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deparse.c
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/*-------------------------------------------------------------------------
*
* deparse.c
* Query deparser for postgres_fdw
*
* This file includes functions that examine query WHERE clauses to see
* whether they're safe to send to the remote server for execution, as
* well as functions to construct the query text to be sent. The latter
* functionality is annoyingly duplicative of ruleutils.c, but there are
* enough special considerations that it seems best to keep this separate.
* One saving grace is that we only need deparse logic for node types that
* we consider safe to send.
*
* We assume that the remote session's search_path is exactly "pg_catalog",
* and thus we need schema-qualify all and only names outside pg_catalog.
*
* Portions Copyright (c) 2012-2017, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/postgres_fdw/deparse.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "vops_fdw.h"
#include "access/heapam.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "catalog/pg_aggregate.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_type.h"
#include "commands/defrem.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "nodes/plannodes.h"
#include "optimizer/clauses.h"
#include "optimizer/prep.h"
#include "optimizer/tlist.h"
#if PG_VERSION_NUM>=120000
#include "optimizer/optimizer.h"
#else
#include "optimizer/var.h"
#endif
#include "parser/parsetree.h"
#include "utils/builtins.h"
#include "utils/hsearch.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/syscache.h"
#include "utils/typcache.h"
#include "vops.h"
/*
* Global context for foreign_expr_walker's search of an expression tree.
*/
typedef struct foreign_glob_cxt
{
PlannerInfo *root; /* global planner state */
RelOptInfo *foreignrel; /* the foreign relation we are planning for */
Relids relids; /* relids of base relations in the underlying
* scan */
} foreign_glob_cxt;
/*
* Context for deparseExpr
*/
typedef struct deparse_expr_cxt
{
PlannerInfo *root; /* global planner state */
RelOptInfo *foreignrel; /* the foreign relation we are planning for */
RelOptInfo *scanrel; /* the underlying scan relation. Same as
* foreignrel, when that represents a join or
* a base relation. */
StringInfo buf; /* output buffer to append to */
List **params_list; /* exprs that will become remote Params */
} deparse_expr_cxt;
#define REL_ALIAS_PREFIX "r"
/* Handy macro to add relation name qualification */
#define ADD_REL_QUALIFIER(buf, varno) \
appendStringInfo((buf), "%s%d.", REL_ALIAS_PREFIX, (varno))
/*
* Functions to determine whether an expression can be evaluated safely on
* remote server.
*/
static bool foreign_expr_walker(Node *node,
foreign_glob_cxt *glob_cxt);
static void
deparseStringLiteral(StringInfo buf, const char *val);
/*
* Functions to construct string representation of a node tree.
*/
static void deparseTargetList(StringInfo buf,
PlannerInfo *root,
Index rtindex,
Relation rel,
bool is_returning,
Bitmapset *attrs_used,
bool qualify_col,
List **retrieved_attrs);
static void deparseExplicitTargetList(List *tlist, List **retrieved_attrs,
deparse_expr_cxt *context);
static void deparseColumnRef(StringInfo buf, int varno, int varattno,
PlannerInfo *root, bool qualify_col);
static void deparseExpr(Expr *expr, deparse_expr_cxt *context);
static void deparseVar(Var *node, deparse_expr_cxt *context);
static void deparseConst(Const *node, deparse_expr_cxt *context, int showtype);
static void deparseParam(Param *node, deparse_expr_cxt *context);
#if PG_VERSION_NUM>=120000
static void deparseSubscriptingRef(SubscriptingRef *node, deparse_expr_cxt *context);
#else
static void deparseArrayRef(ArrayRef *node, deparse_expr_cxt *context);
#endif
static void deparseFuncExpr(FuncExpr *node, deparse_expr_cxt *context);
static void deparseOpExpr(OpExpr *node, deparse_expr_cxt *context);
static void deparseOperatorName(StringInfo buf, Form_pg_operator opform);
static void deparseDistinctExpr(DistinctExpr *node, deparse_expr_cxt *context);
static void deparseScalarArrayOpExpr(ScalarArrayOpExpr *node,
deparse_expr_cxt *context);
static void deparseRelabelType(RelabelType *node, deparse_expr_cxt *context);
static void deparseBoolExpr(BoolExpr *node, deparse_expr_cxt *context);
static void deparseNullTest(NullTest *node, deparse_expr_cxt *context);
static void deparseArrayExpr(ArrayExpr *node, deparse_expr_cxt *context);
static void printRemoteParam(int paramindex, Oid paramtype, int32 paramtypmod,
deparse_expr_cxt *context);
static void printRemotePlaceholder(Oid paramtype, int32 paramtypmod,
deparse_expr_cxt *context);
static void deparseSelectSql(List *tlist, List **retrieved_attrs,
deparse_expr_cxt *context);
static void deparseLockingClause(deparse_expr_cxt *context);
static void appendConditions(List *exprs, deparse_expr_cxt *context);
static void deparseFromExprForRel(StringInfo buf, PlannerInfo *root,
RelOptInfo *joinrel, bool use_alias, List **params_list);
static void deparseFromExpr(List *quals, deparse_expr_cxt *context);
static void deparseAggref(Aggref *node, deparse_expr_cxt *context);
static void appendGroupByClause(List *tlist, deparse_expr_cxt *context);
static void appendAggOrderBy(List *orderList, List *targetList,
deparse_expr_cxt *context);
static void appendFunctionName(Oid funcid, deparse_expr_cxt *context);
static Node *deparseSortGroupClause(Index ref, List *tlist,
deparse_expr_cxt *context);
/*
* Examine each qual clause in input_conds, and classify them into two groups,
* which are returned as two lists:
* - remote_conds contains expressions that can be evaluated remotely
* - local_conds contains expressions that can't be evaluated remotely
*/
void
vopsClassifyConditions(PlannerInfo *root,
RelOptInfo *baserel,
List *input_conds,
List **remote_conds,
List **local_conds)
{
ListCell *lc;
*remote_conds = NIL;
*local_conds = NIL;
foreach(lc, input_conds)
{
RestrictInfo *ri = (RestrictInfo *) lfirst(lc);
if (vops_is_foreign_expr(root, baserel, ri->clause))
*remote_conds = lappend(*remote_conds, ri);
else
*local_conds = lappend(*local_conds, ri);
}
}
/*
* Returns true if given expr is safe to evaluate on the foreign server.
*/
bool
vops_is_foreign_expr(PlannerInfo *root,
RelOptInfo *baserel,
Expr *expr)
{
foreign_glob_cxt glob_cxt;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) (baserel->fdw_private);
/*
* Check that the expression consists of nodes that are safe to execute
* remotely.
*/
glob_cxt.root = root;
glob_cxt.foreignrel = baserel;
/*
* For an upper relation, use relids from its underneath scan relation,
* because the upperrel's own relids currently aren't set to anything
* meaningful by the core code. For other relation, use their own relids.
*/
if (baserel->reloptkind == RELOPT_UPPER_REL)
glob_cxt.relids = fpinfo->upperrel->relids;
else
glob_cxt.relids = baserel->relids;
if (!foreign_expr_walker((Node *) expr, &glob_cxt))
return false;
/* OK to evaluate on the remote server */
return true;
}
/*
* Check if expression is safe to execute remotely, and return true if so.
*/
static bool
foreign_expr_walker(Node *node,
foreign_glob_cxt *glob_cxt)
{
PgFdwRelationInfo *fpinfo;
/* Need do nothing for empty subexpressions */
if (node == NULL)
return true;
/* May need server info from baserel's fdw_private struct */
fpinfo = (PgFdwRelationInfo *) (glob_cxt->foreignrel->fdw_private);
switch (nodeTag(node))
{
case T_Var:
{
Var *var = (Var *) node;
/* If the Var is from the foreign table */
if (bms_is_member(var->varno, glob_cxt->relids) &&
var->varlevelsup == 0)
{
if (var->varattno <= 0 || !bms_is_member(var->varattno - FirstLowInvalidHeapAttributeNumber, fpinfo->vops_attrs))
{
return false;
}
} else {
return false;
}
break;
}
case T_Const:
case T_Param:
break;
#if PG_VERSION_NUM>=120000
case T_SubscriptingRef:
{
SubscriptingRef *ar = (SubscriptingRef *) node;
#else
case T_ArrayRef:
{
ArrayRef *ar = (ArrayRef *) node;
#endif
/* Assignment should not be in restrictions. */
if (ar->refassgnexpr != NULL)
return false;
/*
* Recurse to remaining subexpressions.
*/
if (!foreign_expr_walker((Node *) ar->refupperindexpr,
glob_cxt))
return false;
if (!foreign_expr_walker((Node *) ar->reflowerindexpr,
glob_cxt))
return false;
if (!foreign_expr_walker((Node *) ar->refexpr,
glob_cxt))
return false;
}
break;
case T_FuncExpr:
{
FuncExpr *fe = (FuncExpr *) node;
/*
* Recurse to input subexpressions.
*/
if (!foreign_expr_walker((Node *) fe->args,
glob_cxt))
return false;
}
break;
case T_OpExpr:
{
OpExpr *oe = (OpExpr *) node;
/* TODO: check here if operator is supported by VOPS */
if (!foreign_expr_walker((Node *) oe->args, glob_cxt))
return false;
break;
}
case T_DistinctExpr: /* struct-equivalent to OpExpr */
case T_ScalarArrayOpExpr:
case T_ArrayExpr:
return false;
case T_RelabelType:
{
RelabelType *r = (RelabelType *) node;
if (!foreign_expr_walker((Node *) r->arg, glob_cxt))
return false;
}
break;
case T_BoolExpr:
{
BoolExpr *b = (BoolExpr *) node;
if (!foreign_expr_walker((Node *) b->args, glob_cxt))
return false;
}
break;
case T_NullTest:
{
NullTest *nt = (NullTest *) node;
if (!foreign_expr_walker((Node *) nt->arg, glob_cxt))
return false;
}
break;
case T_List:
{
List *l = (List *) node;
ListCell *lc;
/*
* Recurse to component subexpressions.
*/
foreach(lc, l)
{
if (!foreign_expr_walker((Node *) lfirst(lc), glob_cxt))
return false;
}
}
break;
case T_Aggref:
{
Aggref *agg = (Aggref *) node;
ListCell *lc;
/* Not safe to pushdown when not in grouping context */
if (glob_cxt->foreignrel->reloptkind != RELOPT_UPPER_REL)
return false;
/* Only non-split aggregates are pushable. */
if (agg->aggsplit != AGGSPLIT_SIMPLE)
return false;
/* Ordered aggregates and aggregates with filter are not supported by VOPS */
if (agg->aggorder || agg->aggfilter)
return false;
/*
* Recurse to input args. aggdirectargs, aggorder and
* aggdistinct are all present in args, so no need to check
* their shippability explicitly.
*/
foreach(lc, agg->args)
{
Node *n = (Node *) lfirst(lc);
/* If TargetEntry, extract the expression from it */
if (IsA(n, TargetEntry))
{
TargetEntry *tle = (TargetEntry *) n;
n = (Node *) tle->expr;
}
if (!foreign_expr_walker(n, glob_cxt))
return false;
}
}
break;
default:
/*
* If it's anything else, assume it's unsafe. This list can be
* expanded later, but don't forget to add deparse support below.
*/
return false;
}
/* It looks OK */
return true;
}
/*
* Convert type OID + typmod info into a type name we can ship to the remote
* server. Someplace else had better have verified that this type name is
* expected to be known on the remote end.
*
* This is almost just format_type_with_typemod(), except that if left to its
* own devices, that function will make schema-qualification decisions based
* on the local search_path, which is wrong. We must schema-qualify all
* type names that are not in pg_catalog. We assume here that built-in types
* are all in pg_catalog and need not be qualified; otherwise, qualify.
*/
char *
vops_deparse_type_name(Oid type_oid, int32 typemod)
{
#if PG_VERSION_NUM>=110000
uint8 flags = FORMAT_TYPE_TYPEMOD_GIVEN;
#if PG_VERSION_NUM>=140000
if (type_oid >= FirstGenbkiObjectId)
#else
if (type_oid >= FirstBootstrapObjectId)
#endif
flags |= FORMAT_TYPE_FORCE_QUALIFY;
return format_type_extended(type_oid, typemod, flags);
#else
if (type_oid < FirstBootstrapObjectId)
return format_type_with_typemod(type_oid, typemod);
else
return format_type_with_typemod_qualified(type_oid, typemod);
#endif
}
/*
* Build the targetlist for given relation to be deparsed as SELECT clause.
*
* The output targetlist contains the columns that need to be fetched from the
* foreign server for the given relation. If foreignrel is an upper relation,
* then the output targetlist can also contain expressions to be evaluated on
* foreign server.
*/
List *
vops_build_tlist_to_deparse(RelOptInfo *foreignrel)
{
List *tlist = NIL;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) foreignrel->fdw_private;
/*
* For an upper relation, we have already built the target list while
* checking shippability, so just return that.
*/
if (foreignrel->reloptkind == RELOPT_UPPER_REL)
return fpinfo->grouped_tlist;
/*
* We require columns specified in foreignrel->reltarget->exprs and those
* required for evaluating the local conditions.
*/
tlist = add_to_flat_tlist(tlist,
pull_var_clause((Node *) foreignrel->reltarget->exprs,
PVC_RECURSE_PLACEHOLDERS));
tlist = add_to_flat_tlist(tlist,
pull_var_clause((Node *) fpinfo->local_conds,
PVC_RECURSE_PLACEHOLDERS));
return tlist;
}
/*
* Deparse SELECT statement for given relation into buf.
*
* tlist contains the list of desired columns to be fetched from foreign server.
* For a base relation fpinfo->attrs_used is used to construct SELECT clause,
* hence the tlist is ignored for a base relation.
*
* remote_conds is the list of conditions to be deparsed into the WHERE clause
* (or, in the case of upper relations, into the HAVING clause).
*
* If params_list is not NULL, it receives a list of Params and other-relation
* Vars used in the clauses; these values must be transmitted to the remote
* server as parameter values.
*
* If params_list is NULL, we're generating the query for EXPLAIN purposes,
* so Params and other-relation Vars should be replaced by dummy values.
*
* pathkeys is the list of pathkeys to order the result by.
*
* List of columns selected is returned in retrieved_attrs.
*/
void
vopsDeparseSelectStmtForRel(StringInfo buf, PlannerInfo *root, RelOptInfo *rel,
List *tlist, List *remote_conds, List *pathkeys,
List **retrieved_attrs, List **params_list)
{
deparse_expr_cxt context;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) rel->fdw_private;
List *quals;
/*
* We handle relations for foreign tables, joins between those and upper
* relations.
*/
Assert(rel->reloptkind == RELOPT_JOINREL ||
rel->reloptkind == RELOPT_BASEREL ||
rel->reloptkind == RELOPT_OTHER_MEMBER_REL ||
rel->reloptkind == RELOPT_UPPER_REL);
/* Fill portions of context common to upper, join and base relation */
context.buf = buf;
context.root = root;
context.foreignrel = rel;
context.scanrel = (rel->reloptkind == RELOPT_UPPER_REL) ?
fpinfo->upperrel : rel;
context.params_list = params_list;
/* Construct SELECT clause */
deparseSelectSql(tlist, retrieved_attrs, &context);
/*
* For upper relations, the WHERE clause is built from the remote
* conditions of the underlying scan relation; otherwise, we can use the
* supplied list of remote conditions directly.
*/
if (rel->reloptkind == RELOPT_UPPER_REL)
{
PgFdwRelationInfo *ofpinfo;
ofpinfo = (PgFdwRelationInfo *) fpinfo->upperrel->fdw_private;
quals = ofpinfo->remote_conds;
}
else
quals = remote_conds;
/* Construct FROM and WHERE clauses */
deparseFromExpr(quals, &context);
if (rel->reloptkind == RELOPT_UPPER_REL)
{
/* Append GROUP BY clause */
appendGroupByClause(tlist, &context);
/* Append HAVING clause */
if (remote_conds)
{
appendStringInfo(buf, " HAVING ");
appendConditions(remote_conds, &context);
}
}
Assert(!pathkeys);
/* Add any necessary FOR UPDATE/SHARE. */
deparseLockingClause(&context);
}
/*
* Construct a simple SELECT statement that retrieves desired columns
* of the specified foreign table, and append it to "buf". The output
* contains just "SELECT ... ".
*
* We also create an integer List of the columns being retrieved, which is
* returned to *retrieved_attrs.
*
* tlist is the list of desired columns. Read prologue of
* deparseSelectStmtForRel() for details.
*/
static void
deparseSelectSql(List *tlist, List **retrieved_attrs, deparse_expr_cxt *context)
{
StringInfo buf = context->buf;
RelOptInfo *foreignrel = context->foreignrel;
PlannerInfo *root = context->root;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) foreignrel->fdw_private;
/*
* Construct SELECT list
*/
appendStringInfoString(buf, "SELECT ");
if (foreignrel->reloptkind == RELOPT_JOINREL ||
foreignrel->reloptkind == RELOPT_UPPER_REL)
{
/* For a join relation use the input tlist */
deparseExplicitTargetList(tlist, retrieved_attrs, context);
}
else
{
/*
* For a base relation fpinfo->attrs_used gives the list of columns
* required to be fetched from the foreign server.
*/
RangeTblEntry *rte = planner_rt_fetch(foreignrel->relid, root);
/*
* Core code already has some lock on each rel being planned, so we
* can use NoLock here.
*/
Relation rel = heap_open(rte->relid, NoLock);
deparseTargetList(buf, root, foreignrel->relid, rel, false,
fpinfo->attrs_used, false, retrieved_attrs);
heap_close(rel, NoLock);
}
}
/*
* Construct a FROM clause and, if needed, a WHERE clause, and append those to
* "buf".
*
* quals is the list of clauses to be included in the WHERE clause.
*/
static void
deparseFromExpr(List *quals, deparse_expr_cxt *context)
{
StringInfo buf = context->buf;
RelOptInfo *scanrel = context->scanrel;
/* For upper relations, scanrel must be either a joinrel or a baserel */
Assert(context->foreignrel->reloptkind != RELOPT_UPPER_REL ||
scanrel->reloptkind == RELOPT_JOINREL ||
scanrel->reloptkind == RELOPT_BASEREL);
/* Construct FROM clause */
appendStringInfoString(buf, " FROM ");
deparseFromExprForRel(buf, context->root, scanrel,
(bms_num_members(scanrel->relids) > 1),
context->params_list);
/* Construct WHERE clause */
if (quals != NIL)
{
appendStringInfo(buf, " WHERE ");
appendConditions(quals, context);
}
}
/*
* Emit a target list that retrieves the columns specified in attrs_used.
* This is used for both SELECT and RETURNING targetlists; the is_returning
* parameter is true only for a RETURNING targetlist.
*
* The tlist text is appended to buf, and we also create an integer List
* of the columns being retrieved, which is returned to *retrieved_attrs.
*
* If qualify_col is true, add relation alias before the column name.
*/
static void
deparseTargetList(StringInfo buf,
PlannerInfo *root,
Index rtindex,
Relation rel,
bool is_returning,
Bitmapset *attrs_used,
bool qualify_col,
List **retrieved_attrs)
{
TupleDesc tupdesc = RelationGetDescr(rel);
bool have_wholerow;
bool first;
int i;
*retrieved_attrs = NIL;
/* If there's a whole-row reference, we'll need all the columns. */
have_wholerow = bms_is_member(0 - FirstLowInvalidHeapAttributeNumber,
attrs_used);
first = true;
for (i = 1; i <= tupdesc->natts; i++)
{
Form_pg_attribute attr = TupleDescAttr(tupdesc, i - 1);
/* Ignore dropped attributes. */
if (attr->attisdropped)
continue;
if (have_wholerow ||
bms_is_member(i - FirstLowInvalidHeapAttributeNumber,
attrs_used))
{
if (!first)
appendStringInfoString(buf, ", ");
else if (is_returning)
appendStringInfoString(buf, " RETURNING ");
first = false;
deparseColumnRef(buf, rtindex, i, root, qualify_col);
*retrieved_attrs = lappend_int(*retrieved_attrs, i);
}
}
/*
* Add ctid and oid if needed. We currently don't support retrieving any
* other system columns.
*/
if (bms_is_member(SelfItemPointerAttributeNumber - FirstLowInvalidHeapAttributeNumber,
attrs_used))
{
if (!first)
appendStringInfoString(buf, ", ");
else if (is_returning)
appendStringInfoString(buf, " RETURNING ");
first = false;
if (qualify_col)
ADD_REL_QUALIFIER(buf, rtindex);
appendStringInfoString(buf, "ctid");
*retrieved_attrs = lappend_int(*retrieved_attrs,
SelfItemPointerAttributeNumber);
}
#if PG_VERSION_NUM<120000
if (bms_is_member(ObjectIdAttributeNumber - FirstLowInvalidHeapAttributeNumber,
attrs_used))
{
if (!first)
appendStringInfoString(buf, ", ");
else if (is_returning)
appendStringInfoString(buf, " RETURNING ");
first = false;
if (qualify_col)
ADD_REL_QUALIFIER(buf, rtindex);
appendStringInfoString(buf, "oid");
*retrieved_attrs = lappend_int(*retrieved_attrs,
ObjectIdAttributeNumber);
}
#endif
/* Don't generate bad syntax if no undropped columns */
if (first && !is_returning)
appendStringInfoString(buf, "NULL");
}
/*
* Deparse the appropriate locking clause (FOR UPDATE or FOR SHARE) for a
* given relation (context->scanrel).
*/
static void
deparseLockingClause(deparse_expr_cxt *context)
{
StringInfo buf = context->buf;
PlannerInfo *root = context->root;
RelOptInfo *rel = context->scanrel;
int relid = -1;
while ((relid = bms_next_member(rel->relids, relid)) >= 0)
{
/*
* Add FOR UPDATE/SHARE if appropriate. We apply locking during the
* initial row fetch, rather than later on as is done for local
* tables. The extra roundtrips involved in trying to duplicate the
* local semantics exactly don't seem worthwhile (see also comments
* for RowMarkType).
*
* Note: because we actually run the query as a cursor, this assumes
* that DECLARE CURSOR ... FOR UPDATE is supported, which it isn't
* before 8.3.
*/
if (relid == root->parse->resultRelation &&
(root->parse->commandType == CMD_UPDATE ||
root->parse->commandType == CMD_DELETE))
{
/* Relation is UPDATE/DELETE target, so use FOR UPDATE */
appendStringInfoString(buf, " FOR UPDATE");
/* Add the relation alias if we are here for a join relation */
if (rel->reloptkind == RELOPT_JOINREL)
appendStringInfo(buf, " OF %s%d", REL_ALIAS_PREFIX, relid);
}
else
{
PlanRowMark *rc = get_plan_rowmark(root->rowMarks, relid);
if (rc)
{
/*
* Relation is specified as a FOR UPDATE/SHARE target, so
* handle that. (But we could also see LCS_NONE, meaning this
* isn't a target relation after all.)
*
* For now, just ignore any [NO] KEY specification, since (a)
* it's not clear what that means for a remote table that we
* don't have complete information about, and (b) it wouldn't
* work anyway on older remote servers. Likewise, we don't
* worry about NOWAIT.
*/
switch (rc->strength)
{
case LCS_NONE:
/* No locking needed */
break;
case LCS_FORKEYSHARE:
case LCS_FORSHARE:
appendStringInfoString(buf, " FOR SHARE");
break;
case LCS_FORNOKEYUPDATE:
case LCS_FORUPDATE:
appendStringInfoString(buf, " FOR UPDATE");
break;
}
/* Add the relation alias if we are here for a join relation */
if (bms_num_members(rel->relids) > 1 &&
rc->strength != LCS_NONE)
appendStringInfo(buf, " OF %s%d", REL_ALIAS_PREFIX, relid);
}
}
}
}
/*
* Deparse conditions from the provided list and append them to buf.
*
* The conditions in the list are assumed to be ANDed. This function is used to
* deparse WHERE clauses, JOIN .. ON clauses and HAVING clauses.
*/
static void
appendConditions(List *exprs, deparse_expr_cxt *context)
{
ListCell *lc;
bool is_first = true;
StringInfo buf = context->buf;
foreach(lc, exprs)
{
Expr *expr = (Expr *) lfirst(lc);
/*
* Extract clause from RestrictInfo, if required. See comments in
* declaration of PgFdwRelationInfo for details.
*/
if (IsA(expr, RestrictInfo))
{
RestrictInfo *ri = (RestrictInfo *) expr;
expr = ri->clause;
}
/* Connect expressions with "AND" and parenthesize each condition. */
if (!is_first)
appendStringInfoString(buf, " AND ");
appendStringInfoChar(buf, '(');
deparseExpr(expr, context);
appendStringInfoChar(buf, ')');
is_first = false;
}
}
/*
* Deparse given targetlist and append it to context->buf.
*
* tlist is list of TargetEntry's which in turn contain Var nodes.
*
* retrieved_attrs is the list of continuously increasing integers starting
* from 1. It has same number of entries as tlist.
*/
static void
deparseExplicitTargetList(List *tlist, List **retrieved_attrs,
deparse_expr_cxt *context)
{
ListCell *lc;
StringInfo buf = context->buf;
int i = 0;
*retrieved_attrs = NIL;
foreach(lc, tlist)
{
TargetEntry *tle = castNode(TargetEntry, lfirst(lc));
if (i > 0)
appendStringInfoString(buf, ", ");
deparseExpr((Expr *) tle->expr, context);
*retrieved_attrs = lappend_int(*retrieved_attrs, i + 1);
i++;
}
if (i == 0)
appendStringInfoString(buf, "NULL");
}
/*
* Construct FROM clause for given relation
*
* The function constructs ... JOIN ... ON ... for join relation. For a base
* relation it just returns schema-qualified tablename, with the appropriate
* alias if so requested.
*/
static void
deparseFromExprForRel(StringInfo buf, PlannerInfo *root, RelOptInfo *foreignrel,
bool use_alias, List **params_list)
{
RangeTblEntry *rte = planner_rt_fetch(foreignrel->relid, root);
/*
* Core code already has some lock on each rel being planned, so we
* can use NoLock here.
*/
Relation rel = heap_open(rte->relid, NoLock);
Assert(foreignrel->reloptkind != RELOPT_JOINREL);
vopsDeparseRelation(buf, rel);
/*
* Add a unique alias to avoid any conflict in relation names due to
* pulled up subqueries in the query being built for a pushed down
* join.
*/
if (use_alias)
appendStringInfo(buf, " %s%d", REL_ALIAS_PREFIX, foreignrel->relid);
heap_close(rel, NoLock);
}
/*
* Construct name to use for given column, and emit it into buf.
* If it has a column_name FDW option, use that instead of attribute name.
*
* If qualify_col is true, qualify column name with the alias of relation.
*/
static void
deparseColumnRef(StringInfo buf, int varno, int varattno, PlannerInfo *root,
bool qualify_col)
{
RangeTblEntry *rte;
/* We support fetching the remote side's CTID and OID. */
if (varattno == SelfItemPointerAttributeNumber)
{
if (qualify_col)
ADD_REL_QUALIFIER(buf, varno);
appendStringInfoString(buf, "ctid");
}
#if PG_VERSION_NUM<120000
else if (varattno == ObjectIdAttributeNumber)
{
if (qualify_col)
ADD_REL_QUALIFIER(buf, varno);
appendStringInfoString(buf, "oid");
}
#endif
else if (varattno < 0)
{
/*
* All other system attributes are fetched as 0, except for table OID,
* which is fetched as the local table OID. However, we must be
* careful; the table could be beneath an outer join, in which case it
* must go to NULL whenever the rest of the row does.
*/
Oid fetchval = 0;
if (varattno == TableOidAttributeNumber)
{
rte = planner_rt_fetch(varno, root);
fetchval = rte->relid;
}
if (qualify_col)
{
appendStringInfoString(buf, "CASE WHEN (");
ADD_REL_QUALIFIER(buf, varno);
appendStringInfo(buf, "*)::text IS NOT NULL THEN %u END", fetchval);
}
else
appendStringInfo(buf, "%u", fetchval);
}
else if (varattno == 0)
{
/* Whole row reference */
Relation rel;
Bitmapset *attrs_used;
/* Required only to be passed down to deparseTargetList(). */
List *retrieved_attrs;
/* Get RangeTblEntry from array in PlannerInfo. */
rte = planner_rt_fetch(varno, root);
/*
* The lock on the relation will be held by upper callers, so it's
* fine to open it with no lock here.
*/
rel = heap_open(rte->relid, NoLock);
/*
* The local name of the foreign table can not be recognized by the
* foreign server and the table it references on foreign server might
* have different column ordering or different columns than those
* declared locally. Hence we have to deparse whole-row reference as
* ROW(columns referenced locally). Construct this by deparsing a
* "whole row" attribute.
*/
attrs_used = bms_add_member(NULL,
0 - FirstLowInvalidHeapAttributeNumber);
/*
* In case the whole-row reference is under an outer join then it has
* to go NULL whenever the rest of the row goes NULL. Deparsing a join
* query would always involve multiple relations, thus qualify_col
* would be true.
*/
if (qualify_col)
{