path_utils.c

/*
 *******************************************************************************
 *
 *	EXTRACTING PATH INFORMATION UTILITIES
 *
 *******************************************************************************
 *
 * Copyright (c) 2016-2021, Postgres Professional
 *
 * IDENTIFICATION
 *	  aqo/path_utils.c
 *
 */

#include "postgres.h"

#include "nodes/readfuncs.h"
#include "optimizer/optimizer.h"
#include "path_utils.h"

#include "aqo.h"
#include "hash.h"


/*
 * Hook on creation of a plan node. We need to store AQO-specific data to
 * support learning stage.
 */
create_plan_hook_type prev_create_plan_hook = NULL;

create_upper_paths_hook_type prev_create_upper_paths_hook = NULL;

static AQOPlanNode DefaultAQOPlanNode =
{
	.node.type = T_ExtensibleNode,
	.node.extnodename = AQO_PLAN_NODE,
	.had_path = false,
	.relids = NIL,
	.clauses = NIL,
	.selectivities = NIL,
	.grouping_exprs = NIL,
	.jointype = -1,
	.parallel_divisor = -1,
	.was_parametrized = false,
	.fss = INT_MAX,
	.prediction = -1
};

static AQOPlanNode *
create_aqo_plan_node()
{
	AQOPlanNode *node = (AQOPlanNode *) newNode(sizeof(AQOPlanNode),
															T_ExtensibleNode);

	memcpy(node, &DefaultAQOPlanNode, sizeof(AQOPlanNode));
	return node;
}

AQOPlanNode *
get_aqo_plan_node(Plan *plan, bool create)
{
	AQOPlanNode *node = NULL;
	ListCell	*lc;

	foreach(lc, plan->private)
	{
		AQOPlanNode *candidate = (AQOPlanNode *) lfirst(lc);

		if (!IsA(candidate, ExtensibleNode))
			continue;

		if (strcmp(candidate->node.extnodename, AQO_PLAN_NODE) != 0)
			continue;

		node = candidate;
		break;
	}

	if (node == NULL)
	{
		if (!create)
			return &DefaultAQOPlanNode;

		node = create_aqo_plan_node();
		plan->private = lappend(plan->private, node);
	}

	Assert(node);
	return node;
}

/*
 * Returns list of marginal selectivities using as an arguments for each clause
 * (root, clause, 0, jointype, NULL).
 * That is not quite correct for parameterized baserel and foreign key join
 * cases, but nevertheless that is bearable.
 */
List *
get_selectivities(PlannerInfo *root,
				  List *clauses,
				  int varRelids,
				  JoinType jointype,
				  SpecialJoinInfo *sjinfo)
{
	List	   *res = NIL;
	ListCell   *l;
	double	   *elem;

	foreach(l, clauses)
	{
		elem = palloc(sizeof(*elem));
		*elem = clause_selectivity(root, lfirst(l), varRelids,
								   jointype, sjinfo);
		res = lappend(res, elem);
	}

	return res;
}

/*
 * Transforms given relids from path optimization stage format to list of
 * an absolute (independent on query optimization context) relids.
 */
List *
get_list_of_relids(PlannerInfo *root, Relids relids)
{
	int			i;
	RangeTblEntry *entry;
	List	   *l = NIL;

	if (relids == NULL)
		return NIL;

	/*
	 * Check: don't take into account relations without underlying plane
	 * source table.
	 */
	Assert(!bms_is_member(0, relids));

	i = -1;
	while ((i = bms_next_member(relids, i)) >= 0)
	{
		entry = planner_rt_fetch(i, root);
		if (OidIsValid(entry->relid))
			l = lappend_int(l, entry->relid);
	}
	return l;
}

/*
 * Search for any subplans or initplans.
 * if subplan is found, replace it by the feature space value of this subplan.
 */
static Node *
subplan_hunter(Node *node, void *context)
{
	if (node == NULL)
		/* Continue recursion in other subtrees. */
		return false;

	if (IsA(node, SubPlan))
	{
		SubPlan		*splan = (SubPlan *) node;
		PlannerInfo	*root = (PlannerInfo *) context;
		PlannerInfo	*subroot;
		RelOptInfo	*upper_rel;
		A_Const		*fss;

		subroot = (PlannerInfo *) list_nth(root->glob->subroots,
										   splan->plan_id - 1);
		upper_rel = fetch_upper_rel(subroot, UPPERREL_FINAL, NULL);

		Assert(list_length(upper_rel->private) == 1);
		Assert(IsA((Node *) linitial(upper_rel->private), A_Const));

		fss = (A_Const *) linitial(upper_rel->private);
		return (Node *) copyObject(fss);
	}
	return expression_tree_mutator(node, subplan_hunter, context);
}

/*
 * Get independent copy of the clauses list.
 * During this operation clauses could be changed and we couldn't walk across
 * this list next.
 */
List *
aqo_get_clauses(PlannerInfo *root, List *restrictlist)
{
	List		*clauses = NIL;
	ListCell	*lc;

	foreach(lc, restrictlist)
	{
		RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);

		rinfo = copyObject(rinfo);
		rinfo->clause = (Expr *) expression_tree_mutator((Node *) rinfo->clause,
														 subplan_hunter,
														 (void *) root);
		clauses = lappend(clauses, (void *) rinfo);
	}
	return clauses;
}

/*
 * For given path returns the list of all clauses used in it.
 * Also returns selectivities for the clauses throw the selectivities variable.
 * Both clauses and selectivities returned lists are copies and therefore
 * may be modified without corruption of the input data.
 */
List *
get_path_clauses(Path *path, PlannerInfo *root, List **selectivities)
{
	List	   *inner;
	List	   *inner_sel = NIL;
	List	   *outer;
	List	   *outer_sel = NIL;
	List	   *cur = NIL;
	List	   *cur_sel = NIL;

	Assert(selectivities != NULL);
	*selectivities = NIL;

	if (path == NULL)
		return NIL;

	switch (path->type)
	{
		case T_NestPath:
		case T_MergePath:
		case T_HashPath:
			cur = ((JoinPath *) path)->joinrestrictinfo;

			/* Not quite correct to avoid sjinfo, but we believe in caching */
			cur_sel = get_selectivities(root, cur, 0,
										((JoinPath *) path)->jointype,
										NULL);

			outer = get_path_clauses(((JoinPath *) path)->outerjoinpath, root,
									 &outer_sel);
			inner = get_path_clauses(((JoinPath *) path)->innerjoinpath, root,
									 &inner_sel);
			*selectivities = list_concat(cur_sel,
										 list_concat(outer_sel, inner_sel));
			return list_concat(list_copy(cur), list_concat(outer, inner));
			break;
		case T_UniquePath:
			return get_path_clauses(((UniquePath *) path)->subpath, root,
									selectivities);
			break;
		case T_GatherPath:
		case T_GatherMergePath:
			return get_path_clauses(((GatherPath *) path)->subpath, root,
									selectivities);
			break;
		case T_MaterialPath:
			return get_path_clauses(((MaterialPath *) path)->subpath, root,
									selectivities);
			break;
		case T_ProjectionPath:
			return get_path_clauses(((ProjectionPath *) path)->subpath, root,
									selectivities);
			break;
		case T_SortPath:
			return get_path_clauses(((SortPath *) path)->subpath, root,
									selectivities);
			break;
		case T_GroupPath:
			return get_path_clauses(((GroupPath *) path)->subpath, root,
									selectivities);
			break;
		case T_UpperUniquePath:
			return get_path_clauses(((UpperUniquePath *) path)->subpath, root,
									selectivities);
			break;
		case T_AggPath:
			return get_path_clauses(((AggPath *) path)->subpath, root,
									selectivities);
			break;
		case T_GroupingSetsPath:
			return get_path_clauses(((GroupingSetsPath *) path)->subpath, root,
									selectivities);
			break;
		case T_WindowAggPath:
			return get_path_clauses(((WindowAggPath *) path)->subpath, root,
									selectivities);
			break;
		case T_SetOpPath:
			return get_path_clauses(((SetOpPath *) path)->subpath, root,
									selectivities);
			break;
		case T_LockRowsPath:
			return get_path_clauses(((LockRowsPath *) path)->subpath, root,
									selectivities);
			break;
		case T_LimitPath:
			return get_path_clauses(((LimitPath *) path)->subpath, root,
									selectivities);
			break;
		case T_SubqueryScanPath:
			return get_path_clauses(((SubqueryScanPath *) path)->subpath, root,
									selectivities);
			break;
		case T_AppendPath:
		{
			ListCell *lc;

			foreach (lc, ((AppendPath *) path)->subpaths)
			{
				Path *subpath = lfirst(lc);

				cur = list_concat(cur, list_copy(
					get_path_clauses(subpath, root, selectivities)));
				cur_sel = list_concat(cur_sel, *selectivities);
			}
			cur = list_concat(cur, aqo_get_clauses(root,
											path->parent->baserestrictinfo));
			*selectivities = list_concat(cur_sel,
										 get_selectivities(root,
											path->parent->baserestrictinfo,
											0, JOIN_INNER, NULL));
			return cur;
		}
			break;
		case T_ForeignPath:
			/* The same as in the default case */
		default:
			cur = list_concat(aqo_get_clauses(root,
											  path->parent->baserestrictinfo),
							  path->param_info ?
							  aqo_get_clauses(root,
											  path->param_info->ppi_clauses) :
							  NIL);
			if (path->param_info)
				cur_sel = get_selectivities(root, cur, path->parent->relid,
											JOIN_INNER, NULL);
			else
				cur_sel = get_selectivities(root, cur, 0, JOIN_INNER, NULL);
			*selectivities = cur_sel;
			return cur;
			break;
	}
}

/*
 * Converts path info into plan node for collecting it after query execution.
 */
void
aqo_create_plan_hook(PlannerInfo *root, Path *src, Plan **dest)
{
	bool is_join_path;
	Plan *plan = *dest;
	AQOPlanNode	*node;

	if (prev_create_plan_hook)
		prev_create_plan_hook(root, src, dest);

	if (!query_context.use_aqo && !query_context.learn_aqo)
		return;

	is_join_path = (src->type == T_NestPath || src->type == T_MergePath ||
					src->type == T_HashPath);

	node = get_aqo_plan_node(plan, true);

	if (node->had_path)
	{
		/*
		 * The convention is that any extension that sets had_path is also
		 * responsible for setting path_clauses, path_jointype, path_relids,
		 * path_parallel_workers, and was_parameterized.
		 */
		return;
	}

	if (is_join_path)
	{
		node->clauses = aqo_get_clauses(root, ((JoinPath *) src)->joinrestrictinfo);
		node->jointype = ((JoinPath *) src)->jointype;
	}
	else if (IsA(src, AggPath))
	/* Aggregation node must store grouping clauses. */
	{
		AggPath *ap = (AggPath *) src;

		/* Get TLE's from child target list corresponding to the list of exprs. */
		List *groupExprs = get_sortgrouplist_exprs(ap->groupClause,
												(*dest)->lefttree->targetlist);
		/* Copy bare expressions for further AQO learning case. */
		node->grouping_exprs = copyObject(groupExprs);
		node->relids = get_list_of_relids(root, ap->subpath->parent->relids);
		node->jointype = JOIN_INNER;
	}
	else
	{
		node->clauses = list_concat(
			aqo_get_clauses(root, src->parent->baserestrictinfo),
				src->param_info ? aqo_get_clauses(root, src->param_info->ppi_clauses) : NIL);
		node->jointype = JOIN_INNER;
	}

	node->relids = list_concat(node->relids,
								get_list_of_relids(root, src->parent->relids));

	if (src->parallel_workers > 0)
		node->parallel_divisor = get_parallel_divisor(src);
	node->was_parametrized = (src->param_info != NULL);

	if (src->param_info)
	{
		node->prediction = src->param_info->predicted_ppi_rows;
		node->fss = src->param_info->fss_ppi_hash;
	}
	else
	{
		node->prediction = src->parent->predicted_cardinality;
		node->fss = src->parent->fss_hash;
	}

	node->had_path = true;
}

static void
AQOnodeCopy(struct ExtensibleNode *enew, const struct ExtensibleNode *eold)
{
	AQOPlanNode *new = (AQOPlanNode *) enew;
	AQOPlanNode *old = (AQOPlanNode *) eold;

	Assert(IsA(old, ExtensibleNode));
	Assert(strcmp(old->node.extnodename, AQO_PLAN_NODE) == 0);

	/* Copy static fields in one command */
	memcpy(new, old, sizeof(AQOPlanNode));

	/* These lists couldn't contain AQO nodes. Use basic machinery */
	new->relids = copyObject(old->relids);
	new->clauses = copyObject(old->clauses);
	new->grouping_exprs = copyObject(old->grouping_exprs);
	new->selectivities = copyObject(old->selectivities);
	enew = (ExtensibleNode *) new;
}

static bool
AQOnodeEqual(const struct ExtensibleNode *a, const struct ExtensibleNode *b)
{
	return false;
}

#define WRITE_INT_FIELD(fldname) \
	appendStringInfo(str, " :" CppAsString(fldname) " %d", node->fldname)

/* Write a boolean field */
#define WRITE_BOOL_FIELD(fldname) \
	appendStringInfo(str, " :" CppAsString(fldname) " %s", \
					 booltostr(node->fldname))

#define WRITE_NODE_FIELD(fldname) \
	(appendStringInfoString(str, " :" CppAsString(fldname) " "), \
	 outNode(str, node->fldname))

/* Write an enumerated-type field as an integer code */
#define WRITE_ENUM_FIELD(fldname, enumtype) \
	appendStringInfo(str, " :" CppAsString(fldname) " %d", \
					 (int) node->fldname)

/* Write a float field --- caller must give format to define precision */
#define WRITE_FLOAT_FIELD(fldname,format) \
	appendStringInfo(str, " :" CppAsString(fldname) " " format, node->fldname)

static void
AQOnodeOut(struct StringInfoData *str, const struct ExtensibleNode *enode)
{
	AQOPlanNode *node = (AQOPlanNode *) enode;

	Assert(0);
	WRITE_BOOL_FIELD(had_path);
	WRITE_NODE_FIELD(relids);
	WRITE_NODE_FIELD(clauses);
	WRITE_NODE_FIELD(selectivities);
	WRITE_NODE_FIELD(grouping_exprs);

	WRITE_ENUM_FIELD(jointype, JoinType);
	WRITE_INT_FIELD(parallel_divisor);
	WRITE_BOOL_FIELD(was_parametrized);

	/* For Adaptive optimization DEBUG purposes */
	WRITE_INT_FIELD(fss);
	WRITE_FLOAT_FIELD(prediction, "%.0f");
}

/* Read an integer field (anything written as ":fldname %d") */
#define READ_INT_FIELD(fldname) \
	token = pg_strtok(&length);		/* skip :fldname */ \
	token = pg_strtok(&length);		/* get field value */ \
	local_node->fldname = atoi(token)

/* Read an enumerated-type field that was written as an integer code */
#define READ_ENUM_FIELD(fldname, enumtype) \
	token = pg_strtok(&length);		/* skip :fldname */ \
	token = pg_strtok(&length);		/* get field value */ \
	local_node->fldname = (enumtype) atoi(token)

/* Read a float field */
#define READ_FLOAT_FIELD(fldname) \
	token = pg_strtok(&length);		/* skip :fldname */ \
	token = pg_strtok(&length);		/* get field value */ \
	local_node->fldname = atof(token)

/* Read a boolean field */
#define READ_BOOL_FIELD(fldname) \
	token = pg_strtok(&length);		/* skip :fldname */ \
	token = pg_strtok(&length);		/* get field value */ \
	local_node->fldname = strtobool(token)

/* Read a Node field */
#define READ_NODE_FIELD(fldname) \
	token = pg_strtok(&length);		/* skip :fldname */ \
	(void) token;				/* in case not used elsewhere */ \
	local_node->fldname = nodeRead(NULL, 0)

static void
AQOnodeRead(struct ExtensibleNode *enode)
{
	AQOPlanNode *local_node = (AQOPlanNode *) enode;
	const char	*token;
	int			length;

	Assert(0);
	READ_BOOL_FIELD(had_path);
	READ_NODE_FIELD(relids);
	READ_NODE_FIELD(clauses);
	READ_NODE_FIELD(selectivities);
	READ_NODE_FIELD(grouping_exprs);

	READ_ENUM_FIELD(jointype, JoinType);
	READ_INT_FIELD(parallel_divisor);
	READ_BOOL_FIELD(was_parametrized);

	/* For Adaptive optimization DEBUG purposes */
	READ_INT_FIELD(fss);
	READ_FLOAT_FIELD(prediction);
}

static const ExtensibleNodeMethods method =
{
	.extnodename = AQO_PLAN_NODE,
	.node_size = sizeof(AQOPlanNode),
	.nodeCopy =  AQOnodeCopy,
	.nodeEqual = AQOnodeEqual,
	.nodeOut = AQOnodeOut,
	.nodeRead = AQOnodeRead
};

void
RegisterAQOPlanNodeMethods(void)
{
	RegisterExtensibleNodeMethods(&method);
}

/*
 * Hook for create_upper_paths_hook
 *
 * Assume, that we are last in the chain of path creators.
 */
void
aqo_store_upper_signature_hook(PlannerInfo *root,
							   UpperRelationKind stage,
							   RelOptInfo *input_rel,
							   RelOptInfo *output_rel,
							   void *extra)
{
	A_Const	*fss_node = makeNode(A_Const);
	List	*relids;
	List	*clauses;
	List	*selectivities;

	if (prev_create_upper_paths_hook)
		(*prev_create_upper_paths_hook)(root, stage, input_rel, output_rel, extra);

	if (!query_context.use_aqo && !query_context.learn_aqo && !force_collect_stat)
		/* Includes 'disabled query' state. */
		return;

	if (stage != UPPERREL_FINAL)
		return;

	set_cheapest(input_rel);
	clauses = get_path_clauses(input_rel->cheapest_total_path,
													root, &selectivities);
	relids = get_list_of_relids(root, input_rel->relids);
	fss_node->val.ival.type = T_Integer;
	fss_node->location = -1;
	fss_node->val.ival.val = get_fss_for_object(relids, clauses, NIL, NULL, NULL);
	output_rel->private = lappend(output_rel->private, (void *) fss_node);
}