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deparse.c
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deparse.c
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/*-------------------------------------------------------------------------
*
* InfluxDB Foreign Data Wrapper for PostgreSQL
*
* Portions Copyright (c) 2018, TOSHIBA CORPORATION
*
* IDENTIFICATION
* deparse.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "influxdb_fdw.h"
#include "pgtime.h"
#include "access/heapam.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "catalog/pg_aggregate.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 "nodes/plannodes.h"
#include "optimizer/clauses.h"
#include "optimizer/tlist.h"
#include "parser/parsetree.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
#include "utils/timestamp.h"
#include "utils/typcache.h"
#define QUOTE '"'
static char *influxdb_quote_identifier(const char *s, char q);
/*
* 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;
/*
* 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;
/*
* 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;
/*
* 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,
foreign_loc_cxt *outer_cxt);
/*
* Functions to construct string representation of a node tree.
*/
static void deparseExpr(Expr *expr, deparse_expr_cxt *context);
static bool influxdb_deparse_var(Var *node, deparse_expr_cxt *context);
static void influxdb_deparse_const(Const *node, deparse_expr_cxt *context, int showtype);
static void influxdb_deparse_param(Param *node, deparse_expr_cxt *context);
static void influxdb_deparse_func_expr(FuncExpr *node, deparse_expr_cxt *context);
static void influxdb_deparse_op_expr(OpExpr *node, deparse_expr_cxt *context);
static void influxdb_deparse_operator_name(StringInfo buf, Form_pg_operator opform);
static void influxdb_deparse_scalar_array_op_expr(ScalarArrayOpExpr *node,
deparse_expr_cxt *context);
static void influxdb_deparse_relabel_type(RelabelType *node, deparse_expr_cxt *context);
static void influxdb_deparse_bool_expr(BoolExpr *node, deparse_expr_cxt *context);
static void influxdb_deparse_null_test(NullTest *node, deparse_expr_cxt *context);
static void influxdb_deparse_array_expr(ArrayExpr *node, deparse_expr_cxt *context);
static void influxdb_print_remote_param(int paramindex, Oid paramtype, int32 paramtypmod,
deparse_expr_cxt *context);
static void influxdb_print_remote_placeholder(Oid paramtype, int32 paramtypmod,
deparse_expr_cxt *context);
static void influxdb_deparse_relation(StringInfo buf, Relation rel);
static void influxdb_deparse_target_list(StringInfo buf, PlannerInfo *root, Index rtindex, Relation rel,
Bitmapset *attrs_used, List **retrieved_attrs);
static void influxdb_deparse_column_ref(StringInfo buf, int varno, int varattno, Oid vartype, PlannerInfo *root, bool convert);
static char *influxdb_get_column_ref(StringInfo buf, int varno, int varattno, Oid vartype,
PlannerInfo *root);
static void influxdb_deparse_select(List *tlist, List **retrieved_attrs, deparse_expr_cxt *context);
static void deparseFromExprForRel(StringInfo buf, PlannerInfo *root,
RelOptInfo *foreignrel,
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 appendConditions(List *exprs, deparse_expr_cxt *context);
static void appendGroupByClause(List *tlist, deparse_expr_cxt *context);
static void appendOrderByClause(List *pathkeys, deparse_expr_cxt *context);
static Node *deparseSortGroupClause(Index ref, List *tlist,
deparse_expr_cxt *context);
static void deparseExplicitTargetList(List *tlist, List **retrieved_attrs,
deparse_expr_cxt *context);
static Expr *find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel);
static bool is_builtin(Oid objectId);
/*
* Local variables.
*/
static char *cur_opname = NULL;
/*
* 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
influxdb_deparse_relation(StringInfo buf, Relation rel)
{
ForeignTable *table;
const char *relname = NULL;
ListCell *lc = NULL;
/* obtain additional catalog information. */
table = GetForeignTable(RelationGetRelid(rel));
/*
* 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, "table") == 0)
relname = defGetString(def);
}
if (relname == NULL)
relname = RelationGetRelationName(rel);
appendStringInfo(buf, "%s", influxdb_quote_identifier(relname, QUOTE));
}
static char *
influxdb_quote_identifier(const char *s, char q)
{
char *result = palloc(strlen(s) * 2 + 3);
char *r = result;
*r++ = q;
while (*s)
{
if (*s == q)
*r++ = *s;
*r++ = *s;
s++;
}
*r++ = q;
*r++ = '\0';
return result;
}
/*
* Returns true if given expr is safe to evaluate on the foreign server.
*/
bool
influxdb_is_foreign_expr(PlannerInfo *root,
RelOptInfo *baserel,
Expr *expr)
{
foreign_glob_cxt glob_cxt;
foreign_loc_cxt loc_cxt;
InfluxDBFdwRelationInfo *fpinfo = (InfluxDBFdwRelationInfo *) (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->outerrel->relids;
else
glob_cxt.relids = baserel->relids;
loc_cxt.collation = InvalidOid;
loc_cxt.state = FDW_COLLATE_NONE;
if (!foreign_expr_walker((Node *) expr, &glob_cxt, &loc_cxt))
return false;
/*
* If the expression has a valid collation that does not arise from a
* foreign var, the expression can not be sent over.
*/
if (loc_cxt.state == FDW_COLLATE_UNSAFE)
return false;
/* OK to evaluate on the remote server */
return true;
}
static bool
is_valid_type(Oid type)
{
switch (type)
{
case INT2OID:
case INT4OID:
case INT8OID:
case OIDOID:
case FLOAT4OID:
case FLOAT8OID:
case NUMERICOID:
case VARCHAROID:
case TEXTOID:
case TIMEOID:
case TIMESTAMPOID:
case TIMESTAMPTZOID:
return true;
}
return false;
}
/*
* Check if expression is safe to execute remotely, and return true if so.
*
* In addition, *outer_cxt is updated with collation information.
*
* 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;
HeapTuple tuple;
Form_pg_operator form;
char *cur_opname;
/* 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;
/*
* If the Var is from the foreign table, we consider its
* collation (if any) safe to use. If it is from another
* table, we treat its collation the same way as we would a
* Param's collation, ie it's not safe for it to have a
* non-default collation.
*/
if (bms_is_member(var->varno, glob_cxt->relids) &&
var->varlevelsup == 0)
{
/* Var belongs to foreign table */
if (var->varattno < 0)
return false;
/* Else check the collation */
collation = var->varcollid;
state = OidIsValid(collation) ? FDW_COLLATE_SAFE : FDW_COLLATE_NONE;
}
else
{
/* Var belongs to some other table */
collation = var->varcollid;
if (collation == InvalidOid ||
collation == DEFAULT_COLLATION_OID)
{
/*
* It's noncollatable, or it's safe to combine with a
* collatable foreign Var, so set state to NONE.
*/
state = FDW_COLLATE_NONE;
}
else
{
/*
* Do not fail right away, since the Var might appear
* in a collation-insensitive context.
*/
state = FDW_COLLATE_UNSAFE;
}
}
}
break;
case T_Const:
{
Const *c = (Const *) node;
if (c->consttype == INTERVALOID)
{
Interval *interval = DatumGetIntervalP(c->constvalue);
struct pg_tm tm;
fsec_t fsec;
interval2tm(*interval, &tm, &fsec);
/*
* Not pushdown interval with month or year because
* InfluxDB does not support month and year duration
*/
if (tm.tm_mon != 0 || tm.tm_year != 0)
{
return false;
}
}
/*
* 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;
if (!is_valid_type(p->paramtype))
return false;
/*
* Collation rule is same as for Consts and non-foreign Vars.
*/
collation = p->paramcollid;
if (collation == InvalidOid ||
collation == DEFAULT_COLLATION_OID)
state = FDW_COLLATE_NONE;
else
state = FDW_COLLATE_UNSAFE;
}
break;
case T_FuncExpr:
{
FuncExpr *fe = (FuncExpr *) node;
char *opername = NULL;
/* get function name and schema */
tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(fe->funcid));
if (!HeapTupleIsValid(tuple))
{
elog(ERROR, "cache lookup failed for function %u", fe->funcid);
}
opername = pstrdup(((Form_pg_proc) GETSTRUCT(tuple))->proname.data);
ReleaseSysCache(tuple);
/* pushed down to InfluxDB */
if (strcmp(opername, "now") != 0 &&
strcmp(opername, "influx_time") != 0)
{
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 if (collation == DEFAULT_COLLATION_OID)
state = FDW_COLLATE_NONE;
else
state = FDW_COLLATE_UNSAFE;
}
break;
case T_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;
tuple = SearchSysCache1(OPEROID, ObjectIdGetDatum(oe->opno));
if (!HeapTupleIsValid(tuple))
elog(ERROR, "cache lookup failed for operator %u", oe->opno);
form = (Form_pg_operator) GETSTRUCT(tuple);
/* opname is not a SQL identifier, so we should not quote it. */
cur_opname = NameStr(form->oprname);
/* ILIKE cannot be pushed down to InfluxDB */
if (strcmp(cur_opname, "~~*") == 0 || strcmp(cur_opname, "!~~*") == 0)
{
ReleaseSysCache(tuple);
return false;
}
/*
* Cannot pushdown to InfluxDB if there is string comparison with:
* "<, >, <=, >=" operators
*/
if (strcmp(cur_opname, "<") == 0
|| strcmp(cur_opname, ">") == 0
|| strcmp(cur_opname, "<=") == 0
|| strcmp(cur_opname, ">=") == 0)
{
Expr *expr;
ListCell *lc;
Const *c;
/*
* Check String type for the operand which is Const
* We do not specific any target OID for string type of constant.
* The implementation is based on implementation of influxdb_deparse_const()
* where default phrase deparses string value of constant.
*/
foreach(lc, oe->args)
{
expr = lfirst(lc);
if (!IsA(expr, Const))
continue;
c = (Const *)expr;
switch (c->consttype)
{
case INT2OID:
case INT4OID:
case INT8OID:
case OIDOID:
case FLOAT4OID:
case FLOAT8OID:
case NUMERICOID:
case BITOID:
case VARBITOID:
case BOOLOID:
case BYTEAOID:
case TIMESTAMPTZOID:
case INTERVALOID:
break;
default:
{
/* A Const expression has string type here */
ReleaseSysCache(tuple);
return false;
}
}
break;
}
}
ReleaseSysCache(tuple);
/*
* 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;
if (b->boolop == NOT_EXPR)
{
/* InfluxDB do not support not operator */
return false;
}
/*
* 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_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;
case T_Aggref:
{
Aggref *agg = (Aggref *) node;
ListCell *lc;
FuncExpr *func = (FuncExpr *) node;
char *opername = NULL;
/* get function name and schema */
tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(agg->aggfnoid));
if (!HeapTupleIsValid(tuple))
{
elog(ERROR, "cache lookup failed for function %u", func->funcid);
}
opername = pstrdup(((Form_pg_proc) GETSTRUCT(tuple))->proname.data);
ReleaseSysCache(tuple);
/* these function can be passed to InfluxDB */
if (!(strcmp(opername, "sum") == 0
|| strcmp(opername, "max") == 0
|| strcmp(opername, "min") == 0
|| strcmp(opername, "count") == 0
|| strcmp(opername, "last") == 0))
{
return false;
}
/* 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;
/*
* 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 (!IsA(n, Var))
{
return false;
}
}
if (!foreign_expr_walker(n, glob_cxt, &inner_cxt))
return false;
}
if (agg->aggorder || agg->aggfilter)
{
return false;
}
/*
* If aggregate's input collation is not derived from a
* foreign Var, it can't be sent to remote.
*/
if (agg->inputcollid == InvalidOid)
/* OK, inputs are all noncollatable */ ;
else if (inner_cxt.state != FDW_COLLATE_SAFE ||
agg->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 = agg->aggcollid;
if (collation == InvalidOid)
state = FDW_COLLATE_NONE;
else if (inner_cxt.state == FDW_COLLATE_SAFE &&
collation == inner_cxt.collation)
state = FDW_COLLATE_SAFE;
else if (collation == DEFAULT_COLLATION_OID)
state = FDW_COLLATE_NONE;
else
state = FDW_COLLATE_UNSAFE;
}
break;
case T_ArrayExpr:
case T_DistinctExpr:
/* IS DISTINCT FROM */
case T_NullTest:
return false;
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;
}
/*
* 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 contains expressions to be evaluated on
* foreign server.
*/
List *
influxdb_build_tlist_to_deparse(RelOptInfo *foreignrel)
{
List *tlist = NIL;
InfluxDBFdwRelationInfo *fpinfo = (InfluxDBFdwRelationInfo *) foreignrel->fdw_private;
ListCell *lc;
/*
* 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));
foreach(lc, fpinfo->local_conds)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
tlist = add_to_flat_tlist(tlist,
pull_var_clause((Node *) rinfo->clause,
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
influxdbDeparseSelectStmtForRel(StringInfo buf, PlannerInfo *root, RelOptInfo *rel,
List *tlist, List *remote_conds, List *pathkeys,
bool is_subquery, List **retrieved_attrs,
List **params_list)
{
deparse_expr_cxt context;
InfluxDBFdwRelationInfo *fpinfo = (InfluxDBFdwRelationInfo *) 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->outerrel : rel;
context.params_list = params_list;
/* Construct SELECT clause */
influxdb_deparse_select(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)
{
InfluxDBFdwRelationInfo *ofpinfo;
ofpinfo = (InfluxDBFdwRelationInfo *) fpinfo->outerrel->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);
}
}
/* Add ORDER BY clause if we found any useful pathkeys */
if (pathkeys)
appendOrderByClause(pathkeys, &context);
}
/*
* Deparese SELECT statment
*/
static void
influxdb_deparse_select(List *tlist, List **retrieved_attrs, deparse_expr_cxt *context)
{
StringInfo buf = context->buf;
PlannerInfo *root = context->root;
RelOptInfo *foreignrel = context->foreignrel;
InfluxDBFdwRelationInfo *fpinfo = (InfluxDBFdwRelationInfo *) foreignrel->fdw_private;
/*
* Construct SELECT list
*/
appendStringInfoString(buf, "SELECT ");
if (foreignrel->reloptkind == RELOPT_JOINREL ||
foreignrel->reloptkind == RELOPT_UPPER_REL)
{
/*
* For a join or upper relation the input tlist gives the list of
* columns required to be fetched from the foreign server.
*/
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);
influxdb_deparse_target_list(buf, root, foreignrel->relid, rel, fpinfo->attrs_used, retrieved_attrs);
heap_close(rel, NoLock);
}
}
/*