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计划树
二、数据结构
Plan
/* ----------------
* Plan node
*
* All plan nodes derive from the Plan structure by having the
* Plan structure as the first field. This ensures that everything works
* when nodes are cast to Plan s. (node pointers are frequently cast to Plan*
* when passed around generically in the executor)
*
* We never actually instantiate any Plan nodes; this is just the common
* abstract superclass for all Plan-type nodes.
* ----------------
*/
typedef struct Plan
{
NodeTag type;
/*
* estimated execution costs for plan (see costsize.c for more info)
*/
Cost startup_cost; /* cost expended before fetching any tuples */
Cost total_cost; /* total cost (assuming all tuples fetched) */
/*
* planner s estimate of result size of this plan step
*/
double plan_rows; /* number of rows plan is expected to emit */
int plan_width; /* average row width in bytes */
/*
* information needed for parallel query
*/
bool parallel_aware; /* engage parallel-aware logic? */
bool parallel_safe; /* OK to use as part of parallel plan? */
/*
* Common structural data for all Plan types.
*/
int plan_node_id; /* unique across entire final plan tree */
List *targetlist; /* target list to be computed at this node */
List *qual; /* implicitly-ANDed qual conditions */
struct Plan *lefttree; /* input plan tree(s) */
struct Plan *righttree;
List *initPlan; /* Init Plan nodes (un-correlated expr
* subselects) */
/*
* Information for management of parameter-change-driven rescanning
*
* extParam includes the paramIDs of all external PARAM_EXEC params
* affecting this plan node or its children. setParam params from the
* node s initPlans are not included, but their extParams are.
*
* allParam includes all the extParam paramIDs, plus the IDs of local
* params that affect the node (i.e., the setParams of its initplans).
* These are _all_ the PARAM_EXEC params that affect this node.
*/
Bitmapset *extParam;
Bitmapset *allParam;
} Plan;Limit
/* ----------------
* limit node
*
* Note: as of Postgres 8.2, the offset and count expressions are expected
* to yield int8, rather than int4 as before.
* ----------------
*/
typedef struct Limit
{
Plan plan;
Node *limitOffset; /* OFFSET parameter, or NULL if none */
Node *limitCount; /* COUNT parameter, or NULL if none */
} Limit;Sort
/* ----------------
* sort node
* ----------------
*/
typedef struct Sort
{
Plan plan;
int numCols; /* number of sort-key columns */
AttrNumber *sortColIdx; /* their indexes in the target list */
Oid *sortOperators; /* OIDs of operators to sort them by */
Oid *collations; /* OIDs of collations */
bool *nullsFirst; /* NULLS FIRST/LAST directions */
} Sort;Append
/* ----------------
* Append node -
* Generate the concatenation of the results of sub-plans.
* ----------------
*/
typedef struct Append
{
Plan plan;
List *appendplans;
/*
* All appendplans preceding this index are non-partial plans. All
* appendplans from this index onwards are partial plans.
*/
int first_partial_plan;
/* RT indexes of non-leaf tables in a partition tree */
List *partitioned_rels;
/* Info for run-time subplan pruning; NULL if we re not doing that */
struct PartitionPruneInfo *part_prune_info;
} Append;NestLoop
/* ----------------
* nest loop join node
*
* The nestParams list identifies any executor Params that must be passed
* into execution of the inner subplan carrying values from the current row
* of the outer subplan. Currently we restrict these values to be simple
* Vars, but perhaps someday that d be worth relaxing. (Note: during plan
* creation, the paramval can actually be a PlaceHolderVar expression; but it
* must be a Var with varno OUTER_VAR by the time it gets to the executor.)
* ----------------
*/
typedef struct NestLoop
{
Join join;
List *nestParams; /* list of NestLoopParam nodes */
} NestLoop;
typedef struct NestLoopParam
{
NodeTag type;
int paramno; /* number of the PARAM_EXEC Param to set */
Var *paramval; /* outer-relation Var to assign to Param */
} NestLoopParam;
/*
* ==========
* Join nodes
* ==========
*/
/* ----------------
* merge join node
*
* The expected ordering of each mergeable column is described by a btree
* opfamily OID, a collation OID, a direction (BTLessStrategyNumber or
* BTGreaterStrategyNumber) and a nulls-first flag. Note that the two sides
* of each mergeclause may be of different datatypes, but they are ordered the
* same way according to the common opfamily and collation. The operator in
* each mergeclause must be an equality operator of the indicated opfamily.
* ----------------
*/
typedef struct MergeJoin
{
Join join;
bool skip_mark_restore; /* Can we skip mark/restore calls? */
List *mergeclauses; /* mergeclauses as expression trees */
/* these are arrays, but have the same length as the mergeclauses list: */
Oid *mergeFamilies; /* per-clause OIDs of btree opfamilies */
Oid *mergeCollations; /* per-clause OIDs of collations */
int *mergeStrategies; /* per-clause ordering (ASC or DESC) */
bool *mergeNullsFirst; /* per-clause nulls ordering */
} MergeJoin;
/* ----------------
* hash join node
* ----------------
*/
typedef struct HashJoin
{
Join join;
List *hashclauses;
} HashJoin;
/* ----------------
* Join node
*
* jointype: rule for joining tuples from left and right subtrees
* inner_unique each outer tuple can match to no more than one inner tuple
* joinqual: qual conditions that came from JOIN/ON or JOIN/USING
* (plan.qual contains conditions that came from WHERE)
*
* When jointype is INNER, joinqual and plan.qual are semantically
* interchangeable. For OUTER jointypes, the two are *not* interchangeable;
* only joinqual is used to determine whether a match has been found for
* the purpose of deciding whether to generate null-extended tuples.
* (But plan.qual is still applied before actually returning a tuple.)
* For an outer join, only joinquals are allowed to be used as the merge
* or hash condition of a merge or hash join.
*
* inner_unique is set if the joinquals are such that no more than one inner
* tuple could match any given outer tuple. This allows the executor to
* skip searching for additional matches. (This must be provable from just
* the joinquals, ignoring plan.qual, due to where the executor tests it.)
* ----------------
*/
typedef struct Join
{
Plan plan;
JoinType jointype;
bool inner_unique;
List *joinqual; /* JOIN quals (in addition to plan.qual) */
} Join;SeqScan
/*
* ==========
* Scan nodes
* ==========
*/
typedef struct Scan
{
Plan plan;
Index scanrelid; /* relid is index into the range table */
} Scan;
/* ----------------
* sequential scan node
* ----------------
*/
typedef Scan SeqScan;以上是“PostgreSQL 中 PlannedStmt 的跟踪分析”这篇文章的所有内容，感谢各位的阅读！相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注丸趣 TV 行业资讯频道！
正文完
发表至： 数据库
2023-07-20
