/*------------------------------------------------------------------------- * * rewriteSearchCycle.c * Support for rewriting SEARCH and CYCLE clauses. * * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION * src/backend/rewrite/rewriteSearchCycle.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include "catalog/pg_operator_d.h" #include "catalog/pg_type_d.h" #include "nodes/makefuncs.h" #include "nodes/pg_list.h" #include "nodes/parsenodes.h" #include "nodes/primnodes.h" #include "parser/analyze.h" #include "parser/parsetree.h" #include "rewrite/rewriteManip.h" #include "rewrite/rewriteSearchCycle.h" #include "utils/fmgroids.h" /*---------- * Rewrite a CTE with SEARCH or CYCLE clause * * Consider a CTE like * * WITH RECURSIVE ctename (col1, col2, col3) AS ( * query1 * UNION [ALL] * SELECT trosl FROM ctename * ) * * With a search clause * * SEARCH BREADTH FIRST BY col1, col2 SET sqc * * the CTE is rewritten to * * WITH RECURSIVE ctename (col1, col2, col3, sqc) AS ( * SELECT col1, col2, col3, -- original WITH column list * ROW(0, col1, col2) -- initial row of search columns * FROM (query1) "*TLOCRN*" (col1, col2, col3) * UNION [ALL] * SELECT col1, col2, col3, -- same as above * ROW(sqc.depth + 1, col1, col2) -- count depth * FROM (SELECT trosl, ctename.sqc FROM ctename) "*TROCRN*" (col1, col2, col3, sqc) * ) * * (This isn't quite legal SQL: sqc.depth is meant to refer to the first * column of sqc, which has a row type, but the field names are not defined * here. Representing this properly in SQL would be more complicated (and the * SQL standard actually does it in that more complicated way), but the * internal representation allows us to construct it this way.) * * With a search clause * * SEARCH DEPTH FIRST BY col1, col2 SET sqc * * the CTE is rewritten to * * WITH RECURSIVE ctename (col1, col2, col3, sqc) AS ( * SELECT col1, col2, col3, -- original WITH column list * ARRAY[ROW(col1, col2)] -- initial row of search columns * FROM (query1) "*TLOCRN*" (col1, col2, col3) * UNION [ALL] * SELECT col1, col2, col3, -- same as above * sqc || ARRAY[ROW(col1, col2)] -- record rows seen * FROM (SELECT trosl, ctename.sqc FROM ctename) "*TROCRN*" (col1, col2, col3, sqc) * ) * * With a cycle clause * * CYCLE col1, col2 SET cmc TO 'Y' DEFAULT 'N' USING cpa * * (cmc = cycle mark column, cpa = cycle path) the CTE is rewritten to * * WITH RECURSIVE ctename (col1, col2, col3, cmc, cpa) AS ( * SELECT col1, col2, col3, -- original WITH column list * 'N', -- cycle mark default * ARRAY[ROW(col1, col2)] -- initial row of cycle columns * FROM (query1) "*TLOCRN*" (col1, col2, col3) * UNION [ALL] * SELECT col1, col2, col3, -- same as above * CASE WHEN ROW(col1, col2) = ANY (ARRAY[cpa]) THEN 'Y' ELSE 'N' END, -- compute cycle mark column * cpa || ARRAY[ROW(col1, col2)] -- record rows seen * FROM (SELECT trosl, ctename.cmc, ctename.cpa FROM ctename) "*TROCRN*" (col1, col2, col3, cmc, cpa) * WHERE cmc <> 'Y' * ) * * The expression to compute the cycle mark column in the right-hand query is * written as * * CASE WHEN ROW(col1, col2) IN (SELECT p.* FROM TABLE(cpa) p) THEN cmv ELSE cmd END * * in the SQL standard, but in PostgreSQL we can use the scalar-array operator * expression shown above. * * Also, in some of the cases where operators are shown above we actually * directly produce the underlying function call. * * If both a search clause and a cycle clause is specified, then the search * clause column is added before the cycle clause columns. */ /* * Make a RowExpr from the specified column names, which have to be among the * output columns of the CTE. */ static RowExpr * make_path_rowexpr(const CommonTableExpr *cte, const List *col_list) { RowExpr *rowexpr; ListCell *lc; rowexpr = makeNode(RowExpr); rowexpr->row_typeid = RECORDOID; rowexpr->row_format = COERCE_IMPLICIT_CAST; rowexpr->location = -1; foreach(lc, col_list) { char *colname = strVal(lfirst(lc)); for (int i = 0; i < list_length(cte->ctecolnames); i++) { char *colname2 = strVal(list_nth(cte->ctecolnames, i)); if (strcmp(colname, colname2) == 0) { Var *var; var = makeVar(1, i + 1, list_nth_oid(cte->ctecoltypes, i), list_nth_int(cte->ctecoltypmods, i), list_nth_oid(cte->ctecolcollations, i), 0); rowexpr->args = lappend(rowexpr->args, var); rowexpr->colnames = lappend(rowexpr->colnames, makeString(colname)); break; } } } return rowexpr; } /* * Wrap a RowExpr in an ArrayExpr, for the initial search depth first or cycle * row. */ static Expr * make_path_initial_array(RowExpr *rowexpr) { ArrayExpr *arr; arr = makeNode(ArrayExpr); arr->array_typeid = RECORDARRAYOID; arr->element_typeid = RECORDOID; arr->location = -1; arr->elements = list_make1(rowexpr); return (Expr *) arr; } /* * Make an array catenation expression like * * cpa || ARRAY[ROW(cols)] * * where the varattno of cpa is provided as path_varattno. */ static Expr * make_path_cat_expr(RowExpr *rowexpr, AttrNumber path_varattno) { ArrayExpr *arr; FuncExpr *fexpr; arr = makeNode(ArrayExpr); arr->array_typeid = RECORDARRAYOID; arr->element_typeid = RECORDOID; arr->location = -1; arr->elements = list_make1(rowexpr); fexpr = makeFuncExpr(F_ARRAY_CAT, RECORDARRAYOID, list_make2(makeVar(1, path_varattno, RECORDARRAYOID, -1, 0, 0), arr), InvalidOid, InvalidOid, COERCE_EXPLICIT_CALL); return (Expr *) fexpr; } /* * The real work happens here. */ CommonTableExpr * rewriteSearchAndCycle(CommonTableExpr *cte) { Query *ctequery; SetOperationStmt *sos; int rti1, rti2; RangeTblEntry *rte1, *rte2, *newrte; Query *newq1, *newq2; Query *newsubquery; RangeTblRef *rtr; Oid search_seq_type = InvalidOid; AttrNumber sqc_attno = InvalidAttrNumber; AttrNumber cmc_attno = InvalidAttrNumber; AttrNumber cpa_attno = InvalidAttrNumber; TargetEntry *tle; RowExpr *cycle_col_rowexpr = NULL; RowExpr *search_col_rowexpr = NULL; List *ewcl; int cte_rtindex = -1; Assert(cte->search_clause || cte->cycle_clause); cte = copyObject(cte); ctequery = castNode(Query, cte->ctequery); /* * The top level of the CTE's query should be a UNION. Find the two * subqueries. */ Assert(ctequery->setOperations); sos = castNode(SetOperationStmt, ctequery->setOperations); Assert(sos->op == SETOP_UNION); rti1 = castNode(RangeTblRef, sos->larg)->rtindex; rti2 = castNode(RangeTblRef, sos->rarg)->rtindex; rte1 = rt_fetch(rti1, ctequery->rtable); rte2 = rt_fetch(rti2, ctequery->rtable); Assert(rte1->rtekind == RTE_SUBQUERY); Assert(rte2->rtekind == RTE_SUBQUERY); /* * We'll need this a few times later. */ if (cte->search_clause) { if (cte->search_clause->search_breadth_first) search_seq_type = RECORDOID; else search_seq_type = RECORDARRAYOID; } /* * Attribute numbers of the added columns in the CTE's column list */ if (cte->search_clause) sqc_attno = list_length(cte->ctecolnames) + 1; if (cte->cycle_clause) { cmc_attno = list_length(cte->ctecolnames) + 1; cpa_attno = list_length(cte->ctecolnames) + 2; if (cte->search_clause) { cmc_attno++; cpa_attno++; } } /* * Make new left subquery */ newq1 = makeNode(Query); newq1->commandType = CMD_SELECT; newq1->canSetTag = true; newrte = makeNode(RangeTblEntry); newrte->rtekind = RTE_SUBQUERY; newrte->alias = makeAlias("*TLOCRN*", cte->ctecolnames); newrte->eref = newrte->alias; newsubquery = copyObject(rte1->subquery); IncrementVarSublevelsUp((Node *) newsubquery, 1, 1); newrte->subquery = newsubquery; newrte->inFromCl = true; newq1->rtable = list_make1(newrte); rtr = makeNode(RangeTblRef); rtr->rtindex = 1; newq1->jointree = makeFromExpr(list_make1(rtr), NULL); /* * Make target list */ for (int i = 0; i < list_length(cte->ctecolnames); i++) { Var *var; var = makeVar(1, i + 1, list_nth_oid(cte->ctecoltypes, i), list_nth_int(cte->ctecoltypmods, i), list_nth_oid(cte->ctecolcollations, i), 0); tle = makeTargetEntry((Expr *) var, i + 1, strVal(list_nth(cte->ctecolnames, i)), false); tle->resorigtbl = castNode(TargetEntry, list_nth(rte1->subquery->targetList, i))->resorigtbl; tle->resorigcol = castNode(TargetEntry, list_nth(rte1->subquery->targetList, i))->resorigcol; newq1->targetList = lappend(newq1->targetList, tle); } if (cte->search_clause) { Expr *texpr; search_col_rowexpr = make_path_rowexpr(cte, cte->search_clause->search_col_list); if (cte->search_clause->search_breadth_first) { search_col_rowexpr->args = lcons(makeConst(INT8OID, -1, InvalidOid, sizeof(int64), Int64GetDatum(0), false, FLOAT8PASSBYVAL), search_col_rowexpr->args); search_col_rowexpr->colnames = lcons(makeString("*DEPTH*"), search_col_rowexpr->colnames); texpr = (Expr *) search_col_rowexpr; } else texpr = make_path_initial_array(search_col_rowexpr); tle = makeTargetEntry(texpr, list_length(newq1->targetList) + 1, cte->search_clause->search_seq_column, false); newq1->targetList = lappend(newq1->targetList, tle); } if (cte->cycle_clause) { tle = makeTargetEntry((Expr *) cte->cycle_clause->cycle_mark_default, list_length(newq1->targetList) + 1, cte->cycle_clause->cycle_mark_column, false); newq1->targetList = lappend(newq1->targetList, tle); cycle_col_rowexpr = make_path_rowexpr(cte, cte->cycle_clause->cycle_col_list); tle = makeTargetEntry(make_path_initial_array(cycle_col_rowexpr), list_length(newq1->targetList) + 1, cte->cycle_clause->cycle_path_column, false); newq1->targetList = lappend(newq1->targetList, tle); } rte1->subquery = newq1; if (cte->search_clause) { rte1->eref->colnames = lappend(rte1->eref->colnames, makeString(cte->search_clause->search_seq_column)); } if (cte->cycle_clause) { rte1->eref->colnames = lappend(rte1->eref->colnames, makeString(cte->cycle_clause->cycle_mark_column)); rte1->eref->colnames = lappend(rte1->eref->colnames, makeString(cte->cycle_clause->cycle_path_column)); } /* * Make new right subquery */ newq2 = makeNode(Query); newq2->commandType = CMD_SELECT; newq2->canSetTag = true; newrte = makeNode(RangeTblEntry); newrte->rtekind = RTE_SUBQUERY; ewcl = copyObject(cte->ctecolnames); if (cte->search_clause) { ewcl = lappend(ewcl, makeString(cte->search_clause->search_seq_column)); } if (cte->cycle_clause) { ewcl = lappend(ewcl, makeString(cte->cycle_clause->cycle_mark_column)); ewcl = lappend(ewcl, makeString(cte->cycle_clause->cycle_path_column)); } newrte->alias = makeAlias("*TROCRN*", ewcl); newrte->eref = newrte->alias; /* * Find the reference to the recursive CTE in the right UNION subquery's * range table. We expect it to be two levels up from the UNION subquery * (and must check that to avoid being fooled by sub-WITHs with the same * CTE name). There will not be more than one such reference, because the * parser would have rejected that (see checkWellFormedRecursion() in * parse_cte.c). However, the parser doesn't insist that the reference * appear in the UNION subquery's topmost range table, so we might fail to * find it at all. That's an unimplemented case for the moment. */ for (int rti = 1; rti <= list_length(rte2->subquery->rtable); rti++) { RangeTblEntry *e = rt_fetch(rti, rte2->subquery->rtable); if (e->rtekind == RTE_CTE && strcmp(cte->ctename, e->ctename) == 0 && e->ctelevelsup == 2) { cte_rtindex = rti; break; } } if (cte_rtindex <= 0) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("with a SEARCH or CYCLE clause, the recursive reference to WITH query \"%s\" must be at the top level of its right-hand SELECT", cte->ctename))); newsubquery = copyObject(rte2->subquery); IncrementVarSublevelsUp((Node *) newsubquery, 1, 1); /* * Add extra columns to target list of subquery of right subquery */ if (cte->search_clause) { Var *var; /* ctename.sqc */ var = makeVar(cte_rtindex, sqc_attno, search_seq_type, -1, InvalidOid, 0); tle = makeTargetEntry((Expr *) var, list_length(newsubquery->targetList) + 1, cte->search_clause->search_seq_column, false); newsubquery->targetList = lappend(newsubquery->targetList, tle); } if (cte->cycle_clause) { Var *var; /* ctename.cmc */ var = makeVar(cte_rtindex, cmc_attno, cte->cycle_clause->cycle_mark_type, cte->cycle_clause->cycle_mark_typmod, cte->cycle_clause->cycle_mark_collation, 0); tle = makeTargetEntry((Expr *) var, list_length(newsubquery->targetList) + 1, cte->cycle_clause->cycle_mark_column, false); newsubquery->targetList = lappend(newsubquery->targetList, tle); /* ctename.cpa */ var = makeVar(cte_rtindex, cpa_attno, RECORDARRAYOID, -1, InvalidOid, 0); tle = makeTargetEntry((Expr *) var, list_length(newsubquery->targetList) + 1, cte->cycle_clause->cycle_path_column, false); newsubquery->targetList = lappend(newsubquery->targetList, tle); } newrte->subquery = newsubquery; newrte->inFromCl = true; newq2->rtable = list_make1(newrte); rtr = makeNode(RangeTblRef); rtr->rtindex = 1; if (cte->cycle_clause) { Expr *expr; /* * Add cmc <> cmv condition */ expr = make_opclause(cte->cycle_clause->cycle_mark_neop, BOOLOID, false, (Expr *) makeVar(1, cmc_attno, cte->cycle_clause->cycle_mark_type, cte->cycle_clause->cycle_mark_typmod, cte->cycle_clause->cycle_mark_collation, 0), (Expr *) cte->cycle_clause->cycle_mark_value, InvalidOid, cte->cycle_clause->cycle_mark_collation); newq2->jointree = makeFromExpr(list_make1(rtr), (Node *) expr); } else newq2->jointree = makeFromExpr(list_make1(rtr), NULL); /* * Make target list */ for (int i = 0; i < list_length(cte->ctecolnames); i++) { Var *var; var = makeVar(1, i + 1, list_nth_oid(cte->ctecoltypes, i), list_nth_int(cte->ctecoltypmods, i), list_nth_oid(cte->ctecolcollations, i), 0); tle = makeTargetEntry((Expr *) var, i + 1, strVal(list_nth(cte->ctecolnames, i)), false); tle->resorigtbl = castNode(TargetEntry, list_nth(rte2->subquery->targetList, i))->resorigtbl; tle->resorigcol = castNode(TargetEntry, list_nth(rte2->subquery->targetList, i))->resorigcol; newq2->targetList = lappend(newq2->targetList, tle); } if (cte->search_clause) { Expr *texpr; if (cte->search_clause->search_breadth_first) { FieldSelect *fs; FuncExpr *fexpr; /* * ROW(sqc.depth + 1, cols) */ search_col_rowexpr = copyObject(search_col_rowexpr); fs = makeNode(FieldSelect); fs->arg = (Expr *) makeVar(1, sqc_attno, RECORDOID, -1, 0, 0); fs->fieldnum = 1; fs->resulttype = INT8OID; fs->resulttypmod = -1; fexpr = makeFuncExpr(F_INT8INC, INT8OID, list_make1(fs), InvalidOid, InvalidOid, COERCE_EXPLICIT_CALL); lfirst(list_head(search_col_rowexpr->args)) = fexpr; texpr = (Expr *) search_col_rowexpr; } else { /* * sqc || ARRAY[ROW(cols)] */ texpr = make_path_cat_expr(search_col_rowexpr, sqc_attno); } tle = makeTargetEntry(texpr, list_length(newq2->targetList) + 1, cte->search_clause->search_seq_column, false); newq2->targetList = lappend(newq2->targetList, tle); } if (cte->cycle_clause) { ScalarArrayOpExpr *saoe; CaseExpr *caseexpr; CaseWhen *casewhen; /* * CASE WHEN ROW(cols) = ANY (ARRAY[cpa]) THEN cmv ELSE cmd END */ saoe = makeNode(ScalarArrayOpExpr); saoe->location = -1; saoe->opno = RECORD_EQ_OP; saoe->useOr = true; saoe->args = list_make2(cycle_col_rowexpr, makeVar(1, cpa_attno, RECORDARRAYOID, -1, 0, 0)); caseexpr = makeNode(CaseExpr); caseexpr->location = -1; caseexpr->casetype = cte->cycle_clause->cycle_mark_type; caseexpr->casecollid = cte->cycle_clause->cycle_mark_collation; casewhen = makeNode(CaseWhen); casewhen->location = -1; casewhen->expr = (Expr *) saoe; casewhen->result = (Expr *) cte->cycle_clause->cycle_mark_value; caseexpr->args = list_make1(casewhen); caseexpr->defresult = (Expr *) cte->cycle_clause->cycle_mark_default; tle = makeTargetEntry((Expr *) caseexpr, list_length(newq2->targetList) + 1, cte->cycle_clause->cycle_mark_column, false); newq2->targetList = lappend(newq2->targetList, tle); /* * cpa || ARRAY[ROW(cols)] */ tle = makeTargetEntry(make_path_cat_expr(cycle_col_rowexpr, cpa_attno), list_length(newq2->targetList) + 1, cte->cycle_clause->cycle_path_column, false); newq2->targetList = lappend(newq2->targetList, tle); } rte2->subquery = newq2; if (cte->search_clause) { rte2->eref->colnames = lappend(rte2->eref->colnames, makeString(cte->search_clause->search_seq_column)); } if (cte->cycle_clause) { rte2->eref->colnames = lappend(rte2->eref->colnames, makeString(cte->cycle_clause->cycle_mark_column)); rte2->eref->colnames = lappend(rte2->eref->colnames, makeString(cte->cycle_clause->cycle_path_column)); } /* * Add the additional columns to the SetOperationStmt */ if (cte->search_clause) { sos->colTypes = lappend_oid(sos->colTypes, search_seq_type); sos->colTypmods = lappend_int(sos->colTypmods, -1); sos->colCollations = lappend_oid(sos->colCollations, InvalidOid); if (!sos->all) sos->groupClauses = lappend(sos->groupClauses, makeSortGroupClauseForSetOp(search_seq_type, true)); } if (cte->cycle_clause) { sos->colTypes = lappend_oid(sos->colTypes, cte->cycle_clause->cycle_mark_type); sos->colTypmods = lappend_int(sos->colTypmods, cte->cycle_clause->cycle_mark_typmod); sos->colCollations = lappend_oid(sos->colCollations, cte->cycle_clause->cycle_mark_collation); if (!sos->all) sos->groupClauses = lappend(sos->groupClauses, makeSortGroupClauseForSetOp(cte->cycle_clause->cycle_mark_type, true)); sos->colTypes = lappend_oid(sos->colTypes, RECORDARRAYOID); sos->colTypmods = lappend_int(sos->colTypmods, -1); sos->colCollations = lappend_oid(sos->colCollations, InvalidOid); if (!sos->all) sos->groupClauses = lappend(sos->groupClauses, makeSortGroupClauseForSetOp(RECORDARRAYOID, true)); } /* * Add the additional columns to the CTE query's target list */ if (cte->search_clause) { ctequery->targetList = lappend(ctequery->targetList, makeTargetEntry((Expr *) makeVar(1, sqc_attno, search_seq_type, -1, InvalidOid, 0), list_length(ctequery->targetList) + 1, cte->search_clause->search_seq_column, false)); } if (cte->cycle_clause) { ctequery->targetList = lappend(ctequery->targetList, makeTargetEntry((Expr *) makeVar(1, cmc_attno, cte->cycle_clause->cycle_mark_type, cte->cycle_clause->cycle_mark_typmod, cte->cycle_clause->cycle_mark_collation, 0), list_length(ctequery->targetList) + 1, cte->cycle_clause->cycle_mark_column, false)); ctequery->targetList = lappend(ctequery->targetList, makeTargetEntry((Expr *) makeVar(1, cpa_attno, RECORDARRAYOID, -1, InvalidOid, 0), list_length(ctequery->targetList) + 1, cte->cycle_clause->cycle_path_column, false)); } /* * Add the additional columns to the CTE's output columns */ cte->ctecolnames = ewcl; if (cte->search_clause) { cte->ctecoltypes = lappend_oid(cte->ctecoltypes, search_seq_type); cte->ctecoltypmods = lappend_int(cte->ctecoltypmods, -1); cte->ctecolcollations = lappend_oid(cte->ctecolcollations, InvalidOid); } if (cte->cycle_clause) { cte->ctecoltypes = lappend_oid(cte->ctecoltypes, cte->cycle_clause->cycle_mark_type); cte->ctecoltypmods = lappend_int(cte->ctecoltypmods, cte->cycle_clause->cycle_mark_typmod); cte->ctecolcollations = lappend_oid(cte->ctecolcollations, cte->cycle_clause->cycle_mark_collation); cte->ctecoltypes = lappend_oid(cte->ctecoltypes, RECORDARRAYOID); cte->ctecoltypmods = lappend_int(cte->ctecoltypmods, -1); cte->ctecolcollations = lappend_oid(cte->ctecolcollations, InvalidOid); } return cte; }