paramassign.c

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/*-------------------------------------------------------------------------
 *
 * paramassign.c
 *      Functions for assigning PARAM_EXEC slots during planning.
 *
 * This module is responsible for managing three planner data structures:
 *
 * root->glob->paramExecTypes: records actual assignments of PARAM_EXEC slots.
 * The i'th list element holds the data type OID of the i'th parameter slot.
 * (Elements can be InvalidOid if they represent slots that are needed for
 * chgParam signaling, but will never hold a value at runtime.)  This list is
 * global to the whole plan since the executor has only one PARAM_EXEC array.
 * Assignments are permanent for the plan: we never remove entries once added.
 *
 * root->plan_params: a list of PlannerParamItem nodes, recording Vars and
 * PlaceHolderVars that the root's query level needs to supply to lower-level
 * subqueries, along with the PARAM_EXEC number to use for each such value.
 * Elements are added to this list while planning a subquery, and the list
 * is reset to empty after completion of each subquery.
 *
 * root->curOuterParams: a list of NestLoopParam nodes, recording Vars and
 * PlaceHolderVars that some outer level of nestloop needs to pass down to
 * a lower-level plan node in its righthand side.  Elements are added to this
 * list as createplan.c creates lower Plan nodes that need such Params, and
 * are removed when it creates a NestLoop Plan node that will supply those
 * values.
 *
 * The latter two data structures are used to prevent creating multiple
 * PARAM_EXEC slots (each requiring work to fill) when the same upper
 * SubPlan or NestLoop supplies a value that is referenced in more than
 * one place in its child plan nodes.  However, when the same Var has to
 * be supplied to different subplan trees by different SubPlan or NestLoop
 * parent nodes, we don't recognize any commonality; a fresh plan_params or
 * curOuterParams entry will be made (since the old one has been removed
 * when we finished processing the earlier SubPlan or NestLoop) and a fresh
 * PARAM_EXEC number will be assigned.  At one time we tried to avoid
 * allocating duplicate PARAM_EXEC numbers in such cases, but it's harder
 * than it seems to avoid bugs due to overlapping Param lifetimes, so we
 * don't risk that anymore.  Minimizing the number of PARAM_EXEC slots
 * doesn't really save much executor work anyway.
 *
 *
 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/optimizer/util/paramassign.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "nodes/nodeFuncs.h"
#include "nodes/plannodes.h"
#include "optimizer/paramassign.h"
#include "optimizer/placeholder.h"
#include "rewrite/rewriteManip.h"
 
 
/*
 * Select a PARAM_EXEC number to identify the given Var as a parameter for
 * the current subquery.  (It might already have one.)
 * Record the need for the Var in the proper upper-level root->plan_params.
 */
static int
assign_param_for_var(PlannerInfo *root, Var *var)
{
    ListCell   *ppl;
    PlannerParamItem *pitem;
    Index       levelsup;
 
    /* Find the query level the Var belongs to */
    for (levelsup = var->varlevelsup; levelsup > 0; levelsup--)
        root = root->parent_root;
 
    /* If there's already a matching PlannerParamItem there, just use it */
    foreach(ppl, root->plan_params)
    {
        pitem = (PlannerParamItem *) lfirst(ppl);
        if (IsA(pitem->item, Var))
        {
            Var        *pvar = (Var *) pitem->item;
 
            /*
             * This comparison must match _equalVar(), except for ignoring
             * varlevelsup.  Note that _equalVar() ignores varnosyn,
             * varattnosyn, and location, so this does too.
             */
            if (pvar->varno == var->varno &&
                pvar->varattno == var->varattno &&
                pvar->vartype == var->vartype &&
                pvar->vartypmod == var->vartypmod &&
                pvar->varcollid == var->varcollid)
                return pitem->paramId;
        }
    }
 
    /* Nope, so make a new one */
    var = copyObject(var);
    var->varlevelsup = 0;
 
    pitem = makeNode(PlannerParamItem);
    pitem->item = (Node *) var;
    pitem->paramId = list_length(root->glob->paramExecTypes);
    root->glob->paramExecTypes = lappend_oid(root->glob->paramExecTypes,
                                             var->vartype);
 
    root->plan_params = lappend(root->plan_params, pitem);
 
    return pitem->paramId;
}
 
/*
 * Generate a Param node to replace the given Var,
 * which is expected to have varlevelsup > 0 (ie, it is not local).
 * Record the need for the Var in the proper upper-level root->plan_params.
 */
Param *
replace_outer_var(PlannerInfo *root, Var *var)
{
    Param      *retval;
    int         i;
 
    Assert(var->varlevelsup > 0 && var->varlevelsup < root->query_level);
 
    /* Find the Var in the appropriate plan_params, or add it if not present */
    i = assign_param_for_var(root, var);
 
    retval = makeNode(Param);
    retval->paramkind = PARAM_EXEC;
    retval->paramid = i;
    retval->paramtype = var->vartype;
    retval->paramtypmod = var->vartypmod;
    retval->paramcollid = var->varcollid;
    retval->location = var->location;
 
    return retval;
}
 
/*
 * Select a PARAM_EXEC number to identify the given PlaceHolderVar as a
 * parameter for the current subquery.  (It might already have one.)
 * Record the need for the PHV in the proper upper-level root->plan_params.
 *
 * This is just like assign_param_for_var, except for PlaceHolderVars.
 */
static int
assign_param_for_placeholdervar(PlannerInfo *root, PlaceHolderVar *phv)
{
    ListCell   *ppl;
    PlannerParamItem *pitem;
    Index       levelsup;
 
    /* Find the query level the PHV belongs to */
    for (levelsup = phv->phlevelsup; levelsup > 0; levelsup--)
        root = root->parent_root;
 
    /* If there's already a matching PlannerParamItem there, just use it */
    foreach(ppl, root->plan_params)
    {
        pitem = (PlannerParamItem *) lfirst(ppl);
        if (IsA(pitem->item, PlaceHolderVar))
        {
            PlaceHolderVar *pphv = (PlaceHolderVar *) pitem->item;
 
            /* We assume comparing the PHIDs is sufficient */
            if (pphv->phid == phv->phid)
                return pitem->paramId;
        }
    }
 
    /* Nope, so make a new one */
    phv = copyObject(phv);
    IncrementVarSublevelsUp((Node *) phv, -((int) phv->phlevelsup), 0);
    Assert(phv->phlevelsup == 0);
 
    pitem = makeNode(PlannerParamItem);
    pitem->item = (Node *) phv;
    pitem->paramId = list_length(root->glob->paramExecTypes);
    root->glob->paramExecTypes = lappend_oid(root->glob->paramExecTypes,
                                             exprType((Node *) phv->phexpr));
 
    root->plan_params = lappend(root->plan_params, pitem);
 
    return pitem->paramId;
}
 
/*
 * Generate a Param node to replace the given PlaceHolderVar,
 * which is expected to have phlevelsup > 0 (ie, it is not local).
 * Record the need for the PHV in the proper upper-level root->plan_params.
 *
 * This is just like replace_outer_var, except for PlaceHolderVars.
 */
Param *
replace_outer_placeholdervar(PlannerInfo *root, PlaceHolderVar *phv)
{
    Param      *retval;
    int         i;
 
    Assert(phv->phlevelsup > 0 && phv->phlevelsup < root->query_level);
 
    /* Find the PHV in the appropriate plan_params, or add it if not present */
    i = assign_param_for_placeholdervar(root, phv);
 
    retval = makeNode(Param);
    retval->paramkind = PARAM_EXEC;
    retval->paramid = i;
    retval->paramtype = exprType((Node *) phv->phexpr);
    retval->paramtypmod = exprTypmod((Node *) phv->phexpr);
    retval->paramcollid = exprCollation((Node *) phv->phexpr);
    retval->location = -1;
 
    return retval;
}
 
/*
 * Generate a Param node to replace the given Aggref
 * which is expected to have agglevelsup > 0 (ie, it is not local).
 * Record the need for the Aggref in the proper upper-level root->plan_params.
 */
Param *
replace_outer_agg(PlannerInfo *root, Aggref *agg)
{
    Param      *retval;
    PlannerParamItem *pitem;
    Index       levelsup;
 
    Assert(agg->agglevelsup > 0 && agg->agglevelsup < root->query_level);
 
    /* Find the query level the Aggref belongs to */
    for (levelsup = agg->agglevelsup; levelsup > 0; levelsup--)
        root = root->parent_root;
 
    /*
     * It does not seem worthwhile to try to de-duplicate references to outer
     * aggs.  Just make a new slot every time.
     */
    agg = copyObject(agg);
    IncrementVarSublevelsUp((Node *) agg, -((int) agg->agglevelsup), 0);
    Assert(agg->agglevelsup == 0);
 
    pitem = makeNode(PlannerParamItem);
    pitem->item = (Node *) agg;
    pitem->paramId = list_length(root->glob->paramExecTypes);
    root->glob->paramExecTypes = lappend_oid(root->glob->paramExecTypes,
                                             agg->aggtype);
 
    root->plan_params = lappend(root->plan_params, pitem);
 
    retval = makeNode(Param);
    retval->paramkind = PARAM_EXEC;
    retval->paramid = pitem->paramId;
    retval->paramtype = agg->aggtype;
    retval->paramtypmod = -1;
    retval->paramcollid = agg->aggcollid;
    retval->location = agg->location;
 
    return retval;
}
 
/*
 * Generate a Param node to replace the given GroupingFunc expression which is
 * expected to have agglevelsup > 0 (ie, it is not local).
 * Record the need for the GroupingFunc in the proper upper-level
 * root->plan_params.
 */
Param *
replace_outer_grouping(PlannerInfo *root, GroupingFunc *grp)
{
    Param      *retval;
    PlannerParamItem *pitem;
    Index       levelsup;
    Oid         ptype = exprType((Node *) grp);
 
    Assert(grp->agglevelsup > 0 && grp->agglevelsup < root->query_level);
 
    /* Find the query level the GroupingFunc belongs to */
    for (levelsup = grp->agglevelsup; levelsup > 0; levelsup--)
        root = root->parent_root;
 
    /*
     * It does not seem worthwhile to try to de-duplicate references to outer
     * aggs.  Just make a new slot every time.
     */
    grp = copyObject(grp);
    IncrementVarSublevelsUp((Node *) grp, -((int) grp->agglevelsup), 0);
    Assert(grp->agglevelsup == 0);
 
    pitem = makeNode(PlannerParamItem);
    pitem->item = (Node *) grp;
    pitem->paramId = list_length(root->glob->paramExecTypes);
    root->glob->paramExecTypes = lappend_oid(root->glob->paramExecTypes,
                                             ptype);
 
    root->plan_params = lappend(root->plan_params, pitem);
 
    retval = makeNode(Param);
    retval->paramkind = PARAM_EXEC;
    retval->paramid = pitem->paramId;
    retval->paramtype = ptype;
    retval->paramtypmod = -1;
    retval->paramcollid = InvalidOid;
    retval->location = grp->location;
 
    return retval;
}
 
/*
 * Generate a Param node to replace the given Var,
 * which is expected to come from some upper NestLoop plan node.
 * Record the need for the Var in root->curOuterParams.
 */
Param *
replace_nestloop_param_var(PlannerInfo *root, Var *var)
{
    Param      *param;
    NestLoopParam *nlp;
    ListCell   *lc;
 
    /* Is this Var already listed in root->curOuterParams? */
    foreach(lc, root->curOuterParams)
    {
        nlp = (NestLoopParam *) lfirst(lc);
        if (equal(var, nlp->paramval))
        {
            /* Yes, so just make a Param referencing this NLP's slot */
            param = makeNode(Param);
            param->paramkind = PARAM_EXEC;
            param->paramid = nlp->paramno;
            param->paramtype = var->vartype;
            param->paramtypmod = var->vartypmod;
            param->paramcollid = var->varcollid;
            param->location = var->location;
            return param;
        }
    }
 
    /* No, so assign a PARAM_EXEC slot for a new NLP */
    param = generate_new_exec_param(root,
                                    var->vartype,
                                    var->vartypmod,
                                    var->varcollid);
    param->location = var->location;
 
    /* Add it to the list of required NLPs */
    nlp = makeNode(NestLoopParam);
    nlp->paramno = param->paramid;
    nlp->paramval = copyObject(var);
    root->curOuterParams = lappend(root->curOuterParams, nlp);
 
    /* And return the replacement Param */
    return param;
}
 
/*
 * Generate a Param node to replace the given PlaceHolderVar,
 * which is expected to come from some upper NestLoop plan node.
 * Record the need for the PHV in root->curOuterParams.
 *
 * This is just like replace_nestloop_param_var, except for PlaceHolderVars.
 */
Param *
replace_nestloop_param_placeholdervar(PlannerInfo *root, PlaceHolderVar *phv)
{
    Param      *param;
    NestLoopParam *nlp;
    ListCell   *lc;
 
    /* Is this PHV already listed in root->curOuterParams? */
    foreach(lc, root->curOuterParams)
    {
        nlp = (NestLoopParam *) lfirst(lc);
        if (equal(phv, nlp->paramval))
        {
            /* Yes, so just make a Param referencing this NLP's slot */
            param = makeNode(Param);
            param->paramkind = PARAM_EXEC;
            param->paramid = nlp->paramno;
            param->paramtype = exprType((Node *) phv->phexpr);
            param->paramtypmod = exprTypmod((Node *) phv->phexpr);
            param->paramcollid = exprCollation((Node *) phv->phexpr);
            param->location = -1;
            return param;
        }
    }
 
    /* No, so assign a PARAM_EXEC slot for a new NLP */
    param = generate_new_exec_param(root,
                                    exprType((Node *) phv->phexpr),
                                    exprTypmod((Node *) phv->phexpr),
                                    exprCollation((Node *) phv->phexpr));
 
    /* Add it to the list of required NLPs */
    nlp = makeNode(NestLoopParam);
    nlp->paramno = param->paramid;
    nlp->paramval = (Var *) copyObject(phv);
    root->curOuterParams = lappend(root->curOuterParams, nlp);
 
    /* And return the replacement Param */
    return param;
}
 
/*
 * process_subquery_nestloop_params
 *    Handle params of a parameterized subquery that need to be fed
 *    from an outer nestloop.
 *
 * Currently, that would be *all* params that a subquery in FROM has demanded
 * from the current query level, since they must be LATERAL references.
 *
 * subplan_params is a list of PlannerParamItems that we intend to pass to
 * a subquery-in-FROM.  (This was constructed in root->plan_params while
 * planning the subquery, but isn't there anymore when this is called.)
 *
 * The subplan's references to the outer variables are already represented
 * as PARAM_EXEC Params, since that conversion was done by the routines above
 * while planning the subquery.  So we need not modify the subplan or the
 * PlannerParamItems here.  What we do need to do is add entries to
 * root->curOuterParams to signal the parent nestloop plan node that it must
 * provide these values.  This differs from replace_nestloop_param_var in
 * that the PARAM_EXEC slots to use have already been determined.
 *
 * Note that we also use root->curOuterRels as an implicit parameter for
 * sanity checks.
 */
void
process_subquery_nestloop_params(PlannerInfo *root, List *subplan_params)
{
    ListCell   *lc;
 
    foreach(lc, subplan_params)
    {
        PlannerParamItem *pitem = lfirst_node(PlannerParamItem, lc);
 
        if (IsA(pitem->item, Var))
        {
            Var        *var = (Var *) pitem->item;
            NestLoopParam *nlp;
            ListCell   *lc2;
 
            /* If not from a nestloop outer rel, complain */
            if (!bms_is_member(var->varno, root->curOuterRels))
                elog(ERROR, "non-LATERAL parameter required by subquery");
 
            /* Is this param already listed in root->curOuterParams? */
            foreach(lc2, root->curOuterParams)
            {
                nlp = (NestLoopParam *) lfirst(lc2);
                if (nlp->paramno == pitem->paramId)
                {
                    Assert(equal(var, nlp->paramval));
                    /* Present, so nothing to do */
                    break;
                }
            }
            if (lc2 == NULL)
            {
                /* No, so add it */
                nlp = makeNode(NestLoopParam);
                nlp->paramno = pitem->paramId;
                nlp->paramval = copyObject(var);
                root->curOuterParams = lappend(root->curOuterParams, nlp);
            }
        }
        else if (IsA(pitem->item, PlaceHolderVar))
        {
            PlaceHolderVar *phv = (PlaceHolderVar *) pitem->item;
            NestLoopParam *nlp;
            ListCell   *lc2;
 
            /* If not from a nestloop outer rel, complain */
            if (!bms_is_subset(find_placeholder_info(root, phv)->ph_eval_at,
                               root->curOuterRels))
                elog(ERROR, "non-LATERAL parameter required by subquery");
 
            /* Is this param already listed in root->curOuterParams? */
            foreach(lc2, root->curOuterParams)
            {
                nlp = (NestLoopParam *) lfirst(lc2);
                if (nlp->paramno == pitem->paramId)
                {
                    Assert(equal(phv, nlp->paramval));
                    /* Present, so nothing to do */
                    break;
                }
            }
            if (lc2 == NULL)
            {
                /* No, so add it */
                nlp = makeNode(NestLoopParam);
                nlp->paramno = pitem->paramId;
                nlp->paramval = (Var *) copyObject(phv);
                root->curOuterParams = lappend(root->curOuterParams, nlp);
            }
        }
        else
            elog(ERROR, "unexpected type of subquery parameter");
    }
}
 
/*
 * Identify any NestLoopParams that should be supplied by a NestLoop plan
 * node with the specified lefthand rels.  Remove them from the active
 * root->curOuterParams list and return them as the result list.
 *
 * XXX Here we also hack up the returned Vars and PHVs so that they do not
 * contain nullingrel sets exceeding what is available from the outer side.
 * This is needed if we have applied outer join identity 3,
 *      (A leftjoin B on (Pab)) leftjoin C on (Pb*c)
 *      = A leftjoin (B leftjoin C on (Pbc)) on (Pab)
 * and C contains lateral references to B.  It's still safe to apply the
 * identity, but the parser will have created those references in the form
 * "b*" (i.e., with varnullingrels listing the A/B join), while what we will
 * have available from the nestloop's outer side is just "b".  We deal with
 * that here by stripping the nullingrels down to what is available from the
 * outer side according to leftrelids.
 *
 * That fixes matters for the case of forward application of identity 3.
 * If the identity was applied in the reverse direction, we will have
 * parameter Vars containing too few nullingrel bits rather than too many.
 * Currently, that causes no problems because setrefs.c applies only a
 * subset check to nullingrels in NestLoopParams, but we'd have to work
 * harder if we ever want to tighten that check.  This is all pretty annoying
 * because it greatly weakens setrefs.c's cross-check, but the alternative
 * seems to be to generate multiple versions of each laterally-parameterized
 * subquery, which'd be unduly expensive.
 */
List *
identify_current_nestloop_params(PlannerInfo *root, Relids leftrelids)
{
    List       *result;
    ListCell   *cell;
 
    result = NIL;
    foreach(cell, root->curOuterParams)
    {
        NestLoopParam *nlp = (NestLoopParam *) lfirst(cell);
 
        /*
         * We are looking for Vars and PHVs that can be supplied by the
         * lefthand rels.  When we find one, it's okay to modify it in-place
         * because all the routines above make a fresh copy to put into
         * curOuterParams.
         */
        if (IsA(nlp->paramval, Var) &&
            bms_is_member(nlp->paramval->varno, leftrelids))
        {
            Var        *var = (Var *) nlp->paramval;
 
            root->curOuterParams = foreach_delete_current(root->curOuterParams,
                                                          cell);
            var->varnullingrels = bms_intersect(var->varnullingrels,
                                                leftrelids);
            result = lappend(result, nlp);
        }
        else if (IsA(nlp->paramval, PlaceHolderVar) &&
                 bms_is_subset(find_placeholder_info(root,
                                                     (PlaceHolderVar *) nlp->paramval)->ph_eval_at,
                               leftrelids))
        {
            PlaceHolderVar *phv = (PlaceHolderVar *) nlp->paramval;
 
            root->curOuterParams = foreach_delete_current(root->curOuterParams,
                                                          cell);
            phv->phnullingrels = bms_intersect(phv->phnullingrels,
                                               leftrelids);
            result = lappend(result, nlp);
        }
    }
    return result;
}
 
/*
 * Generate a new Param node that will not conflict with any other.
 *
 * This is used to create Params representing subplan outputs or
 * NestLoop parameters.
 *
 * We don't need to build a PlannerParamItem for such a Param, but we do
 * need to make sure we record the type in paramExecTypes (otherwise,
 * there won't be a slot allocated for it).
 */
Param *
generate_new_exec_param(PlannerInfo *root, Oid paramtype, int32 paramtypmod,
                        Oid paramcollation)
{
    Param      *retval;
 
    retval = makeNode(Param);
    retval->paramkind = PARAM_EXEC;
    retval->paramid = list_length(root->glob->paramExecTypes);
    root->glob->paramExecTypes = lappend_oid(root->glob->paramExecTypes,
                                             paramtype);
    retval->paramtype = paramtype;
    retval->paramtypmod = paramtypmod;
    retval->paramcollid = paramcollation;
    retval->location = -1;
 
    return retval;
}
 
/*
 * Assign a (nonnegative) PARAM_EXEC ID for a special parameter (one that
 * is not actually used to carry a value at runtime).  Such parameters are
 * used for special runtime signaling purposes, such as connecting a
 * recursive union node to its worktable scan node or forcing plan
 * re-evaluation within the EvalPlanQual mechanism.  No actual Param node
 * exists with this ID, however.
 */
int
assign_special_exec_param(PlannerInfo *root)
{
    int         paramId = list_length(root->glob->paramExecTypes);
 
    root->glob->paramExecTypes = lappend_oid(root->glob->paramExecTypes,
                                             InvalidOid);
    return paramId;
}