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SEARCH and CYCLE clauses
This adds the SQL standard feature that adds the SEARCH and CYCLE clauses to recursive queries to be able to do produce breadth- or depth-first search orders and detect cycles. These clauses can be rewritten into queries using existing syntax, and that is what this patch does in the rewriter. Reviewed-by: Vik Fearing <vik@postgresfriends.org> Reviewed-by: Pavel Stehule <pavel.stehule@gmail.com> Discussion: https://www.postgresql.org/message-id/flat/db80ceee-6f97-9b4a-8ee8-3ba0c58e5be2@2ndquadrant.com
This commit is contained in:
Peter Eisentraut
@ -18,9 +18,13 @@
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#include "catalog/pg_type.h"
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#include "nodes/nodeFuncs.h"
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#include "parser/analyze.h"
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#include "parser/parse_coerce.h"
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#include "parser/parse_collate.h"
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#include "parser/parse_cte.h"
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#include "parser/parse_expr.h"
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#include "utils/builtins.h"
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#include "utils/lsyscache.h"
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#include "utils/typcache.h"
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/* Enumeration of contexts in which a self-reference is disallowed */
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@ -334,6 +338,195 @@ analyzeCTE(ParseState *pstate, CommonTableExpr *cte)
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if (lctyp != NULL || lctypmod != NULL || lccoll != NULL) /* shouldn't happen */
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elog(ERROR, "wrong number of output columns in WITH");
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}
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if (cte->search_clause || cte->cycle_clause)
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{
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Query *ctequery;
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SetOperationStmt *sos;
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if (!cte->cterecursive)
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("WITH query is not recursive"),
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parser_errposition(pstate, cte->location)));
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/*
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* SQL requires a WITH list element (CTE) to be "expandable" in order
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* to allow a search or cycle clause. That is a stronger requirement
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* than just being recursive. It basically means the query expression
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* looks like
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*
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* non-recursive query UNION [ALL] recursive query
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*
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* and that the recursive query is not itself a set operation.
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*
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* As of this writing, most of these criteria are already satisfied by
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* all recursive CTEs allowed by PostgreSQL. In the future, if
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* further variants recursive CTEs are accepted, there might be
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* further checks required here to determine what is "expandable".
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*/
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ctequery = castNode(Query, cte->ctequery);
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Assert(ctequery->setOperations);
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sos = castNode(SetOperationStmt, ctequery->setOperations);
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/*
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* This left side check is not required for expandability, but
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* rewriteSearchAndCycle() doesn't currently have support for it, so
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* we catch it here.
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*/
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if (!IsA(sos->larg, RangeTblRef))
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ereport(ERROR,
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(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
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errmsg("with a SEARCH or CYCLE clause, the left side of the UNION must be a SELECT")));
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if (!IsA(sos->rarg, RangeTblRef))
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("with a SEARCH or CYCLE clause, the right side of the UNION must be a SELECT")));
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}
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if (cte->search_clause)
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{
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ListCell *lc;
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List *seen = NIL;
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foreach(lc, cte->search_clause->search_col_list)
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{
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Value *colname = lfirst(lc);
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if (!list_member(cte->ctecolnames, colname))
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("search column \"%s\" not in WITH query column list",
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strVal(colname)),
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parser_errposition(pstate, cte->search_clause->location)));
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if (list_member(seen, colname))
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ereport(ERROR,
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(errcode(ERRCODE_DUPLICATE_COLUMN),
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errmsg("search column \"%s\" specified more than once",
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strVal(colname)),
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parser_errposition(pstate, cte->search_clause->location)));
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seen = lappend(seen, colname);
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}
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if (list_member(cte->ctecolnames, makeString(cte->search_clause->search_seq_column)))
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ereport(ERROR,
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errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("search sequence column name \"%s\" already used in WITH query column list",
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cte->search_clause->search_seq_column),
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parser_errposition(pstate, cte->search_clause->location));
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}
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if (cte->cycle_clause)
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{
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ListCell *lc;
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List *seen = NIL;
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TypeCacheEntry *typentry;
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Oid op;
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foreach(lc, cte->cycle_clause->cycle_col_list)
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{
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Value *colname = lfirst(lc);
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if (!list_member(cte->ctecolnames, colname))
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("cycle column \"%s\" not in WITH query column list",
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strVal(colname)),
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parser_errposition(pstate, cte->cycle_clause->location)));
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if (list_member(seen, colname))
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ereport(ERROR,
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(errcode(ERRCODE_DUPLICATE_COLUMN),
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errmsg("cycle column \"%s\" specified more than once",
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strVal(colname)),
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parser_errposition(pstate, cte->cycle_clause->location)));
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seen = lappend(seen, colname);
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}
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if (list_member(cte->ctecolnames, makeString(cte->cycle_clause->cycle_mark_column)))
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ereport(ERROR,
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errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("cycle mark column name \"%s\" already used in WITH query column list",
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cte->cycle_clause->cycle_mark_column),
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parser_errposition(pstate, cte->cycle_clause->location));
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cte->cycle_clause->cycle_mark_value = transformExpr(pstate, cte->cycle_clause->cycle_mark_value,
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EXPR_KIND_CYCLE_MARK);
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cte->cycle_clause->cycle_mark_default = transformExpr(pstate, cte->cycle_clause->cycle_mark_default,
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EXPR_KIND_CYCLE_MARK);
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if (list_member(cte->ctecolnames, makeString(cte->cycle_clause->cycle_path_column)))
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ereport(ERROR,
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errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("cycle path column name \"%s\" already used in WITH query column list",
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cte->cycle_clause->cycle_path_column),
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parser_errposition(pstate, cte->cycle_clause->location));
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if (strcmp(cte->cycle_clause->cycle_mark_column,
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cte->cycle_clause->cycle_path_column) == 0)
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ereport(ERROR,
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errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("cycle mark column name and cycle path column name are the same"),
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parser_errposition(pstate, cte->cycle_clause->location));
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cte->cycle_clause->cycle_mark_type = select_common_type(pstate,
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list_make2(cte->cycle_clause->cycle_mark_value,
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cte->cycle_clause->cycle_mark_default),
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"CYCLE", NULL);
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cte->cycle_clause->cycle_mark_value = coerce_to_common_type(pstate,
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cte->cycle_clause->cycle_mark_value,
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cte->cycle_clause->cycle_mark_type,
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"CYCLE/SET/TO");
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cte->cycle_clause->cycle_mark_default = coerce_to_common_type(pstate,
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cte->cycle_clause->cycle_mark_default,
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cte->cycle_clause->cycle_mark_type,
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"CYCLE/SET/DEFAULT");
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cte->cycle_clause->cycle_mark_typmod = select_common_typmod(pstate,
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list_make2(cte->cycle_clause->cycle_mark_value,
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cte->cycle_clause->cycle_mark_default),
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cte->cycle_clause->cycle_mark_type);
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cte->cycle_clause->cycle_mark_collation = select_common_collation(pstate,
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list_make2(cte->cycle_clause->cycle_mark_value,
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cte->cycle_clause->cycle_mark_default),
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true);
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typentry = lookup_type_cache(cte->cycle_clause->cycle_mark_type, TYPECACHE_EQ_OPR);
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if (!typentry->eq_opr)
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ereport(ERROR,
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errcode(ERRCODE_UNDEFINED_FUNCTION),
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errmsg("could not identify an equality operator for type %s",
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format_type_be(cte->cycle_clause->cycle_mark_type)));
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op = get_negator(typentry->eq_opr);
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if (!op)
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ereport(ERROR,
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errcode(ERRCODE_UNDEFINED_FUNCTION),
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errmsg("could not identify an inequality operator for type %s",
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format_type_be(cte->cycle_clause->cycle_mark_type)));
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cte->cycle_clause->cycle_mark_neop = op;
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}
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if (cte->search_clause && cte->cycle_clause)
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{
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if (strcmp(cte->search_clause->search_seq_column,
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cte->cycle_clause->cycle_mark_column) == 0)
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ereport(ERROR,
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errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("search sequence column name and cycle mark column name are the same"),
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parser_errposition(pstate, cte->search_clause->location));
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if (strcmp(cte->search_clause->search_seq_column,
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cte->cycle_clause->cycle_path_column) == 0)
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ereport(ERROR,
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errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("search_sequence column name and cycle path column name are the same"),
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parser_errposition(pstate, cte->search_clause->location));
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}
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}
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/*
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