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这篇文章主要为大家展示了“PostgreSQL中PlannedStmt的跟踪分析”,内容简而易懂,条理清晰,希望能够帮助大家解决疑惑,下面让小编带领大家一起研究并学习一下“PostgreSQL中PlannedStmt的跟踪分析”这篇文章吧。
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计划树
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;
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