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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.
*
* We do not consider that it is ever safe to send COLLATE expressions to
* the remote server: it might not have the same collation names we do.
* (Later we might consider it safe to send COLLATE "C", but even that would
* fail on old remote servers.) An expression is considered safe to send only
* if all collations used in it are traceable to Var(s) of the foreign table.
* That implies that if the remote server gets a different answer than we do,
* the foreign table's columns are not marked with collations that match the
* remote table's columns, which we can consider to be user error.
*
* Portions Copyright (c) 2012-2013, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/postgres_fdw/deparse.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "postgres_fdw.h"
#include "access/htup.h"
#include "access/sysattr.h"
#include "access/transam.h"
#include "catalog/pg_collation.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/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/var.h"
#include "parser/parsetree.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
/*
* Global context for foreign_expr_walker's search of an expression tree.
*/
typedef struct foreign_glob_cxt
{
/* Input values */
PlannerInfo *root;
RelOptInfo *foreignrel;
/* Result values */
List *param_numbers; /* Param IDs of PARAM_EXTERN Params */
} foreign_glob_cxt;
/*
* Local (per-tree-level) context for foreign_expr_walker's search.
* This is concerned with identifying collations used in the expression.
*/
typedef enum
{
FDW_COLLATE_NONE, /* expression is of a noncollatable type */
FDW_COLLATE_SAFE, /* collation derives from a foreign Var */
FDW_COLLATE_UNSAFE /* collation derives from something else */
} FDWCollateState;
typedef struct foreign_loc_cxt
{
Oid collation; /* OID of current collation, if any */
FDWCollateState state; /* state of current collation choice */
} foreign_loc_cxt;
/*
* Functions to determine whether an expression can be evaluated safely on
* remote server.
*/
static bool is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel,
Expr *expr, List **param_numbers);
static bool foreign_expr_walker(Node *node,
foreign_glob_cxt *glob_cxt,
foreign_loc_cxt *outer_cxt);
static bool is_builtin(Oid procid);
/*
* Functions to construct string representation of a node tree.
*/
static void deparseColumnRef(StringInfo buf, int varno, int varattno,
PlannerInfo *root);
static void deparseRelation(StringInfo buf, Oid relid);
static void deparseStringLiteral(StringInfo buf, const char *val);
static void deparseExpr(StringInfo buf, Expr *expr, PlannerInfo *root);
static void deparseVar(StringInfo buf, Var *node, PlannerInfo *root);
static void deparseConst(StringInfo buf, Const *node, PlannerInfo *root);
static void deparseParam(StringInfo buf, Param *node, PlannerInfo *root);
static void deparseArrayRef(StringInfo buf, ArrayRef *node, PlannerInfo *root);
static void deparseFuncExpr(StringInfo buf, FuncExpr *node, PlannerInfo *root);
static void deparseOpExpr(StringInfo buf, OpExpr *node, PlannerInfo *root);
static void deparseOperatorName(StringInfo buf, Form_pg_operator opform);
static void deparseDistinctExpr(StringInfo buf, DistinctExpr *node,
PlannerInfo *root);
static void deparseScalarArrayOpExpr(StringInfo buf, ScalarArrayOpExpr *node,
PlannerInfo *root);
static void deparseRelabelType(StringInfo buf, RelabelType *node,
PlannerInfo *root);
static void deparseBoolExpr(StringInfo buf, BoolExpr *node, PlannerInfo *root);
static void deparseNullTest(StringInfo buf, NullTest *node, PlannerInfo *root);
static void deparseArrayExpr(StringInfo buf, ArrayExpr *node,
PlannerInfo *root);
/*
* Examine each restriction clause in baserel's baserestrictinfo list,
* and classify them into three groups, which are returned as three lists:
* - remote_conds contains expressions that can be evaluated remotely,
* and contain no PARAM_EXTERN Params
* - param_conds contains expressions that can be evaluated remotely,
* but contain one or more PARAM_EXTERN Params
* - local_conds contains all expressions that can't be evaluated remotely
*
* In addition, the fourth output parameter param_numbers receives an integer
* list of the param IDs of the PARAM_EXTERN Params used in param_conds.
*
* The reason for segregating param_conds is mainly that it's difficult to
* use such conditions in remote EXPLAIN. We could do it, but unless the
* planner has been given representative values for all the Params, we'd
* have to guess at representative values to use in EXPLAIN EXECUTE.
* So for now we don't include them when doing remote EXPLAIN.
*/
void
classifyConditions(PlannerInfo *root,
RelOptInfo *baserel,
List **remote_conds,
List **param_conds,
List **local_conds,
List **param_numbers)
{
ListCell *lc;
*remote_conds = NIL;
*param_conds = NIL;
*local_conds = NIL;
*param_numbers = NIL;
foreach(lc, baserel->baserestrictinfo)
{
RestrictInfo *ri = (RestrictInfo *) lfirst(lc);
List *cur_param_numbers;
if (is_foreign_expr(root, baserel, ri->clause, &cur_param_numbers))
{
if (cur_param_numbers == NIL)
*remote_conds = lappend(*remote_conds, ri);
else
{
*param_conds = lappend(*param_conds, ri);
/* Use list_concat_unique_int to get rid of duplicates */
*param_numbers = list_concat_unique_int(*param_numbers,
cur_param_numbers);
}
}
else
*local_conds = lappend(*local_conds, ri);
}
}
/*
* Returns true if given expr is safe to evaluate on the foreign server.
*
* If result is true, we also return a list of param IDs of PARAM_EXTERN
* Params appearing in the expr into *param_numbers.
*/
static bool
is_foreign_expr(PlannerInfo *root,
RelOptInfo *baserel,
Expr *expr,
List **param_numbers)
{
foreign_glob_cxt glob_cxt;
foreign_loc_cxt loc_cxt;
*param_numbers = NIL; /* default result */
/*
* Check that the expression consists of nodes that are safe to execute
* remotely.
*/
glob_cxt.root = root;
glob_cxt.foreignrel = baserel;
glob_cxt.param_numbers = NIL;
loc_cxt.collation = InvalidOid;
loc_cxt.state = FDW_COLLATE_NONE;
if (!foreign_expr_walker((Node *) expr, &glob_cxt, &loc_cxt))
return false;
/* Expressions examined here should be boolean, ie noncollatable */
Assert(loc_cxt.collation == InvalidOid);
Assert(loc_cxt.state == FDW_COLLATE_NONE);
/*
* An expression which includes any mutable functions can't be sent over
* because its result is not stable. For example, sending now() remote
* side could cause confusion from clock offsets. Future versions might
* be able to make this choice with more granularity. (We check this last
* because it requires a lot of expensive catalog lookups.)
*/
if (contain_mutable_functions((Node *) expr))
return false;
/*
* OK, so return list of param IDs too.
*/
*param_numbers = glob_cxt.param_numbers;
return true;
}
/*
* Check if expression is safe to execute remotely, and return true if so.
*
* In addition, glob_cxt->param_numbers and *outer_cxt are updated.
*
* We must check that the expression contains only node types we can deparse,
* that all types/functions/operators are safe to send (which we approximate
* as being built-in), and that all collations used in the expression derive
* from Vars of the foreign table. Because of the latter, the logic is
* pretty close to assign_collations_walker() in parse_collate.c, though we
* can assume here that the given expression is valid.
*/
static bool
foreign_expr_walker(Node *node,
foreign_glob_cxt *glob_cxt,
foreign_loc_cxt *outer_cxt)
{
bool check_type = true;
foreign_loc_cxt inner_cxt;
Oid collation;
FDWCollateState state;
/* Need do nothing for empty subexpressions */
if (node == NULL)
return true;
/* Set up inner_cxt for possible recursion to child nodes */
inner_cxt.collation = InvalidOid;
inner_cxt.state = FDW_COLLATE_NONE;
switch (nodeTag(node))
{
case T_Var:
{
Var *var = (Var *) node;
/*
* Var can be used if it is in the foreign table (we shouldn't
* really see anything else in baserestrict clauses, but let's
* check anyway).
*/
if (var->varno != glob_cxt->foreignrel->relid ||
var->varlevelsup != 0)
return false;
/*
* If Var has a collation, consider that safe to use.
*/
collation = var->varcollid;
state = OidIsValid(collation) ? FDW_COLLATE_SAFE : FDW_COLLATE_NONE;
}
break;
case T_Const:
{
Const *c = (Const *) node;
/*
* If the constant has nondefault collation, either it's of a
* non-builtin type, or it reflects folding of a CollateExpr;
* either way, it's unsafe to send to the remote.
*/
if (c->constcollid != InvalidOid &&
c->constcollid != DEFAULT_COLLATION_OID)
return false;
/* Otherwise, we can consider that it doesn't set collation */
collation = InvalidOid;
state = FDW_COLLATE_NONE;
}
break;
case T_Param:
{
Param *p = (Param *) node;
/*
* Only external parameters can be sent to remote. (XXX This
* needs to be improved, but at the point where this code
* runs, we should only see PARAM_EXTERN Params anyway.)
*/
if (p->paramkind != PARAM_EXTERN)
return false;
/*
* Collation handling is same as for Consts.
*/
if (p->paramcollid != InvalidOid &&
p->paramcollid != DEFAULT_COLLATION_OID)
return false;
collation = InvalidOid;
state = FDW_COLLATE_NONE;
/*
* Report IDs of PARAM_EXTERN Params. We don't bother to
* eliminate duplicate list elements here; classifyConditions
* will do that.
*/
glob_cxt->param_numbers = lappend_int(glob_cxt->param_numbers,
p->paramid);
}
break;
case T_ArrayRef:
{
ArrayRef *ar = (ArrayRef *) node;;
/* Assignment should not be in restrictions. */
if (ar->refassgnexpr != NULL)
return false;
/*
* Recurse to remaining subexpressions. Since the array
* subscripts must yield (noncollatable) integers, they won't
* affect the inner_cxt state.
*/
if (!foreign_expr_walker((Node *) ar->refupperindexpr,
glob_cxt, &inner_cxt))
return false;
if (!foreign_expr_walker((Node *) ar->reflowerindexpr,
glob_cxt, &inner_cxt))
return false;
if (!foreign_expr_walker((Node *) ar->refexpr,
glob_cxt, &inner_cxt))
return false;
/*
* Array subscripting should yield same collation as input,
* but for safety use same logic as for function nodes.
*/
collation = ar->refcollid;
if (collation == InvalidOid)
state = FDW_COLLATE_NONE;
else if (inner_cxt.state == FDW_COLLATE_SAFE &&
collation == inner_cxt.collation)
state = FDW_COLLATE_SAFE;
else
state = FDW_COLLATE_UNSAFE;
}
break;
case T_FuncExpr:
{
FuncExpr *fe = (FuncExpr *) node;
/*
* If function used by the expression is not built-in, it
* can't be sent to remote because it might have incompatible
* semantics on remote side.
*/
if (!is_builtin(fe->funcid))
return false;
/*
* Recurse to input subexpressions.
*/
if (!foreign_expr_walker((Node *) fe->args,
glob_cxt, &inner_cxt))
return false;
/*
* If function's input collation is not derived from a foreign
* Var, it can't be sent to remote.
*/
if (fe->inputcollid == InvalidOid)
/* OK, inputs are all noncollatable */ ;
else if (inner_cxt.state != FDW_COLLATE_SAFE ||
fe->inputcollid != inner_cxt.collation)
return false;
/*
* Detect whether node is introducing a collation not derived
* from a foreign Var. (If so, we just mark it unsafe for now
* rather than immediately returning false, since the parent
* node might not care.)
*/
collation = fe->funccollid;
if (collation == InvalidOid)
state = FDW_COLLATE_NONE;
else if (inner_cxt.state == FDW_COLLATE_SAFE &&
collation == inner_cxt.collation)
state = FDW_COLLATE_SAFE;
else
state = FDW_COLLATE_UNSAFE;
}
break;
case T_OpExpr:
case T_DistinctExpr: /* struct-equivalent to OpExpr */
{
OpExpr *oe = (OpExpr *) node;
/*
* Similarly, only built-in operators can be sent to remote.
* (If the operator is, surely its underlying function is
* too.)
*/
if (!is_builtin(oe->opno))
return false;
/*
* Recurse to input subexpressions.
*/
if (!foreign_expr_walker((Node *) oe->args,
glob_cxt, &inner_cxt))
return false;
/*
* If operator's input collation is not derived from a foreign
* Var, it can't be sent to remote.
*/
if (oe->inputcollid == InvalidOid)
/* OK, inputs are all noncollatable */ ;
else if (inner_cxt.state != FDW_COLLATE_SAFE ||
oe->inputcollid != inner_cxt.collation)
return false;
/* Result-collation handling is same as for functions */
collation = oe->opcollid;
if (collation == InvalidOid)
state = FDW_COLLATE_NONE;
else if (inner_cxt.state == FDW_COLLATE_SAFE &&
collation == inner_cxt.collation)
state = FDW_COLLATE_SAFE;
else
state = FDW_COLLATE_UNSAFE;
}
break;
case T_ScalarArrayOpExpr:
{
ScalarArrayOpExpr *oe = (ScalarArrayOpExpr *) node;
/*
* Again, only built-in operators can be sent to remote.
*/
if (!is_builtin(oe->opno))
return false;
/*
* Recurse to input subexpressions.
*/
if (!foreign_expr_walker((Node *) oe->args,
glob_cxt, &inner_cxt))
return false;
/*
* If operator's input collation is not derived from a foreign
* Var, it can't be sent to remote.
*/
if (oe->inputcollid == InvalidOid)
/* OK, inputs are all noncollatable */ ;
else if (inner_cxt.state != FDW_COLLATE_SAFE ||
oe->inputcollid != inner_cxt.collation)
return false;
/* Output is always boolean and so noncollatable. */
collation = InvalidOid;
state = FDW_COLLATE_NONE;
}
break;
case T_RelabelType:
{
RelabelType *r = (RelabelType *) node;
/*
* Recurse to input subexpression.
*/
if (!foreign_expr_walker((Node *) r->arg,
glob_cxt, &inner_cxt))
return false;
/*
* RelabelType must not introduce a collation not derived from
* an input foreign Var.
*/
collation = r->resultcollid;
if (collation == InvalidOid)
state = FDW_COLLATE_NONE;
else if (inner_cxt.state == FDW_COLLATE_SAFE &&
collation == inner_cxt.collation)
state = FDW_COLLATE_SAFE;
else
state = FDW_COLLATE_UNSAFE;
}
break;
case T_BoolExpr:
{
BoolExpr *b = (BoolExpr *) node;
/*
* Recurse to input subexpressions.
*/
if (!foreign_expr_walker((Node *) b->args,
glob_cxt, &inner_cxt))
return false;
/* Output is always boolean and so noncollatable. */
collation = InvalidOid;
state = FDW_COLLATE_NONE;
}
break;
case T_NullTest:
{
NullTest *nt = (NullTest *) node;
/*
* Recurse to input subexpressions.
*/
if (!foreign_expr_walker((Node *) nt->arg,
glob_cxt, &inner_cxt))
return false;
/* Output is always boolean and so noncollatable. */
collation = InvalidOid;
state = FDW_COLLATE_NONE;
}
break;
case T_ArrayExpr:
{
ArrayExpr *a = (ArrayExpr *) node;
/*
* Recurse to input subexpressions.
*/
if (!foreign_expr_walker((Node *) a->elements,
glob_cxt, &inner_cxt))
return false;
/*
* ArrayExpr must not introduce a collation not derived from
* an input foreign Var.
*/
collation = a->array_collid;
if (collation == InvalidOid)
state = FDW_COLLATE_NONE;
else if (inner_cxt.state == FDW_COLLATE_SAFE &&
collation == inner_cxt.collation)
state = FDW_COLLATE_SAFE;
else
state = FDW_COLLATE_UNSAFE;
}
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, &inner_cxt))
return false;
}
/*
* When processing a list, collation state just bubbles up
* from the list elements.
*/
collation = inner_cxt.collation;
state = inner_cxt.state;
/* Don't apply exprType() to the list. */
check_type = 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;
}
/*
* If result type of given expression is not built-in, it can't be sent to
* remote because it might have incompatible semantics on remote side.
*/
if (check_type && !is_builtin(exprType(node)))
return false;
/*
* Now, merge my collation information into my parent's state.
*/
if (state > outer_cxt->state)
{
/* Override previous parent state */
outer_cxt->collation = collation;
outer_cxt->state = state;
}
else if (state == outer_cxt->state)
{
/* Merge, or detect error if there's a collation conflict */
switch (state)
{
case FDW_COLLATE_NONE:
/* Nothing + nothing is still nothing */
break;
case FDW_COLLATE_SAFE:
if (collation != outer_cxt->collation)
{
/*
* Non-default collation always beats default.
*/
if (outer_cxt->collation == DEFAULT_COLLATION_OID)
{
/* Override previous parent state */
outer_cxt->collation = collation;
}
else if (collation != DEFAULT_COLLATION_OID)
{
/*
* Conflict; show state as indeterminate. We don't
* want to "return false" right away, since parent
* node might not care about collation.
*/
outer_cxt->state = FDW_COLLATE_UNSAFE;
}
}
break;
case FDW_COLLATE_UNSAFE:
/* We're still conflicted ... */
break;
}
}
/* It looks OK */
return true;
}
/*
* Return true if given object is one of PostgreSQL's built-in objects.
*
* We use FirstBootstrapObjectId as the cutoff, so that we only consider
* objects with hand-assigned OIDs to be "built in", not for instance any
* function or type defined in the information_schema.
*
* Our constraints for dealing with types are tighter than they are for
* functions or operators: we want to accept only types that are in pg_catalog,
* else format_type might incorrectly fail to schema-qualify their names.
* (This could be fixed with some changes to format_type, but for now there's
* no need.) Thus we must exclude information_schema types.
*
* XXX there is a problem with this, which is that the set of built-in
* objects expands over time. Something that is built-in to us might not
* be known to the remote server, if it's of an older version. But keeping
* track of that would be a huge exercise.
*/
static bool
is_builtin(Oid oid)
{
return (oid < FirstBootstrapObjectId);
}
/*
* Construct a simple SELECT statement that retrieves interesting columns
* of the specified foreign table, and append it to "buf". The output
* contains just "SELECT ... FROM tablename".
*
* "Interesting" columns are those appearing in the rel's targetlist or
* in local_conds (conditions which can't be executed remotely).
*/
void
deparseSimpleSql(StringInfo buf,
PlannerInfo *root,
RelOptInfo *baserel,
List *local_conds)
{
RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
Bitmapset *attrs_used = NULL;
bool have_wholerow;
bool first;
AttrNumber attr;
ListCell *lc;
/* Collect all the attributes needed for joins or final output. */
pull_varattnos((Node *) baserel->reltargetlist, baserel->relid,
&attrs_used);
/* Add all the attributes used by local_conds. */
foreach(lc, local_conds)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
pull_varattnos((Node *) rinfo->clause, baserel->relid,
&attrs_used);
}
/* If there's a whole-row reference, we'll need all the columns. */
have_wholerow = bms_is_member(0 - FirstLowInvalidHeapAttributeNumber,
attrs_used);
/*
* Construct SELECT list
*
* We list attributes in order of the foreign table's columns, but replace
* any attributes that need not be fetched with NULL constants. (We can't
* just omit such attributes, or we'll lose track of which columns are
* which at runtime.) Note however that any dropped columns are ignored.
*/
appendStringInfo(buf, "SELECT ");
first = true;
for (attr = 1; attr <= baserel->max_attr; attr++)
{
/* Ignore dropped attributes. */
if (get_rte_attribute_is_dropped(rte, attr))
continue;
if (!first)
appendStringInfo(buf, ", ");
first = false;
if (have_wholerow ||
bms_is_member(attr - FirstLowInvalidHeapAttributeNumber,
attrs_used))
deparseColumnRef(buf, baserel->relid, attr, root);
else
appendStringInfo(buf, "NULL");
}
/* Don't generate bad syntax if no undropped columns */
if (first)
appendStringInfo(buf, "NULL");
/*
* Construct FROM clause
*/
appendStringInfo(buf, " FROM ");
deparseRelation(buf, rte->relid);
}
/*
* Deparse WHERE clauses in given list of RestrictInfos and append them to buf.
*
* If no WHERE clause already exists in the buffer, is_first should be true.
*/
void
appendWhereClause(StringInfo buf,
bool is_first,
List *exprs,
PlannerInfo *root)
{
int nestlevel;
ListCell *lc;
/* Make sure any constants in the exprs are printed portably */
nestlevel = set_transmission_modes();
foreach(lc, exprs)
{
RestrictInfo *ri = (RestrictInfo *) lfirst(lc);
/* Connect expressions with "AND" and parenthesize each condition. */
if (is_first)
appendStringInfo(buf, " WHERE ");
else
appendStringInfo(buf, " AND ");
appendStringInfoChar(buf, '(');
deparseExpr(buf, ri->clause, root);
appendStringInfoChar(buf, ')');
is_first = false;
}
reset_transmission_modes(nestlevel);
}
/*
* Construct SELECT statement to acquire size in blocks of given relation.
*
* Note: we use local definition of block size, not remote definition.
* This is perhaps debatable.
*
* Note: pg_relation_size() exists in 8.1 and later.
*/
void
deparseAnalyzeSizeSql(StringInfo buf, Relation rel)
{
Oid relid = RelationGetRelid(rel);
StringInfoData relname;
/* We'll need the remote relation name as a literal. */
initStringInfo(&relname);
deparseRelation(&relname, relid);
appendStringInfo(buf, "SELECT pg_catalog.pg_relation_size(");
deparseStringLiteral(buf, relname.data);
appendStringInfo(buf, "::pg_catalog.regclass) / %d", BLCKSZ);
}
/*
* Construct SELECT statement to acquire sample rows of given relation.
*
* Note: command is appended to whatever might be in buf already.
*/
void
deparseAnalyzeSql(StringInfo buf, Relation rel)
{
Oid relid = RelationGetRelid(rel);
TupleDesc tupdesc = RelationGetDescr(rel);
int i;
char *colname;
List *options;
ListCell *lc;
bool first = true;
appendStringInfo(buf, "SELECT ");
for (i = 0; i < tupdesc->natts; i++)
{
/* Ignore dropped columns. */
if (tupdesc->attrs[i]->attisdropped)
continue;
/* Use attribute name or column_name option. */
colname = NameStr(tupdesc->attrs[i]->attname);
options = GetForeignColumnOptions(relid, i + 1);
foreach(lc, options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "column_name") == 0)
{
colname = defGetString(def);
break;
}
}
if (!first)
appendStringInfo(buf, ", ");
appendStringInfoString(buf, quote_identifier(colname));
first = false;
}
/* Don't generate bad syntax for zero-column relation. */
if (first)
appendStringInfo(buf, "NULL");
/*
* Construct FROM clause
*/
appendStringInfo(buf, " FROM ");
deparseRelation(buf, relid);
}
/*
* 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.
*/
static void
deparseColumnRef(StringInfo buf, int varno, int varattno, PlannerInfo *root)
{
RangeTblEntry *rte;
char *colname = NULL;
List *options;
ListCell *lc;
/* varno must not be any of OUTER_VAR, INNER_VAR and INDEX_VAR. */
Assert(varno >= 1 && varno <= root->simple_rel_array_size);
/* Get RangeTblEntry from array in PlannerInfo. */
rte = root->simple_rte_array[varno];
/*
* If it's a column of a foreign table, and it has the column_name FDW
* option, use that value.
*/
options = GetForeignColumnOptions(rte->relid, varattno);
foreach(lc, options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "column_name") == 0)
{
colname = defGetString(def);
break;
}
}
/*
* If it's a column of a regular table or it doesn't have column_name FDW
* option, use attribute name.
*/
if (colname == NULL)
colname = get_relid_attribute_name(rte->relid, varattno);
appendStringInfoString(buf, quote_identifier(colname));
}
/*
* Append remote name of specified foreign table to buf.
* Use value of table_name FDW option (if any) instead of relation's name.
* Similarly, schema_name FDW option overrides schema name.
*/
static void
deparseRelation(StringInfo buf, Oid relid)
{
ForeignTable *table;
const char *nspname = NULL;
const char *relname = NULL;
ListCell *lc;
/* obtain additional catalog information. */
table = GetForeignTable(relid);
/*
* Use value of FDW options if any, instead of the name of object itself.
*/
foreach(lc, table->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "schema_name") == 0)
nspname = defGetString(def);
else if (strcmp(def->defname, "table_name") == 0)
relname = defGetString(def);
}
/*
* Note: we could skip printing the schema name if it's pg_catalog,
* but that doesn't seem worth the trouble.
*/
if (nspname == NULL)
nspname = get_namespace_name(get_rel_namespace(relid));
if (relname == NULL)
relname = get_rel_name(relid);
appendStringInfo(buf, "%s.%s",
quote_identifier(nspname), quote_identifier(relname));
}
/*
* Append a SQL string literal representing "val" to buf.
*/
static void
deparseStringLiteral(StringInfo buf, const char *val)
{
const char *valptr;
/*
* Rather than making assumptions about the remote server's value of
* standard_conforming_strings, always use E'foo' syntax if there are any
* backslashes. This will fail on remote servers before 8.1, but those
* are long out of support.
*/
if (strchr(val, '\\') != NULL)
appendStringInfoChar(buf, ESCAPE_STRING_SYNTAX);
appendStringInfoChar(buf, '\'');
for (valptr = val; *valptr; valptr++)
{
char ch = *valptr;
if (SQL_STR_DOUBLE(ch, true))
appendStringInfoChar(buf, ch);
appendStringInfoChar(buf, ch);
}
appendStringInfoChar(buf, '\'');
}
/*
* Deparse given expression into buf.
*
* This function must support all the same node types that foreign_expr_walker
* accepts.
*
* Note: unlike ruleutils.c, we just use a simple hard-wired parenthesization
* scheme: anything more complex than a Var, Const, function call or cast
* should be self-parenthesized.
*/
static void
deparseExpr(StringInfo buf, Expr *node, PlannerInfo *root)
{
if (node == NULL)