queryjumble.c

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/*-------------------------------------------------------------------------
 *
 * queryjumble.c
 *   Query normalization and fingerprinting.
 *
 * Normalization is a process whereby similar queries, typically differing only
 * in their constants (though the exact rules are somewhat more subtle than
 * that) are recognized as equivalent, and are tracked as a single entry.  This
 * is particularly useful for non-prepared queries.
 *
 * Normalization is implemented by fingerprinting queries, selectively
 * serializing those fields of each query tree's nodes that are judged to be
 * essential to the query.  This is referred to as a query jumble.  This is
 * distinct from a regular serialization in that various extraneous
 * information is ignored as irrelevant or not essential to the query, such
 * as the collations of Vars and, most notably, the values of constants.
 *
 * This jumble is acquired at the end of parse analysis of each query, and
 * a 64-bit hash of it is stored into the query's Query.queryId field.
 * The server then copies this value around, making it available in plan
 * tree(s) generated from the query.  The executor can then use this value
 * to blame query costs on the proper queryId.
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/misc/queryjumble.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "common/hashfn.h"
#include "miscadmin.h"
#include "parser/scansup.h"
#include "utils/queryjumble.h"

#define JUMBLE_SIZE             1024    /* query serialization buffer size */

static uint64 compute_utility_query_id(const char *str, int query_location, int query_len);
static void AppendJumble(JumbleState *jstate,
                         const unsigned char *item, Size size);
static void JumbleQueryInternal(JumbleState *jstate, Query *query);
static void JumbleRangeTable(JumbleState *jstate, List *rtable);
static void JumbleRowMarks(JumbleState *jstate, List *rowMarks);
static void JumbleExpr(JumbleState *jstate, Node *node);
static void RecordConstLocation(JumbleState *jstate, int location);

/*
 * Given a possibly multi-statement source string, confine our attention to the
 * relevant part of the string.
 */
const char *
CleanQuerytext(const char *query, int *location, int *len)
{
    int         query_location = *location;
    int         query_len = *len;

    /* First apply starting offset, unless it's -1 (unknown). */
    if (query_location >= 0)
    {
        Assert(query_location <= strlen(query));
        query += query_location;
        /* Length of 0 (or -1) means "rest of string" */
        if (query_len <= 0)
            query_len = strlen(query);
        else
            Assert(query_len <= strlen(query));
    }
    else
    {
        /* If query location is unknown, distrust query_len as well */
        query_location = 0;
        query_len = strlen(query);
    }

    /*
     * Discard leading and trailing whitespace, too.  Use scanner_isspace()
     * not libc's isspace(), because we want to match the lexer's behavior.
     */
    while (query_len > 0 && scanner_isspace(query[0]))
        query++, query_location++, query_len--;
    while (query_len > 0 && scanner_isspace(query[query_len - 1]))
        query_len--;

    *location = query_location;
    *len = query_len;

    return query;
}

JumbleState *
JumbleQuery(Query *query, const char *querytext)
{
    JumbleState *jstate = NULL;

    if (query->utilityStmt)
    {
        query->queryId = compute_utility_query_id(querytext,
                                                  query->stmt_location,
                                                  query->stmt_len);
    }
    else
    {
        jstate = (JumbleState *) palloc(sizeof(JumbleState));

        /* Set up workspace for query jumbling */
        jstate->jumble = (unsigned char *) palloc(JUMBLE_SIZE);
        jstate->jumble_len = 0;
        jstate->clocations_buf_size = 32;
        jstate->clocations = (LocationLen *)
            palloc(jstate->clocations_buf_size * sizeof(LocationLen));
        jstate->clocations_count = 0;
        jstate->highest_extern_param_id = 0;

        /* Compute query ID and mark the Query node with it */
        JumbleQueryInternal(jstate, query);
        query->queryId = DatumGetUInt64(hash_any_extended(jstate->jumble,
                                                          jstate->jumble_len,
                                                          0));

        /*
         * If we are unlucky enough to get a hash of zero, use 1 instead, to
         * prevent confusion with the utility-statement case.
         */
        if (query->queryId == UINT64CONST(0))
            query->queryId = UINT64CONST(1);
    }

    return jstate;
}

/*
 * Compute a query identifier for the given utility query string.
 */
static uint64
compute_utility_query_id(const char *query_text, int query_location, int query_len)
{
    uint64      queryId;
    const char *sql;

    /*
     * Confine our attention to the relevant part of the string, if the query
     * is a portion of a multi-statement source string.
     */
    sql = CleanQuerytext(query_text, &query_location, &query_len);

    queryId = DatumGetUInt64(hash_any_extended((const unsigned char *) sql,
                                               query_len, 0));

    /*
     * If we are unlucky enough to get a hash of zero(invalid), use queryID as
     * 2 instead, queryID 1 is already in use for normal statements.
     */
    if (queryId == UINT64CONST(0))
        queryId = UINT64CONST(2);

    return queryId;
}

/*
 * AppendJumble: Append a value that is substantive in a given query to
 * the current jumble.
 */
static void
AppendJumble(JumbleState *jstate, const unsigned char *item, Size size)
{
    unsigned char *jumble = jstate->jumble;
    Size        jumble_len = jstate->jumble_len;

    /*
     * Whenever the jumble buffer is full, we hash the current contents and
     * reset the buffer to contain just that hash value, thus relying on the
     * hash to summarize everything so far.
     */
    while (size > 0)
    {
        Size        part_size;

        if (jumble_len >= JUMBLE_SIZE)
        {
            uint64      start_hash;

            start_hash = DatumGetUInt64(hash_any_extended(jumble,
                                                          JUMBLE_SIZE, 0));
            memcpy(jumble, &start_hash, sizeof(start_hash));
            jumble_len = sizeof(start_hash);
        }
        part_size = Min(size, JUMBLE_SIZE - jumble_len);
        memcpy(jumble + jumble_len, item, part_size);
        jumble_len += part_size;
        item += part_size;
        size -= part_size;
    }
    jstate->jumble_len = jumble_len;
}

/*
 * Wrappers around AppendJumble to encapsulate details of serialization
 * of individual local variable elements.
 */
#define APP_JUMB(item) \
    AppendJumble(jstate, (const unsigned char *) &(item), sizeof(item))
#define APP_JUMB_STRING(str) \
    AppendJumble(jstate, (const unsigned char *) (str), strlen(str) + 1)

/*
 * JumbleQueryInternal: Selectively serialize the query tree, appending
 * significant data to the "query jumble" while ignoring nonsignificant data.
 *
 * Rule of thumb for what to include is that we should ignore anything not
 * semantically significant (such as alias names) as well as anything that can
 * be deduced from child nodes (else we'd just be double-hashing that piece
 * of information).
 */
static void
JumbleQueryInternal(JumbleState *jstate, Query *query)
{
    Assert(IsA(query, Query));
    Assert(query->utilityStmt == NULL);

    APP_JUMB(query->commandType);
    /* resultRelation is usually predictable from commandType */
    JumbleExpr(jstate, (Node *) query->cteList);
    JumbleRangeTable(jstate, query->rtable);
    JumbleExpr(jstate, (Node *) query->jointree);
    JumbleExpr(jstate, (Node *) query->targetList);
    JumbleExpr(jstate, (Node *) query->onConflict);
    JumbleExpr(jstate, (Node *) query->returningList);
    JumbleExpr(jstate, (Node *) query->groupClause);
    APP_JUMB(query->groupDistinct);
    JumbleExpr(jstate, (Node *) query->groupingSets);
    JumbleExpr(jstate, query->havingQual);
    JumbleExpr(jstate, (Node *) query->windowClause);
    JumbleExpr(jstate, (Node *) query->distinctClause);
    JumbleExpr(jstate, (Node *) query->sortClause);
    JumbleExpr(jstate, query->limitOffset);
    JumbleExpr(jstate, query->limitCount);
    APP_JUMB(query->limitOption);
    JumbleRowMarks(jstate, query->rowMarks);
    JumbleExpr(jstate, query->setOperations);
}

/*
 * Jumble a range table
 */
static void
JumbleRangeTable(JumbleState *jstate, List *rtable)
{
    ListCell   *lc;

    foreach(lc, rtable)
    {
        RangeTblEntry *rte = lfirst_node(RangeTblEntry, lc);

        APP_JUMB(rte->rtekind);
        switch (rte->rtekind)
        {
            case RTE_RELATION:
                APP_JUMB(rte->relid);
                JumbleExpr(jstate, (Node *) rte->tablesample);
                APP_JUMB(rte->inh);
                break;
            case RTE_SUBQUERY:
                JumbleQueryInternal(jstate, rte->subquery);
                break;
            case RTE_JOIN:
                APP_JUMB(rte->jointype);
                break;
            case RTE_FUNCTION:
                JumbleExpr(jstate, (Node *) rte->functions);
                break;
            case RTE_TABLEFUNC:
                JumbleExpr(jstate, (Node *) rte->tablefunc);
                break;
            case RTE_VALUES:
                JumbleExpr(jstate, (Node *) rte->values_lists);
                break;
            case RTE_CTE:

                /*
                 * Depending on the CTE name here isn't ideal, but it's the
                 * only info we have to identify the referenced WITH item.
                 */
                APP_JUMB_STRING(rte->ctename);
                APP_JUMB(rte->ctelevelsup);
                break;
            case RTE_NAMEDTUPLESTORE:
                APP_JUMB_STRING(rte->enrname);
                break;
            case RTE_RESULT:
                break;
            default:
                elog(ERROR, "unrecognized RTE kind: %d", (int) rte->rtekind);
                break;
        }
    }
}

/*
 * Jumble a rowMarks list
 */
static void
JumbleRowMarks(JumbleState *jstate, List *rowMarks)
{
    ListCell   *lc;

    foreach(lc, rowMarks)
    {
        RowMarkClause *rowmark = lfirst_node(RowMarkClause, lc);

        if (!rowmark->pushedDown)
        {
            APP_JUMB(rowmark->rti);
            APP_JUMB(rowmark->strength);
            APP_JUMB(rowmark->waitPolicy);
        }
    }
}

/*
 * Jumble an expression tree
 *
 * In general this function should handle all the same node types that
 * expression_tree_walker() does, and therefore it's coded to be as parallel
 * to that function as possible.  However, since we are only invoked on
 * queries immediately post-parse-analysis, we need not handle node types
 * that only appear in planning.
 *
 * Note: the reason we don't simply use expression_tree_walker() is that the
 * point of that function is to support tree walkers that don't care about
 * most tree node types, but here we care about all types.  We should complain
 * about any unrecognized node type.
 */
static void
JumbleExpr(JumbleState *jstate, Node *node)
{
    ListCell   *temp;

    if (node == NULL)
        return;

    /* Guard against stack overflow due to overly complex expressions */
    check_stack_depth();

    /*
     * We always emit the node's NodeTag, then any additional fields that are
     * considered significant, and then we recurse to any child nodes.
     */
    APP_JUMB(node->type);

    switch (nodeTag(node))
    {
        case T_Var:
            {
                Var        *var = (Var *) node;

                APP_JUMB(var->varno);
                APP_JUMB(var->varattno);
                APP_JUMB(var->varlevelsup);
            }
            break;
        case T_Const:
            {
                Const      *c = (Const *) node;

                /* We jumble only the constant's type, not its value */
                APP_JUMB(c->consttype);
                /* Also, record its parse location for query normalization */
                RecordConstLocation(jstate, c->location);
            }
            break;
        case T_Param:
            {
                Param      *p = (Param *) node;

                APP_JUMB(p->paramkind);
                APP_JUMB(p->paramid);
                APP_JUMB(p->paramtype);
                /* Also, track the highest external Param id */
                if (p->paramkind == PARAM_EXTERN &&
                    p->paramid > jstate->highest_extern_param_id)
                    jstate->highest_extern_param_id = p->paramid;
            }
            break;
        case T_Aggref:
            {
                Aggref     *expr = (Aggref *) node;

                APP_JUMB(expr->aggfnoid);
                JumbleExpr(jstate, (Node *) expr->aggdirectargs);
                JumbleExpr(jstate, (Node *) expr->args);
                JumbleExpr(jstate, (Node *) expr->aggorder);
                JumbleExpr(jstate, (Node *) expr->aggdistinct);
                JumbleExpr(jstate, (Node *) expr->aggfilter);
            }
            break;
        case T_GroupingFunc:
            {
                GroupingFunc *grpnode = (GroupingFunc *) node;

                JumbleExpr(jstate, (Node *) grpnode->refs);
                APP_JUMB(grpnode->agglevelsup);
            }
            break;
        case T_WindowFunc:
            {
                WindowFunc *expr = (WindowFunc *) node;

                APP_JUMB(expr->winfnoid);
                APP_JUMB(expr->winref);
                JumbleExpr(jstate, (Node *) expr->args);
                JumbleExpr(jstate, (Node *) expr->aggfilter);
            }
            break;
        case T_SubscriptingRef:
            {
                SubscriptingRef *sbsref = (SubscriptingRef *) node;

                JumbleExpr(jstate, (Node *) sbsref->refupperindexpr);
                JumbleExpr(jstate, (Node *) sbsref->reflowerindexpr);
                JumbleExpr(jstate, (Node *) sbsref->refexpr);
                JumbleExpr(jstate, (Node *) sbsref->refassgnexpr);
            }
            break;
        case T_FuncExpr:
            {
                FuncExpr   *expr = (FuncExpr *) node;

                APP_JUMB(expr->funcid);
                JumbleExpr(jstate, (Node *) expr->args);
            }
            break;
        case T_NamedArgExpr:
            {
                NamedArgExpr *nae = (NamedArgExpr *) node;

                APP_JUMB(nae->argnumber);
                JumbleExpr(jstate, (Node *) nae->arg);
            }
            break;
        case T_OpExpr:
        case T_DistinctExpr:    /* struct-equivalent to OpExpr */
        case T_NullIfExpr:      /* struct-equivalent to OpExpr */
            {
                OpExpr     *expr = (OpExpr *) node;

                APP_JUMB(expr->opno);
                JumbleExpr(jstate, (Node *) expr->args);
            }
            break;
        case T_ScalarArrayOpExpr:
            {
                ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node;

                APP_JUMB(expr->opno);
                APP_JUMB(expr->useOr);
                JumbleExpr(jstate, (Node *) expr->args);
            }
            break;
        case T_BoolExpr:
            {
                BoolExpr   *expr = (BoolExpr *) node;

                APP_JUMB(expr->boolop);
                JumbleExpr(jstate, (Node *) expr->args);
            }
            break;
        case T_SubLink:
            {
                SubLink    *sublink = (SubLink *) node;

                APP_JUMB(sublink->subLinkType);
                APP_JUMB(sublink->subLinkId);
                JumbleExpr(jstate, (Node *) sublink->testexpr);
                JumbleQueryInternal(jstate, castNode(Query, sublink->subselect));
            }
            break;
        case T_FieldSelect:
            {
                FieldSelect *fs = (FieldSelect *) node;

                APP_JUMB(fs->fieldnum);
                JumbleExpr(jstate, (Node *) fs->arg);
            }
            break;
        case T_FieldStore:
            {
                FieldStore *fstore = (FieldStore *) node;

                JumbleExpr(jstate, (Node *) fstore->arg);
                JumbleExpr(jstate, (Node *) fstore->newvals);
            }
            break;
        case T_RelabelType:
            {
                RelabelType *rt = (RelabelType *) node;

                APP_JUMB(rt->resulttype);
                JumbleExpr(jstate, (Node *) rt->arg);
            }
            break;
        case T_CoerceViaIO:
            {
                CoerceViaIO *cio = (CoerceViaIO *) node;

                APP_JUMB(cio->resulttype);
                JumbleExpr(jstate, (Node *) cio->arg);
            }
            break;
        case T_ArrayCoerceExpr:
            {
                ArrayCoerceExpr *acexpr = (ArrayCoerceExpr *) node;

                APP_JUMB(acexpr->resulttype);
                JumbleExpr(jstate, (Node *) acexpr->arg);
                JumbleExpr(jstate, (Node *) acexpr->elemexpr);
            }
            break;
        case T_ConvertRowtypeExpr:
            {
                ConvertRowtypeExpr *crexpr = (ConvertRowtypeExpr *) node;

                APP_JUMB(crexpr->resulttype);
                JumbleExpr(jstate, (Node *) crexpr->arg);
            }
            break;
        case T_CollateExpr:
            {
                CollateExpr *ce = (CollateExpr *) node;

                APP_JUMB(ce->collOid);
                JumbleExpr(jstate, (Node *) ce->arg);
            }
            break;
        case T_CaseExpr:
            {
                CaseExpr   *caseexpr = (CaseExpr *) node;

                JumbleExpr(jstate, (Node *) caseexpr->arg);
                foreach(temp, caseexpr->args)
                {
                    CaseWhen   *when = lfirst_node(CaseWhen, temp);

                    JumbleExpr(jstate, (Node *) when->expr);
                    JumbleExpr(jstate, (Node *) when->result);
                }
                JumbleExpr(jstate, (Node *) caseexpr->defresult);
            }
            break;
        case T_CaseTestExpr:
            {
                CaseTestExpr *ct = (CaseTestExpr *) node;

                APP_JUMB(ct->typeId);
            }
            break;
        case T_ArrayExpr:
            JumbleExpr(jstate, (Node *) ((ArrayExpr *) node)->elements);
            break;
        case T_RowExpr:
            JumbleExpr(jstate, (Node *) ((RowExpr *) node)->args);
            break;
        case T_RowCompareExpr:
            {
                RowCompareExpr *rcexpr = (RowCompareExpr *) node;

                APP_JUMB(rcexpr->rctype);
                JumbleExpr(jstate, (Node *) rcexpr->largs);
                JumbleExpr(jstate, (Node *) rcexpr->rargs);
            }
            break;
        case T_CoalesceExpr:
            JumbleExpr(jstate, (Node *) ((CoalesceExpr *) node)->args);
            break;
        case T_MinMaxExpr:
            {
                MinMaxExpr *mmexpr = (MinMaxExpr *) node;

                APP_JUMB(mmexpr->op);
                JumbleExpr(jstate, (Node *) mmexpr->args);
            }
            break;
        case T_SQLValueFunction:
            {
                SQLValueFunction *svf = (SQLValueFunction *) node;

                APP_JUMB(svf->op);
                /* type is fully determined by op */
                APP_JUMB(svf->typmod);
            }
            break;
        case T_XmlExpr:
            {
                XmlExpr    *xexpr = (XmlExpr *) node;

                APP_JUMB(xexpr->op);
                JumbleExpr(jstate, (Node *) xexpr->named_args);
                JumbleExpr(jstate, (Node *) xexpr->args);
            }
            break;
        case T_NullTest:
            {
                NullTest   *nt = (NullTest *) node;

                APP_JUMB(nt->nulltesttype);
                JumbleExpr(jstate, (Node *) nt->arg);
            }
            break;
        case T_BooleanTest:
            {
                BooleanTest *bt = (BooleanTest *) node;

                APP_JUMB(bt->booltesttype);
                JumbleExpr(jstate, (Node *) bt->arg);
            }
            break;
        case T_CoerceToDomain:
            {
                CoerceToDomain *cd = (CoerceToDomain *) node;

                APP_JUMB(cd->resulttype);
                JumbleExpr(jstate, (Node *) cd->arg);
            }
            break;
        case T_CoerceToDomainValue:
            {
                CoerceToDomainValue *cdv = (CoerceToDomainValue *) node;

                APP_JUMB(cdv->typeId);
            }
            break;
        case T_SetToDefault:
            {
                SetToDefault *sd = (SetToDefault *) node;

                APP_JUMB(sd->typeId);
            }
            break;
        case T_CurrentOfExpr:
            {
                CurrentOfExpr *ce = (CurrentOfExpr *) node;

                APP_JUMB(ce->cvarno);
                if (ce->cursor_name)
                    APP_JUMB_STRING(ce->cursor_name);
                APP_JUMB(ce->cursor_param);
            }
            break;
        case T_NextValueExpr:
            {
                NextValueExpr *nve = (NextValueExpr *) node;

                APP_JUMB(nve->seqid);
                APP_JUMB(nve->typeId);
            }
            break;
        case T_InferenceElem:
            {
                InferenceElem *ie = (InferenceElem *) node;

                APP_JUMB(ie->infercollid);
                APP_JUMB(ie->inferopclass);
                JumbleExpr(jstate, ie->expr);
            }
            break;
        case T_TargetEntry:
            {
                TargetEntry *tle = (TargetEntry *) node;

                APP_JUMB(tle->resno);
                APP_JUMB(tle->ressortgroupref);
                JumbleExpr(jstate, (Node *) tle->expr);
            }
            break;
        case T_RangeTblRef:
            {
                RangeTblRef *rtr = (RangeTblRef *) node;

                APP_JUMB(rtr->rtindex);
            }
            break;
        case T_JoinExpr:
            {
                JoinExpr   *join = (JoinExpr *) node;

                APP_JUMB(join->jointype);
                APP_JUMB(join->isNatural);
                APP_JUMB(join->rtindex);
                JumbleExpr(jstate, join->larg);
                JumbleExpr(jstate, join->rarg);
                JumbleExpr(jstate, join->quals);
            }
            break;
        case T_FromExpr:
            {
                FromExpr   *from = (FromExpr *) node;

                JumbleExpr(jstate, (Node *) from->fromlist);
                JumbleExpr(jstate, from->quals);
            }
            break;
        case T_OnConflictExpr:
            {
                OnConflictExpr *conf = (OnConflictExpr *) node;

                APP_JUMB(conf->action);
                JumbleExpr(jstate, (Node *) conf->arbiterElems);
                JumbleExpr(jstate, conf->arbiterWhere);
                JumbleExpr(jstate, (Node *) conf->onConflictSet);
                JumbleExpr(jstate, conf->onConflictWhere);
                APP_JUMB(conf->constraint);
                APP_JUMB(conf->exclRelIndex);
                JumbleExpr(jstate, (Node *) conf->exclRelTlist);
            }
            break;
        case T_List:
            foreach(temp, (List *) node)
            {
                JumbleExpr(jstate, (Node *) lfirst(temp));
            }
            break;
        case T_IntList:
            foreach(temp, (List *) node)
            {
                APP_JUMB(lfirst_int(temp));
            }
            break;
        case T_SortGroupClause:
            {
                SortGroupClause *sgc = (SortGroupClause *) node;

                APP_JUMB(sgc->tleSortGroupRef);
                APP_JUMB(sgc->eqop);
                APP_JUMB(sgc->sortop);
                APP_JUMB(sgc->nulls_first);
            }
            break;
        case T_GroupingSet:
            {
                GroupingSet *gsnode = (GroupingSet *) node;

                JumbleExpr(jstate, (Node *) gsnode->content);
            }
            break;
        case T_WindowClause:
            {
                WindowClause *wc = (WindowClause *) node;

                APP_JUMB(wc->winref);
                APP_JUMB(wc->frameOptions);
                JumbleExpr(jstate, (Node *) wc->partitionClause);
                JumbleExpr(jstate, (Node *) wc->orderClause);
                JumbleExpr(jstate, wc->startOffset);
                JumbleExpr(jstate, wc->endOffset);
            }
            break;
        case T_CommonTableExpr:
            {
                CommonTableExpr *cte = (CommonTableExpr *) node;

                /* we store the string name because RTE_CTE RTEs need it */
                APP_JUMB_STRING(cte->ctename);
                APP_JUMB(cte->ctematerialized);
                JumbleQueryInternal(jstate, castNode(Query, cte->ctequery));
            }
            break;
        case T_SetOperationStmt:
            {
                SetOperationStmt *setop = (SetOperationStmt *) node;

                APP_JUMB(setop->op);
                APP_JUMB(setop->all);
                JumbleExpr(jstate, setop->larg);
                JumbleExpr(jstate, setop->rarg);
            }
            break;
        case T_RangeTblFunction:
            {
                RangeTblFunction *rtfunc = (RangeTblFunction *) node;

                JumbleExpr(jstate, rtfunc->funcexpr);
            }
            break;
        case T_TableFunc:
            {
                TableFunc  *tablefunc = (TableFunc *) node;

                JumbleExpr(jstate, tablefunc->docexpr);
                JumbleExpr(jstate, tablefunc->rowexpr);
                JumbleExpr(jstate, (Node *) tablefunc->colexprs);
            }
            break;
        case T_TableSampleClause:
            {
                TableSampleClause *tsc = (TableSampleClause *) node;

                APP_JUMB(tsc->tsmhandler);
                JumbleExpr(jstate, (Node *) tsc->args);
                JumbleExpr(jstate, (Node *) tsc->repeatable);
            }
            break;
        default:
            /* Only a warning, since we can stumble along anyway */
            elog(WARNING, "unrecognized node type: %d",
                 (int) nodeTag(node));
            break;
    }
}

/*
 * Record location of constant within query string of query tree
 * that is currently being walked.
 */
static void
RecordConstLocation(JumbleState *jstate, int location)
{
    /* -1 indicates unknown or undefined location */
    if (location >= 0)
    {
        /* enlarge array if needed */
        if (jstate->clocations_count >= jstate->clocations_buf_size)
        {
            jstate->clocations_buf_size *= 2;
            jstate->clocations = (LocationLen *)
                repalloc(jstate->clocations,
                         jstate->clocations_buf_size *
                         sizeof(LocationLen));
        }
        jstate->clocations[jstate->clocations_count].location = location;
        /* initialize lengths to -1 to simplify third-party module usage */
        jstate->clocations[jstate->clocations_count].length = -1;
        jstate->clocations_count++;
    }
}