void
CreateModel(CreateModelStmt *stmt,const char *queryString, DestReceiver *dest, char *completionTag)
{
List *query_list;
List *planned_list;
const char *commandTag;
Portal portal;
DestReceiver *tupledest;
// create command Tag
commandTag = CreateCommandTag(stmt->algorithmclause->trainingdata);
// Rewrite the already analyzed Select query for the training data
query_list = pg_rewrite_query((Query *)stmt->algorithmclause->trainingdata);
// plan the query
planned_list = pg_plan_queries(query_list,0,NULL);
// results should be send to the ModelReceiver
tupledest = CreateModelDestReceiver(stmt->modelname,
(TargetEntry *)stmt->outputcolumn,
stmt->timecolumns,
((Query *)stmt->algorithmclause->trainingdata)->jointree->quals,
queryString,stmt->algorithmclause->algorithmname,
((AlgorithmClause *)copyObject(stmt->algorithmclause))->algorithmparameter,
0);
// Create a new portal to run the query in
portal = CreateNewPortal();
//Don't display the portal in pg_cursors, it is for internal use only
portal->visible = false;
PortalDefineQuery(portal,
NULL,
queryString,
commandTag,
planned_list,
NULL);
// Start the portal. No parameters here.
PortalStart(portal, NULL, InvalidSnapshot);
(void) PortalRun(portal, FETCH_ALL, false, tupledest, tupledest, completionTag);
// Drop portal and receiver
(*tupledest->rDestroy) (tupledest);
PortalDrop(portal, false);
}
/*
* Implements the 'EXECUTE' utility statement.
*/
void
ExecuteQuery(ExecuteStmt *stmt, ParamListInfo params,
DestReceiver *dest, char *completionTag)
{
PreparedStatement *entry;
char *query_string;
List *query_list,
*plan_list;
MemoryContext qcontext;
ParamListInfo paramLI = NULL;
EState *estate = NULL;
Portal portal;
/* Look it up in the hash table */
entry = FetchPreparedStatement(stmt->name, true);
query_string = entry->query_string;
query_list = entry->query_list;
plan_list = entry->plan_list;
qcontext = entry->context;
Assert(list_length(query_list) == list_length(plan_list));
/* Evaluate parameters, if any */
if (entry->argtype_list != NIL)
{
/*
* Need an EState to evaluate parameters; must not delete it till end
* of query, in case parameters are pass-by-reference.
*/
estate = CreateExecutorState();
estate->es_param_list_info = params;
paramLI = EvaluateParams(estate, stmt->params, entry->argtype_list);
}
/* Create a new portal to run the query in */
portal = CreateNewPortal();
/* Don't display the portal in pg_cursors, it is for internal use only */
portal->visible = false;
/*
* For CREATE TABLE / AS EXECUTE, make a copy of the stored query so that
* we can modify its destination (yech, but this has always been ugly).
* For regular EXECUTE we can just use the stored query where it sits,
* since the executor is read-only.
*/
if (stmt->into)
{
MemoryContext oldContext;
Query *query;
oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
if (query_string)
query_string = pstrdup(query_string);
query_list = copyObject(query_list);
plan_list = copyObject(plan_list);
qcontext = PortalGetHeapMemory(portal);
if (list_length(query_list) != 1)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("prepared statement is not a SELECT")));
query = (Query *) linitial(query_list);
if (query->commandType != CMD_SELECT)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("prepared statement is not a SELECT")));
query->into = copyObject(stmt->into);
query->intoOptions = copyObject(stmt->intoOptions);
query->intoOnCommit = stmt->into_on_commit;
if (stmt->into_tbl_space)
query->intoTableSpaceName = pstrdup(stmt->into_tbl_space);
MemoryContextSwitchTo(oldContext);
}
PortalDefineQuery(portal,
NULL,
query_string,
entry->commandTag,
query_list,
plan_list,
qcontext);
/*
* Run the portal to completion.
*/
PortalStart(portal, paramLI, ActiveSnapshot);
(void) PortalRun(portal, FETCH_ALL, dest, dest, completionTag);
PortalDrop(portal, false);
if (estate)
FreeExecutorState(estate);
/* No need to pfree other memory, MemoryContext will be reset */
}
/*
* Implements the 'EXECUTE' utility statement.
*
* Note: this is one of very few places in the code that needs to deal with
* two query strings at once. The passed-in queryString is that of the
* EXECUTE, which we might need for error reporting while processing the
* parameter expressions. The query_string that we copy from the plan
* source is that of the original PREPARE.
*/
void
ExecuteQuery(ExecuteStmt *stmt, const char *queryString,
ParamListInfo params,
DestReceiver *dest, char *completionTag)
{
PreparedStatement *entry;
List *stmt_list;
MemoryContext qcontext;
ParamListInfo paramLI = NULL;
EState *estate = NULL;
Portal portal;
/* Look it up in the hash table */
entry = FetchPreparedStatement(stmt->name, true);
qcontext = entry->context;
/* Evaluate parameters, if any */
if (entry->argtype_list != NIL)
{
/*
* Need an EState to evaluate parameters; must not delete it till end
* of query, in case parameters are pass-by-reference.
*/
estate = CreateExecutorState();
estate->es_param_list_info = params;
paramLI = EvaluateParams(estate, stmt->params, entry->argtype_list);
}
/* Create a new portal to run the query in */
portal = CreateNewPortal();
/* Don't display the portal in pg_cursors, it is for internal use only */
portal->visible = false;
/* Plan the query. If this is a CTAS, copy the "into" information into
* the query so that we construct the plan correctly. Else the table
* might not be created on the segments. (MPP-8135) */
{
List *query_list = copyObject(entry->query_list); /* planner scribbles on query tree :( */
if ( stmt->into )
{
Query *query = (Query*)linitial(query_list);
Assert(IsA(query, Query) && query->intoClause == NULL);
query->intoClause = copyObject(stmt->into);
}
stmt_list = pg_plan_queries(query_list, paramLI, false, QRL_ONCE);
}
/*
* For CREATE TABLE / AS EXECUTE, make a copy of the stored query so that
* we can modify its destination (yech, but this has always been ugly).
* For regular EXECUTE we can just use the stored query where it sits,
* since the executor is read-only.
*/
if (stmt->into)
{
MemoryContext oldContext;
PlannedStmt *pstmt;
if (list_length(stmt_list) != 1)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("prepared statement is not a SELECT")));
oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
stmt_list = copyObject(stmt_list);
qcontext = PortalGetHeapMemory(portal);
pstmt = (PlannedStmt *) linitial(stmt_list);
pstmt->qdContext = qcontext;
if (pstmt->commandType != CMD_SELECT)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("prepared statement is not a SELECT"),
errOmitLocation(true)));
pstmt->intoClause = copyObject(stmt->into);
/* XXX Is it legitimate to assign a constant default policy without
* even checking the relation?
*/
pstmt->intoPolicy = palloc0(sizeof(GpPolicy)- sizeof(pstmt->intoPolicy->attrs)
+ 255 * sizeof(pstmt->intoPolicy->attrs[0]));
pstmt->intoPolicy->nattrs = 0;
pstmt->intoPolicy->ptype = POLICYTYPE_PARTITIONED;
pstmt->intoPolicy->bucketnum = GetRelOpt_bucket_num_fromRangeVar(stmt->into->rel, GetRandomDistPartitionNum());
MemoryContextSwitchTo(oldContext);
}
/* Copy the plan's saved query string into the portal's memory */
Assert(entry->query_string != NULL);
char *query_string = MemoryContextStrdup(PortalGetHeapMemory(portal),
entry->query_string);
PortalDefineQuery(portal,
NULL,
query_string,
entry->sourceTag,
entry->commandTag,
stmt_list,
qcontext);
create_filesystem_credentials(portal);
/*
* Run the portal to completion.
*/
PortalStart(portal, paramLI, ActiveSnapshot,
savedSeqServerHost, savedSeqServerPort);
(void) PortalRun(portal,
FETCH_ALL,
true, /* Effectively always top level. */
dest,
dest,
completionTag);
PortalDrop(portal, false);
if (estate)
FreeExecutorState(estate);
/* No need to pfree other memory, MemoryContext will be reset */
}
/*
* PerformCursorOpen
* Execute SQL DECLARE CURSOR command.
*
* The query has already been through parse analysis, rewriting, and planning.
* When it gets here, it looks like a SELECT PlannedStmt, except that the
* utilityStmt field is set.
*/
void
PerformCursorOpen(PlannedStmt *stmt, ParamListInfo params,
const char *queryString, bool isTopLevel)
{
DeclareCursorStmt *cstmt = (DeclareCursorStmt *) stmt->utilityStmt;
Portal portal;
MemoryContext oldContext;
if (cstmt == NULL || !IsA(cstmt, DeclareCursorStmt))
elog(ERROR, "PerformCursorOpen called for non-cursor query");
/*
* Disallow empty-string cursor name (conflicts with protocol-level
* unnamed portal).
*/
if (!cstmt->portalname || cstmt->portalname[0] == '\0')
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_NAME),
errmsg("invalid cursor name: must not be empty")));
/*
* If this is a non-holdable cursor, we require that this statement has
* been executed inside a transaction block (or else, it would have no
* user-visible effect).
*/
if (!(cstmt->options & CURSOR_OPT_HOLD))
RequireTransactionChain(isTopLevel, "DECLARE CURSOR");
/*
* Create a portal and copy the plan and queryString into its memory.
*/
portal = CreatePortal(cstmt->portalname, false, false);
oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
stmt = copyObject(stmt);
stmt->utilityStmt = NULL; /* make it look like plain SELECT */
queryString = pstrdup(queryString);
PortalDefineQuery(portal,
NULL,
queryString,
"SELECT", /* cursor's query is always a SELECT */
list_make1(stmt),
NULL);
/*----------
* Also copy the outer portal's parameter list into the inner portal's
* memory context. We want to pass down the parameter values in case we
* had a command like
* DECLARE c CURSOR FOR SELECT ... WHERE foo = $1
* This will have been parsed using the outer parameter set and the
* parameter value needs to be preserved for use when the cursor is
* executed.
*----------
*/
params = copyParamList(params);
MemoryContextSwitchTo(oldContext);
/*
* Set up options for portal.
*
* If the user didn't specify a SCROLL type, allow or disallow scrolling
* based on whether it would require any additional runtime overhead to do
* so. Also, we disallow scrolling for FOR UPDATE cursors.
*/
portal->cursorOptions = cstmt->options;
if (!(portal->cursorOptions & (CURSOR_OPT_SCROLL | CURSOR_OPT_NO_SCROLL)))
{
if (stmt->rowMarks == NIL &&
ExecSupportsBackwardScan(stmt->planTree))
portal->cursorOptions |= CURSOR_OPT_SCROLL;
else
portal->cursorOptions |= CURSOR_OPT_NO_SCROLL;
}
/*
* Start execution, inserting parameters if any.
*/
PortalStart(portal, params, GetActiveSnapshot());
Assert(portal->strategy == PORTAL_ONE_SELECT);
/*
* We're done; the query won't actually be run until PerformPortalFetch is
* called.
*/
}
/*
* PerformCursorOpen
* Execute SQL DECLARE CURSOR command.
*/
void
PerformCursorOpen(PlannedStmt *stmt, ParamListInfo params,
const char *queryString, bool isTopLevel)
{
DeclareCursorStmt *cstmt = (DeclareCursorStmt *) stmt->utilityStmt;
Portal portal;
MemoryContext oldContext;
if (cstmt == NULL || !IsA(cstmt, DeclareCursorStmt))
elog(ERROR, "PerformCursorOpen called for non-cursor query");
/*
* Disallow empty-string cursor name (conflicts with protocol-level
* unnamed portal).
*/
if (!cstmt->portalname || cstmt->portalname[0] == '\0')
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_NAME),
errmsg("invalid cursor name: must not be empty")));
/*
* If this is a non-holdable cursor, we require that this statement has
* been executed inside a transaction block (or else, it would have no
* user-visible effect).
*/
if (!(cstmt->options & CURSOR_OPT_HOLD))
RequireTransactionChain((void *) cstmt, "DECLARE CURSOR");
/*
* Allow using the SCROLL keyword even though we don't support its
* functionality (backward scrolling). Silently accept it and instead
* of reporting an error like before, override it to NO SCROLL.
*
* for information see: MPP-5305 and BIT-93
*/
if (cstmt->options & CURSOR_OPT_SCROLL)
{
/*ereport(ERROR,
(errcode(ERRCODE_GP_FEATURE_NOT_YET),
errmsg("scrollable cursors are not yet supported in Greenplum Database")));*/
cstmt->options -= CURSOR_OPT_SCROLL;
}
cstmt->options |= CURSOR_OPT_NO_SCROLL;
Assert(!(cstmt->options & CURSOR_OPT_SCROLL && cstmt->options & CURSOR_OPT_NO_SCROLL));
/*
* Create a portal and copy the plan and queryString into its memory.
*/
portal = CreatePortal(cstmt->portalname, false, false);
oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
stmt = copyObject(stmt);
stmt->utilityStmt = NULL; /* make it look like plain SELECT */
stmt->qdContext = PortalGetHeapMemory(portal); /* Temporary! See comment in PlannedStmt. */
queryString = pstrdup(queryString);
PortalDefineQuery(portal,
NULL,
queryString,
T_DeclareCursorStmt,
"SELECT", /* cursor's query is always a SELECT */
list_make1(stmt),
PortalGetHeapMemory(portal));
portal->is_extended_query = true; /* cursors run in extended query mode */
/*
* DeclareCursorStmt is a hybrid utility/select statement. Above, we've nullified
* the utilityStmt within PlannedStmt so this appears like plain SELECT. As a consequence,
* we lose access to the DeclareCursorStmt. To cope, we simply cover over the
* is_simply_updatable calculation for consumption by CURRENT OF constant folding.
*/
portal->is_simply_updatable = cstmt->is_simply_updatable;
/*
* Also copy the outer portal's parameter list into the inner portal's
* memory context. We want to pass down the parameter values in case we
* had a command like DECLARE c CURSOR FOR SELECT ... WHERE foo = $1 This
* will have been parsed using the outer parameter set and the parameter
* value needs to be preserved for use when the cursor is executed.
*/
params = copyParamList(params);
MemoryContextSwitchTo(oldContext);
portal->cursorOptions = cstmt->options;
/*
* Set up options for portal.
*
* If the user didn't specify a SCROLL type, allow or disallow scrolling
* based on whether it would require any additional runtime overhead to do
* so.
*
* GPDB: we do not allow backward scans at the moment regardless
* of any additional runtime overhead. We forced CURSOR_OPT_NO_SCROLL
* above. Comment out this logic.
*/
/*
if (!(portal->cursorOptions & (CURSOR_OPT_SCROLL | CURSOR_OPT_NO_SCROLL)))
{
if (ExecSupportsBackwardScan(plan))
portal->cursorOptions |= CURSOR_OPT_SCROLL;
else
portal->cursorOptions |= CURSOR_OPT_NO_SCROLL;
}
*/
/*
* Start execution, inserting parameters if any.
*/
PortalStart(portal, params, ActiveSnapshot,
savedSeqServerHost, savedSeqServerPort);
Assert(portal->strategy == PORTAL_ONE_SELECT);
/*
* We're done; the query won't actually be run until PerformPortalFetch is
* called.
*/
}
/*
* SPI_cursor_open()
*
* Open a prepared SPI plan as a portal
*/
Portal
SPI_cursor_open(const char *name, void *plan,
Datum *Values, const char *Nulls,
bool read_only)
{
_SPI_plan *spiplan = (_SPI_plan *) plan;
List *qtlist = spiplan->qtlist;
List *ptlist = spiplan->ptlist;
Query *queryTree;
Plan *planTree;
ParamListInfo paramLI;
Snapshot snapshot;
MemoryContext oldcontext;
Portal portal;
int k;
/* Ensure that the plan contains only one query */
if (list_length(ptlist) != 1 || list_length(qtlist) != 1)
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_DEFINITION),
errmsg("cannot open multi-query plan as cursor")));
queryTree = (Query *) linitial((List *) linitial(qtlist));
planTree = (Plan *) linitial(ptlist);
/* Must be a query that returns tuples */
switch (queryTree->commandType)
{
case CMD_SELECT:
if (queryTree->into != NULL)
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_DEFINITION),
errmsg("cannot open SELECT INTO query as cursor")));
break;
case CMD_UTILITY:
if (!UtilityReturnsTuples(queryTree->utilityStmt))
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_DEFINITION),
errmsg("cannot open non-SELECT query as cursor")));
break;
default:
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_DEFINITION),
errmsg("cannot open non-SELECT query as cursor")));
break;
}
/* Reset SPI result */
SPI_processed = 0;
SPI_tuptable = NULL;
_SPI_current->processed = 0;
_SPI_current->tuptable = NULL;
/* Create the portal */
if (name == NULL || name[0] == '\0')
{
/* Use a random nonconflicting name */
portal = CreateNewPortal();
}
else
{
/* In this path, error if portal of same name already exists */
portal = CreatePortal(name, false, false);
}
/* Switch to portals memory and copy the parsetree and plan to there */
oldcontext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
queryTree = copyObject(queryTree);
planTree = copyObject(planTree);
/* If the plan has parameters, set them up */
if (spiplan->nargs > 0)
{
paramLI = (ParamListInfo) palloc0((spiplan->nargs + 1) *
sizeof(ParamListInfoData));
for (k = 0; k < spiplan->nargs; k++)
{
paramLI[k].kind = PARAM_NUM;
paramLI[k].id = k + 1;
paramLI[k].ptype = spiplan->argtypes[k];
paramLI[k].isnull = (Nulls && Nulls[k] == 'n');
if (paramLI[k].isnull)
{
/* nulls just copy */
paramLI[k].value = Values[k];
}
else
{
/* pass-by-ref values must be copied into portal context */
int16 paramTypLen;
bool paramTypByVal;
get_typlenbyval(spiplan->argtypes[k],
¶mTypLen, ¶mTypByVal);
paramLI[k].value = datumCopy(Values[k],
paramTypByVal, paramTypLen);
}
}
paramLI[k].kind = PARAM_INVALID;
}
else
paramLI = NULL;
/*
* Set up the portal.
*/
PortalDefineQuery(portal,
NULL, /* unfortunately don't have sourceText */
"SELECT", /* nor the raw parse tree... */
list_make1(queryTree),
list_make1(planTree),
PortalGetHeapMemory(portal));
MemoryContextSwitchTo(oldcontext);
/*
* Set up options for portal.
*/
portal->cursorOptions &= ~(CURSOR_OPT_SCROLL | CURSOR_OPT_NO_SCROLL);
if (planTree == NULL || ExecSupportsBackwardScan(planTree))
portal->cursorOptions |= CURSOR_OPT_SCROLL;
else
portal->cursorOptions |= CURSOR_OPT_NO_SCROLL;
/*
* Set up the snapshot to use. (PortalStart will do CopySnapshot,
* so we skip that here.)
*/
if (read_only)
snapshot = ActiveSnapshot;
else
{
CommandCounterIncrement();
snapshot = GetTransactionSnapshot();
}
/*
* Start portal execution.
*/
PortalStart(portal, paramLI, snapshot);
Assert(portal->strategy == PORTAL_ONE_SELECT ||
portal->strategy == PORTAL_UTIL_SELECT);
/* Return the created portal */
return portal;
}
/*
* PerformCursorOpen
* Execute SQL DECLARE CURSOR command.
*/
void
PerformCursorOpen(DeclareCursorStmt *cstmt, ParamListInfo params,
const char *queryString, bool isTopLevel)
{
Query *query = (Query *) cstmt->query;
List *rewritten;
PlannedStmt *plan;
Portal portal;
MemoryContext oldContext;
Assert(IsA(query, Query)); /* else parse analysis wasn't done */
/*
* Disallow empty-string cursor name (conflicts with protocol-level
* unnamed portal).
*/
if (!cstmt->portalname || cstmt->portalname[0] == '\0')
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_NAME),
errmsg("invalid cursor name: must not be empty")));
/*
* If this is a non-holdable cursor, we require that this statement has
* been executed inside a transaction block (or else, it would have no
* user-visible effect).
*/
if (!(cstmt->options & CURSOR_OPT_HOLD))
RequireTransactionChain(isTopLevel, "DECLARE CURSOR");
/*
* Parse analysis was done already, but we still have to run the rule
* rewriter. We do not do AcquireRewriteLocks: we assume the query either
* came straight from the parser, or suitable locks were acquired by
* plancache.c.
*
* Because the rewriter and planner tend to scribble on the input, we make
* a preliminary copy of the source querytree. This prevents problems in
* the case that the DECLARE CURSOR is in a portal or plpgsql function and
* is executed repeatedly. (See also the same hack in EXPLAIN and
* PREPARE.) XXX FIXME someday.
*/
rewritten = QueryRewrite((Query *) copyObject(query));
/* SELECT should never rewrite to more or less than one query */
if (list_length(rewritten) != 1)
elog(ERROR, "non-SELECT statement in DECLARE CURSOR");
query = (Query *) linitial(rewritten);
if (query->commandType != CMD_SELECT)
elog(ERROR, "non-SELECT statement in DECLARE CURSOR");
/* Plan the query, applying the specified options */
plan = pg_plan_query(query, cstmt->options, params);
/*
* Create a portal and copy the plan and queryString into its memory.
*/
portal = CreatePortal(cstmt->portalname, false, false);
oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
plan = copyObject(plan);
queryString = pstrdup(queryString);
PortalDefineQuery(portal,
NULL,
queryString,
"SELECT", /* cursor's query is always a SELECT */
list_make1(plan),
NULL);
/*----------
* Also copy the outer portal's parameter list into the inner portal's
* memory context. We want to pass down the parameter values in case we
* had a command like
* DECLARE c CURSOR FOR SELECT ... WHERE foo = $1
* This will have been parsed using the outer parameter set and the
* parameter value needs to be preserved for use when the cursor is
* executed.
*----------
*/
params = copyParamList(params);
MemoryContextSwitchTo(oldContext);
/*
* Set up options for portal.
*
* If the user didn't specify a SCROLL type, allow or disallow scrolling
* based on whether it would require any additional runtime overhead to do
* so. Also, we disallow scrolling for FOR UPDATE cursors.
*/
portal->cursorOptions = cstmt->options;
if (!(portal->cursorOptions & (CURSOR_OPT_SCROLL | CURSOR_OPT_NO_SCROLL)))
{
if (plan->rowMarks == NIL &&
ExecSupportsBackwardScan(plan->planTree))
portal->cursorOptions |= CURSOR_OPT_SCROLL;
else
portal->cursorOptions |= CURSOR_OPT_NO_SCROLL;
}
/*
* Start execution, inserting parameters if any.
*/
PortalStart(portal, params, 0, GetActiveSnapshot());
Assert(portal->strategy == PORTAL_ONE_SELECT);
/*
* We're done; the query won't actually be run until PerformPortalFetch is
* called.
*/
}
/*
* PerformCursorOpen
* Execute SQL DECLARE CURSOR command.
*/
void
PerformCursorOpen(DeclareCursorStmt *stmt)
{
List *rewritten;
Query *query;
Plan *plan;
Portal portal;
MemoryContext oldContext;
/*
* Disallow empty-string cursor name (conflicts with protocol-level
* unnamed portal).
*/
if (!stmt->portalname || stmt->portalname[0] == '\0')
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_NAME),
errmsg("invalid cursor name: must not be empty")));
/*
* If this is a non-holdable cursor, we require that this statement
* has been executed inside a transaction block (or else, it would
* have no user-visible effect).
*/
if (!(stmt->options & CURSOR_OPT_HOLD))
RequireTransactionChain((void *) stmt, "DECLARE CURSOR");
/*
* Because the planner is not cool about not scribbling on its input,
* we make a preliminary copy of the source querytree. This prevents
* problems in the case that the DECLARE CURSOR is in a portal and is
* executed repeatedly. XXX the planner really shouldn't modify its
* input ... FIXME someday.
*/
query = copyObject(stmt->query);
/*
* The query has been through parse analysis, but not rewriting or
* planning as yet. Note that the grammar ensured we have a SELECT
* query, so we are not expecting rule rewriting to do anything
* strange.
*/
rewritten = QueryRewrite(query);
if (length(rewritten) != 1 || !IsA(lfirst(rewritten), Query))
elog(ERROR, "unexpected rewrite result");
query = (Query *) lfirst(rewritten);
if (query->commandType != CMD_SELECT)
elog(ERROR, "unexpected rewrite result");
if (query->into)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("DECLARE CURSOR may not specify INTO")));
if (query->rowMarks != NIL)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("DECLARE CURSOR ... FOR UPDATE is not supported"),
errdetail("Cursors must be READ ONLY.")));
plan = planner(query, true, stmt->options);
/*
* Create a portal and copy the query and plan into its memory
* context.
*/
portal = CreatePortal(stmt->portalname, false, false);
oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
query = copyObject(query);
plan = copyObject(plan);
PortalDefineQuery(portal,
NULL, /* unfortunately don't have sourceText */
"SELECT", /* cursor's query is always a SELECT */
makeList1(query),
makeList1(plan),
PortalGetHeapMemory(portal));
MemoryContextSwitchTo(oldContext);
/*
* Set up options for portal.
*
* If the user didn't specify a SCROLL type, allow or disallow scrolling
* based on whether it would require any additional runtime overhead
* to do so.
*/
portal->cursorOptions = stmt->options;
if (!(portal->cursorOptions & (CURSOR_OPT_SCROLL | CURSOR_OPT_NO_SCROLL)))
{
if (ExecSupportsBackwardScan(plan))
portal->cursorOptions |= CURSOR_OPT_SCROLL;
else
portal->cursorOptions |= CURSOR_OPT_NO_SCROLL;
}
/*
* Start execution --- never any params for a cursor.
*/
PortalStart(portal, NULL);
Assert(portal->strategy == PORTAL_ONE_SELECT);
/*
* We're done; the query won't actually be run until
* PerformPortalFetch is called.
*/
}