMIJOIN_WITH_DUPLICATE_REMOVAL,

BKA_JOIN,

HASH_JOIN,

// Composite access paths.

FILTER,

SORT,

AGGREGATE,

TEMPTABLE_AGGREGATE,

LIMIT_OFFSET,

STREAM,

MATERIALIZE,

MATERIALIZE_INFORMATION_SCHEMA_TABLE,

APPEND,

WINDOW,

WEEDOUT,

REMOVE_DUPLICATES,

REMOVE_DUPLICATES_ON_INDEX,

ALTERNATIVE,

CACHE_INVALIDATOR,

// Access paths that modify tables.

DELETE_ROWS,

UPDATE_ROWS,

} type;

/// A general enum to describe the safety of a given operation.

/// Currently we only use this to describe row IDs, but it can easily

/// be reused for safety of updating a table we're reading from

/// (the Halloween problem), or just generally unreproducible results

/// (e.g. a TABLESAMPLE changing due to external factors).

///

/// Less safe values have higher numerical values.

enum Safety : uint8_t {

/// The given operation is always safe on this access path.

SAFE = 0,

/// The given operation is safe if this access path is scanned once,

/// but not if it's scanned multiple times (e.g. used on the inner side

/// of a nested-loop join). A typical example of this is a derived table

/// or CTE that is rematerialized on each scan, so that references to

/// the old values (such as row IDs) are no longer valid.

SAFE_IF_SCANNED_ONCE = 1,

/// The given operation is unsafe on this access path, no matter how many

/// or few times it's scanned. Often, it may help to materialize it

/// (assuming the materialization itself doesn't use the operation

/// in question).

UNSAFE = 2

};

/// Whether it is safe to get row IDs (for sorting) from this access path.

Safety safe_for_rowid = SAFE;

/// Whether this access path counts as one that scans a base table,

/// and thus should be counted towards examined_rows. It can sometimes

/// seem a bit arbitrary which iterators count towards examined_rows

/// and which ones do not, so the only canonical reference is the tests.

bool count_examined_rows : 1;

#ifndef NDEBUG

/// Whether this access path is forced preferred over all others by means

/// of a SET DEBUG force_subplan_0x... statement.

bool forced_by_dbug : 1;

#endif

/// For UPDATE and DELETE statements: The node index of a table which can be

/// updated or deleted from immediately as the rows are read from the

/// iterator, if this path is only read from once. -1 if there is no such

/// table in this path.

///

/// Note that this is an index into CostingReceiver's array of nodes, and is

/// not necessarily equal to the table number within the query block given by

/// Table_ref::tableno().

///

/// The table, if any, is currently always the outermost table in the path.

///

/// It is possible to have plans where it would be safe to operate

/// "immediately" on more than one table. For example, if we do a merge join,

/// it is safe to perform immediate deletes on tables on the inner side of the

/// join, since both sides are read only once. (However, we currently do not

/// support merge joins.)

///

/// Another possibility is when the outer table of a nested loop join is

/// guaranteed to return at most one row (typically, a unique index lookup

/// aka. eq_ref). Then it's safe to delete immediately from both sides of the

/// nested loop join. But we don't to this yet.

///

/// Hash joins read both sides exactly once, However, with hash joins, the

/// scans on the inner tables are not positioned on the correct row when the

/// result of the join is returned, so the immediate delete logic will need to

/// be changed to reposition the underlying scans before doing the immediate

/// deletes. While this can be done, it makes the benefit of immediate deletes

/// less obvious for these tables, and it can also be a loss in some cases,

/// because we lose the deduplication provided by the Unique object used for

/// buffered deletes (the immediate deletes could end up spending time

/// repositioning to already deleted rows). So we currently don't attempt to

/// do immediate deletes from inner tables of hash joins either.

///

/// The outer table of a hash join can be deleted from immediately if the

/// inner table fits in memory. If the hash join spills to disk, though,

/// neither the rows of the outer table nor the rows of the inner table come

/// out in the order of the underlying scan, so it is not safe in general to

/// perform immediate deletes on the outer table of a hash join.

///

/// If support for immediate operations on multiple tables is added,

/// this member could be changed from a node index to a NodeMap.

int8_t immediate_update_delete_table{-1};

/// Which ordering the rows produced by this path follow, if any

/// (see interesting_orders.h). This is really a LogicalOrderings::StateIndex,

/// but we don't want to add a dependency on interesting_orders.h from

/// this file, so we use the base type instead of the typedef here.

int ordering_state = 0;

/// If an iterator has been instantiated for this access path, points to the

/// iterator. Used for constructing iterators that need to talk to each other

/// (e.g. for recursive CTEs, or BKA join), and also for locating timing

/// information in EXPLAIN ANALYZE queries.

RowIterator *iterator = nullptr;

/// Expected cost to read all of this access path once; -1.0 for unknown.

double cost{-1.0};

/// Expected cost to initialize this access path; ie., cost to read

/// k out of N rows would be init_cost + (k/N) * (cost - init_cost).

/// Note that EXPLAIN prints out cost of reading the _first_ row

/// because it is easier for the user and also easier to measure in

/// EXPLAIN ANALYZE, but it is easier to do calculations with a pure

/// initialization cost, so that is what we use in this member.

/// -1.0 for unknown.

double init_cost{-1.0};

/// Of init_cost, how much of the initialization needs only to be done

/// once per query block. (This is a cost, not a proportion.)

/// Ie., if the access path can reuse some its initialization work

/// if Init() is called multiple times, this member will be nonzero.

/// A typical example is a materialized table with rematerialize=false;

/// the second time Init() is called, it's a no-op. Most paths will have

/// init_once_cost = 0.0, ie., repeated scans will cost the same.

/// We do not intend to use this field to model cache effects.

///

/// This is currently not printed in EXPLAIN, only optimizer trace.

double init_once_cost{0.0};

/// Return the cost of scanning the given path for the second time

/// (or later) in the given query block. This is really the interesting

/// metric, not init_once_cost in itself, but since nearly all paths

/// have zero init_once_cost, storing that instead allows us to skip

/// a lot of repeated path->init_once_cost = path->init_cost calls

/// in the code.

double rescan_cost() const { return cost - init_once_cost; }

/// If no filter, identical to num_output_rows, cost, respectively.

/// init_cost is always the same (filters have zero initialization cost).

double num_output_rows_before_filter{kUnknownRowCount},

cost_before_filter{-1.0};

/// Bitmap of WHERE predicates that we are including on this access path,

/// referring to the “predicates” array internal to the join optimizer.

/// Since bit masks are much cheaper to deal with than creating Item

/// objects, and we don't invent new conditions during join optimization

/// (all of them are known when we begin optimization), we stick to

/// manipulating bit masks during optimization, saying which filters will be

/// applied at this node (a 1-bit means the filter will be applied here; if

/// there are multiple ones, they are ANDed together).

///

/// This is used during join optimization only; before iterators are

/// created, we will add FILTER access paths to represent these instead,

/// removing the dependency on the array. Said FILTER paths are by

/// convention created with materialize_subqueries = false, since the by far

/// most common case is that there are no subqueries in the predicate.

/// In other words, if you wish to represent a filter with

/// materialize_subqueries = true, you will need to make an explicit FILTER

/// node.

///

/// See also nested_loop_join().equijoin_predicates, which is for filters

/// being applied _before_ nested-loop joins, but is otherwise the same idea.

OverflowBitset filter_predicates{0};

/// Bitmap of sargable join predicates that have already been applied

/// in this access path by means of an index lookup (ref access),

/// again referring to “predicates”, and thus should not be counted again

/// for selectivity. Note that the filter may need to be applied

/// nevertheless (especially in case of type conversions); see

/// subsumed_sargable_join_predicates.

///

/// Since these refer to the same array as filter_predicates, they will

/// never overlap with filter_predicates, and so we can reuse the same

/// memory using an alias (a union would not be allowed, since OverflowBitset

/// is a class with non-trivial default constructor), even though the meaning

/// is entirely separate. If N = num_where_predicates in the hypergraph, then

/// bits 0..(N-1) belong to filter_predicates, and the rest to

/// applied_sargable_join_predicates.

OverflowBitset &applied_sargable_join_predicates() {

return filter_predicates;

}

const OverflowBitset &applied_sargable_join_predicates() const {

return filter_predicates;

}

/// Bitmap of WHERE predicates that touch tables we have joined in,

/// but that we could not apply yet (for instance because they reference

/// other tables, or because because we could not push them down into

/// the nullable side of outer joins). Used during planning only

/// (see filter_predicates).

OverflowBitset delayed_predicates{0};

/// Similar to applied_sargable_join_predicates, bitmap of sargable

/// join predicates that have been applied and will subsume the join

/// predicate entirely, ie., not only should the selectivity not be

/// double-counted, but the predicate itself is redundant and need not

/// be applied as a filter. (It is an error to have a bit set here but not

/// in applied_sargable_join_predicates.)

OverflowBitset &subsumed_sargable_join_predicates() {

return delayed_predicates;

}

const OverflowBitset &subsumed_sargable_join_predicates() const {

return delayed_predicates;

}

/// If nonzero, a bitmap of other tables whose joined-in rows must already be

/// loaded when rows from this access path are evaluated; that is, this

/// access path must be put on the inner side of a nested-loop join (or

/// multiple such joins) where the outer side includes all of the given

/// tables.

///

/// The most obvious case for this is dependent tables in LATERAL, but a more

/// common case is when we have pushed join conditions referring to those

/// tables; e.g., if this access path represents t1 and we have a condition

/// t1.x=t2.x that is pushed down into an index lookup (ref access), t2 will

/// be set in this bitmap. We can still join in other tables, deferring t2,

/// but the bit(s) will then propagate, and we cannot be on the right side of

/// a hash join until parameter_tables is zero again. (Also see

/// DisallowParameterizedJoinPath() for when we disallow such deferring,

/// as an optimization.)

///

/// As a special case, we allow setting RAND_TABLE_BIT, even though it

/// is normally part of a table_map, not a NodeMap. In this case, it specifies

/// that the access path is entirely noncachable, because it depends on

/// something nondeterministic or an outer reference, and thus can never be on

/// the right side of a hash join, ever.

hypergraph::NodeMap parameter_tables{0};

/// Auxiliary data used by a secondary storage engine while processing the

/// access path during optimization and execution. The secondary storage

/// engine is free to store any useful information in this member, for example

/// extra statistics or cost estimates. The data pointed to is fully owned by

/// the secondary storage engine, and it is the responsibility of the

/// secondary engine to manage the memory and make sure it is properly

/// destroyed.

void *secondary_engine_data{nullptr};

// Accessors for the union below.

auto &table_scan() {

assert(type == TABLE_SCAN);

return u.table_scan;

}

const auto &table_scan() const {

assert(type == TABLE_SCAN);

return u.table_scan;

}

auto &index_scan() {

assert(type == INDEX_SCAN);

return u.index_scan;

}

const auto &index_scan() const {

assert(type == INDEX_SCAN);

return u.index_scan;

}

auto &ref() {

assert(type == REF);

return u.ref;

}

const auto &ref() const {

assert(type == REF);

return u.ref;

}

auto &ref_or_null() {

assert(type == REF_OR_NULL);

return u.ref_or_null;

}

const auto &ref_or_null() const {

assert(type == REF_OR_NULL);

return u.ref_or_null;

}

auto &eq_ref() {

assert(type == EQ_REF);

return u.eq_ref;

}

const auto &eq_ref() const {

assert(type == EQ_REF);

return u.eq_ref;

}

auto &pushed_join_ref() {

assert(type == PUSHED_JOIN_REF);

return u.pushed_join_ref;

}

const auto &pushed_join_ref() const {

assert(type == PUSHED_JOIN_REF);

return u.pushed_join_ref;

}

auto &full_text_search() {

assert(type == FULL_TEXT_SEARCH);

return u.full_text_search;

}

const auto &full_text_search() const {

assert(type == FULL_TEXT_SEARCH);

return u.full_text_search;

}

auto &const_table() {

assert(type == CONST_TABLE);

return u.const_table;

}

const auto &const_table() const {

assert(type == CONST_TABLE);

return u.const_table;

}

auto &mrr() {

assert(type == MRR);

return u.mrr;

}

const auto &mrr() const {

assert(type == MRR);

return u.mrr;

}

auto &follow_tail() {

assert(type == FOLLOW_TAIL);

return u.follow_tail;

}

const auto &follow_tail() const {

assert(type == FOLLOW_TAIL);

return u.follow_tail;

}

auto &index_range_scan() {

assert(type == INDEX_RANGE_SCAN);

return u.index_range_scan;

}

const auto &index_range_scan() const {

assert(type == INDEX_RANGE_SCAN);

return u.index_range_scan;

}

auto &index_merge() {

assert(type == INDEX_MERGE);

return u.index_merge;

}

const auto &index_merge() const {

assert(type == INDEX_MERGE);

return u.index_merge;

}

auto &rowid_intersection() {

assert(type == ROWID_INTERSECTION);

return u.rowid_intersection;

}

const auto &rowid_intersection() const {

assert(type == ROWID_INTERSECTION);

return u.rowid_intersection;

}

auto &rowid_union() {

assert(type == ROWID_UNION);

return u.rowid_union;

}

const auto &rowid_union() const {

assert(type == ROWID_UNION);

return u.rowid_union;

}

auto &index_skip_scan() {

assert(type == INDEX_SKIP_SCAN);

return u.index_skip_scan;

}

const auto &index_skip_scan() const {

assert(type == INDEX_SKIP_SCAN);

return u.index_skip_scan;

}

auto &group_index_skip_scan() {

assert(type == GROUP_INDEX_SKIP_SCAN);

return u.group_index_skip_scan;

}

const auto &group_index_skip_scan() const {

assert(type == GROUP_INDEX_SKIP_SCAN);

return u.group_index_skip_scan;

}

auto &dynamic_index_range_scan() {

assert(type == DYNAMIC_INDEX_RANGE_SCAN);

return u.dynamic_index_range_scan;

}

const auto &dynamic_index_range_scan() const {

assert(type == DYNAMIC_INDEX_RANGE_SCAN);

return u.dynamic_index_range_scan;

}

auto &materialized_table_function() {

assert(type == MATERIALIZED_TABLE_FUNCTION);

return u.materialized_table_function;

}

const auto &materialized_table_function() const {

assert(type == MATERIALIZED_TABLE_FUNCTION);

return u.materialized_table_function;

}

auto &unqualified_count() {

assert(type == UNQUALIFIED_COUNT);

return u.unqualified_count;

}

const auto &unqualified_count() const {

assert(type == UNQUALIFIED_COUNT);

return u.unqualified_count;

}

auto &table_value_constructor() {

assert(type == TABLE_VALUE_CONSTRUCTOR);

return u.table_value_constructor;

}

const auto &table_value_constructor() const {

assert(type == TABLE_VALUE_CONSTRUCTOR);

return u.table_value_constructor;

}

auto &fake_single_row() {

assert(type == FAKE_SINGLE_ROW);

return u.fake_single_row;

}

const auto &fake_single_row() const {

assert(type == FAKE_SINGLE_ROW);

return u.fake_single_row;

}

auto &zero_rows() {

assert(type == ZERO_ROWS);

return u.zero_rows;

}

const auto &zero_rows() const {

assert(type == ZERO_ROWS);

return u.zero_rows;

}

auto &zero_rows_aggregated() {

assert(type == ZERO_ROWS_AGGREGATED);

return u.zero_rows_aggregated;

}

const auto &zero_rows_aggregated() const {

assert(type == ZERO_ROWS_AGGREGATED);

return u.zero_rows_aggregated;

}

auto &hash_join() {

assert(type == HASH_JOIN);

return u.hash_join;

}

const auto &hash_join() const {

assert(type == HASH_JOIN);

return u.hash_join;

}

auto &bka_join() {

assert(type == BKA_JOIN);

return u.bka_join;

}

const auto &bka_join() const {

assert(type == BKA_JOIN);

return u.bka_join;

}

auto &nested_loop_join() {

assert(type == NESTED_LOOP_JOIN);

return u.nested_loop_join;

}

const auto &nested_loop_join() const {

assert(type == NESTED_LOOP_JOIN);

return u.nested_loop_join;

}

auto &nested_loop_semijoin_with_duplicate_removal() {

assert(type == NESTED_LOOP_SEMIJOIN_WITH_DUPLICATE_REMOVAL);

return u.nested_loop_semijoin_with_duplicate_removal;

}

const auto &nested_loop_semijoin_with_duplicate_removal() const {

assert(type == NESTED_LOOP_SEMIJOIN_WITH_DUPLICATE_REMOVAL);

return u.nested_loop_semijoin_with_duplicate_removal;

}

auto &filter() {

assert(type == FILTER);

return u.filter;

}

const auto &filter() const {

assert(type == FILTER);

return u.filter;

}

auto &sort() {

assert(type == SORT);

return u.sort;

}

const auto &sort() const {

assert(type == SORT);

return u.sort;

}

auto &aggregate() {

assert(type == AGGREGATE);

return u.aggregate;

}

const auto &aggregate() const {

assert(type == AGGREGATE);

return u.aggregate;

}

auto &temptable_aggregate() {

assert(type == TEMPTABLE_AGGREGATE);

return u.temptable_aggregate;

}

const auto &temptable_aggregate() const {

assert(type == TEMPTABLE_AGGREGATE);

return u.temptable_aggregate;

}

auto &limit_offset() {

assert(type == LIMIT_OFFSET);

return u.limit_offset;

}

const auto &limit_offset() const {

assert(type == LIMIT_OFFSET);

return u.limit_offset;

}

auto &stream() {

assert(type == STREAM);

return u.stream;

}

const auto &stream() const {

assert(type == STREAM);

return u.stream;

}

auto &materialize() {

assert(type == MATERIALIZE);

return u.materialize;

}

const auto &materialize() const {

assert(type == MATERIALIZE);

return u.materialize;

}

auto &materialize_information_schema_table() {

assert(type == MATERIALIZE_INFORMATION_SCHEMA_TABLE);

return u.materialize_information_schema_table;

}

const auto &materialize_information_schema_table() const {

assert(type == MATERIALIZE_INFORMATION_SCHEMA_TABLE);

return u.materialize_information_schema_table;

}

auto &append() {

assert(type == APPEND);

return u.append;

}

const auto &append() const {

assert(type == APPEND);

return u.append;

}

auto &window() {

assert(type == WINDOW);

return u.window;

}

const auto &window() const {

assert(type == WINDOW);

return u.window;

}

auto &weedout() {

assert(type == WEEDOUT);

return u.weedout;

}

const auto &weedout() const {

assert(type == WEEDOUT);

return u.weedout;

}

auto &remove_duplicates() {

assert(type == REMOVE_DUPLICATES);

return u.remove_duplicates;

}

const auto &remove_duplicates() const {

assert(type == REMOVE_DUPLICATES);

return u.remove_duplicates;

}

auto &remove_duplicates_on_index() {

assert(type == REMOVE_DUPLICATES_ON_INDEX);

return u.remove_duplicates_on_index;

}

const auto &remove_duplicates_on_index() const {

assert(type == REMOVE_DUPLICATES_ON_INDEX);

return u.remove_duplicates_on_index;

}

auto &alternative() {

assert(type == ALTERNATIVE);

return u.alternative;

}

const auto &alternative() const {

assert(type == ALTERNATIVE);

return u.alternative;

}

auto &cache_invalidator() {

assert(type == CACHE_INVALIDATOR);

return u.cache_invalidator;

}

const auto &cache_invalidator() const {

assert(type == CACHE_INVALIDATOR);

return u.cache_invalidator;

}

auto &delete_rows() {

assert(type == DELETE_ROWS);

return u.delete_rows;

}

const auto &delete_rows() const {

assert(type == DELETE_ROWS);

return u.delete_rows;

}

auto &update_rows() {

assert(type == UPDATE_ROWS);

return u.update_rows;

}

const auto &update_rows() const {

assert(type == UPDATE_ROWS);

return u.update_rows;

}

double num_output_rows() const { return m_num_output_rows; }

void set_num_output_rows(double val) { m_num_output_rows = val; }

private:

/// Expected number of output rows, -1.0 for unknown.

double m_num_output_rows{kUnknownRowCount};

// We'd prefer if this could be an std::variant, but we don't have C++17 yet.

// It is private to force all access to be through the type-checking

// accessors.

//

// For information about the meaning of each value, see the corresponding

// row iterator constructors.

union {

struct {

TABLE *table;

} table_scan;

struct {

TABLE *table;

int idx;

bool use_order;

bool reverse;

} index_scan;

struct {

TABLE *table;

Index_lookup *ref;

bool use_order;

bool reverse;

} ref;

struct {

TABLE *table;

Index_lookup *ref;

bool use_order;

} ref_or_null;

struct {

TABLE *table;

Index_lookup *ref;

} eq_ref;

struct {

TABLE *table;

Index_lookup *ref;

bool use_order;

bool is_unique;

} pushed_join_ref;

struct {

TABLE *table;

Index_lookup *ref;

bool use_order;

bool use_limit;

Item_func_match *ft_func;

} full_text_search;

struct {

TABLE *table;

Index_lookup *ref;

} const_table;

struct {

TABLE *table;

Index_lookup *ref;

AccessPath *bka_path;

int mrr_flags;

bool keep_current_rowid;

} mrr;

struct {

TABLE *table;

} follow_tail;

struct {

// The key part(s) we are scanning on. Note that this may be an array.

// You can get the table we are working on by looking into

// used_key_parts[0].field->table (it is not stored directly, to avoid

// going over the AccessPath size limits).

KEY_PART *used_key_part;

// The actual ranges we are scanning over (originally derived from “key”).

// Not a Bounds_checked_array, to save 4 bytes on the length.

QUICK_RANGE **ranges;

unsigned num_ranges;

unsigned mrr_flags;

unsigned mrr_buf_size;

// Which index (in the TABLE) we are scanning over, and how many of its

// key parts we are using.

unsigned index;

unsigned num_used_key_parts;

// If true, the scan can return rows in rowid order.

bool can_be_used_for_ror : 1;

// If true, the scan _should_ return rows in rowid order.

// Should only be set if can_be_used_for_ror == true.

bool need_rows_in_rowid_order : 1;

// If true, this plan can be used for index merge scan.

bool can_be_used_for_imerge : 1;

// See row intersection for more details.

bool reuse_handler : 1;

// Whether we are scanning over a geometry key part.

bool geometry : 1;

// Whether we need a reverse scan. Only supported if geometry == false.

bool reverse : 1;

// For a reverse scan, if we are using extended key parts. It is needed,

// to set correct flags when retrieving records.

bool using_extended_key_parts : 1;

} index_range_scan;

struct {

TABLE *table;

bool forced_by_hint;

bool allow_clustered_primary_key_scan;

Mem_root_array<AccessPath *> *children;

} index_merge;

struct {

TABLE *table;

Mem_root_array<AccessPath *> *children;

// Clustered primary key scan, if any.

AccessPath *cpk_child;

bool forced_by_hint;

bool retrieve_full_rows;

bool need_rows_in_rowid_order;

// If true, the first child scan should reuse table->file instead of

// creating its own. This is true if the intersection is the topmost

// range scan, but _not_ if it's below a union. (The reasons for this

// are unknown.) It can also be negated by logic involving

// retrieve_full_rows and is_covering, again for unknown reasons.

//

// This is not only for performance; multi-table delete has a hidden

// dependency on this behavior when running against certain types of

// tables (e.g. MyISAM), as it assumes table->file is correctly positioned

// when deleting (and not all table types can transfer the position of one

// handler to another by using position()).

bool reuse_handler;

// true if no row retrieval phase is necessary.

bool is_covering;

} rowid_intersection;

struct {

TABLE *table;

Mem_root_array<AccessPath *> *children;

bool forced_by_hint;

} rowid_union;

struct {

TABLE *table;

unsigned index;

unsigned num_used_key_parts;

bool forced_by_hint;

// Large, and has nontrivial destructors, so split out into