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Change representation of statement lists, and add statement location info.

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This patch makes several changes that improve the consistency of
representation of lists of statements.  It's always been the case
that the output of parse analysis is a list of Query nodes, whatever
the types of the individual statements in the list.  This patch brings
similar consistency to the outputs of raw parsing and planning steps:

* The output of raw parsing is now always a list of RawStmt nodes;
the statement-type-dependent nodes are one level down from that.

* The output of pg_plan_queries() is now always a list of PlannedStmt
nodes, even for utility statements.  In the case of a utility statement,
"planning" just consists of wrapping a CMD_UTILITY PlannedStmt around
the utility node.  This list representation is now used in Portal and
CachedPlan plan lists, replacing the former convention of intermixing
PlannedStmts with bare utility-statement nodes.

Now, every list of statements has a consistent head-node type depending
on how far along it is in processing.  This allows changing many places
that formerly used generic "Node *" pointers to use a more specific
pointer type, thus reducing the number of IsA() tests and casts needed,
as well as improving code clarity.

Also, the post-parse-analysis representation of DECLARE CURSOR is changed
so that it looks more like EXPLAIN, PREPARE, etc.  That is, the contained
SELECT remains a child of the DeclareCursorStmt rather than getting flipped
around to be the other way.  It's now true for both Query and PlannedStmt
that utilityStmt is non-null if and only if commandType is CMD_UTILITY.
That allows simplifying a lot of places that were testing both fields.
(I think some of those were just defensive programming, but in many places,
it was actually necessary to avoid confusing DECLARE CURSOR with SELECT.)

Because PlannedStmt carries a canSetTag field, we're also able to get rid
of some ad-hoc rules about how to reconstruct canSetTag for a bare utility
statement; specifically, the assumption that a utility is canSetTag if and
only if it's the only one in its list.  While I see no near-term need for
relaxing that restriction, it's nice to get rid of the ad-hocery.

The API of ProcessUtility() is changed so that what it's passed is the
wrapper PlannedStmt not just the bare utility statement.  This will affect
all users of ProcessUtility_hook, but the changes are pretty trivial; see
the affected contrib modules for examples of the minimum change needed.
(Most compilers should give pointer-type-mismatch warnings for uncorrected
code.)

There's also a change in the API of ExplainOneQuery_hook, to pass through
cursorOptions instead of expecting hook functions to know what to pick.
This is needed because of the DECLARE CURSOR changes, but really should
have been done in 9.6; it's unlikely that any extant hook functions
know about using CURSOR_OPT_PARALLEL_OK.

Finally, teach gram.y to save statement boundary locations in RawStmt
nodes, and pass those through to Query and PlannedStmt nodes.  This allows
more intelligent handling of cases where a source query string contains
multiple statements.  This patch doesn't actually do anything with the
information, but a follow-on patch will.  (Passing this information through
cleanly is the true motivation for these changes; while I think this is all
good cleanup, it's unlikely we'd have bothered without this end goal.)

catversion bump because addition of location fields to struct Query
affects stored rules.

This patch is by me, but it owes a good deal to Fabien Coelho who did
a lot of preliminary work on the problem, and also reviewed the patch.

Discussion: https://postgr.es/m/alpine.DEB.2.20.1612200926310.29821@lancre
This commit is contained in:
Tom Lane
2017-01-14 16:02:35 -05:00
parent 75abb955df
commit ab1f0c8225
53 changed files with 788 additions and 547 deletions
Download Patch File Download Diff File Expand all files Collapse all files

132
src/backend/tcop/pquery.c
View File

@@ -43,7 +43,7 @@ static uint64 RunFromStore(Portal portal, ScanDirection direction, uint64 count,
DestReceiver *dest);
static uint64 PortalRunSelect(Portal portal, bool forward, long count,
DestReceiver *dest);
static void PortalRunUtility(Portal portal, Node *utilityStmt,
static void PortalRunUtility(Portal portal, PlannedStmt *pstmt,
bool isTopLevel, bool setHoldSnapshot,
DestReceiver *dest, char *completionTag);
static void PortalRunMulti(Portal portal,
@@ -73,7 +73,6 @@ CreateQueryDesc(PlannedStmt *plannedstmt,
qd->operation = plannedstmt->commandType; /* operation */
qd->plannedstmt = plannedstmt; /* plan */
qd->utilitystmt = plannedstmt->utilityStmt; /* in case DECLARE CURSOR */
qd->sourceText = sourceText; /* query text */
qd->snapshot = RegisterSnapshot(snapshot); /* snapshot */
/* RI check snapshot */
@@ -92,37 +91,6 @@ CreateQueryDesc(PlannedStmt *plannedstmt,
return qd;
}
/*
* CreateUtilityQueryDesc
*/
QueryDesc *
CreateUtilityQueryDesc(Node *utilitystmt,
const char *sourceText,
Snapshot snapshot,
DestReceiver *dest,
ParamListInfo params)
{
QueryDesc *qd = (QueryDesc *) palloc(sizeof(QueryDesc));
qd->operation = CMD_UTILITY; /* operation */
qd->plannedstmt = NULL;
qd->utilitystmt = utilitystmt; /* utility command */
qd->sourceText = sourceText; /* query text */
qd->snapshot = RegisterSnapshot(snapshot); /* snapshot */
qd->crosscheck_snapshot = InvalidSnapshot; /* RI check snapshot */
qd->dest = dest; /* output dest */
qd->params = params; /* parameter values passed into query */
qd->instrument_options = false; /* uninteresting for utilities */
/* null these fields until set by ExecutorStart */
qd->tupDesc = NULL;
qd->estate = NULL;
qd->planstate = NULL;
qd->totaltime = NULL;
return qd;
}
/*
* FreeQueryDesc
*/
@@ -236,7 +204,7 @@ ProcessQuery(PlannedStmt *plan,
* ChoosePortalStrategy
* Select portal execution strategy given the intended statement list.
*
* The list elements can be Querys, PlannedStmts, or utility statements.
* The list elements can be Querys or PlannedStmts.
* That's more general than portals need, but plancache.c uses this too.
*
* See the comments in portal.h.
@@ -263,16 +231,14 @@ ChoosePortalStrategy(List *stmts)
if (query->canSetTag)
{
if (query->commandType == CMD_SELECT &&
query->utilityStmt == NULL)
if (query->commandType == CMD_SELECT)
{
if (query->hasModifyingCTE)
return PORTAL_ONE_MOD_WITH;
else
return PORTAL_ONE_SELECT;
}
if (query->commandType == CMD_UTILITY &&
query->utilityStmt != NULL)
if (query->commandType == CMD_UTILITY)
{
if (UtilityReturnsTuples(query->utilityStmt))
return PORTAL_UTIL_SELECT;
@@ -287,24 +253,24 @@ ChoosePortalStrategy(List *stmts)
if (pstmt->canSetTag)
{
if (pstmt->commandType == CMD_SELECT &&
pstmt->utilityStmt == NULL)
if (pstmt->commandType == CMD_SELECT)
{
if (pstmt->hasModifyingCTE)
return PORTAL_ONE_MOD_WITH;
else
return PORTAL_ONE_SELECT;
}
if (pstmt->commandType == CMD_UTILITY)
{
if (UtilityReturnsTuples(pstmt->utilityStmt))
return PORTAL_UTIL_SELECT;
/* it can't be ONE_RETURNING, so give up */
return PORTAL_MULTI_QUERY;
}
}
}
else
{
/* must be a utility command; assume it's canSetTag */
if (UtilityReturnsTuples(stmt))
return PORTAL_UTIL_SELECT;
/* it can't be ONE_RETURNING, so give up */
return PORTAL_MULTI_QUERY;
}
elog(ERROR, "unrecognized node type: %d", (int) nodeTag(stmt));
}
/*
@@ -325,7 +291,8 @@ ChoosePortalStrategy(List *stmts)
{
if (++nSetTag > 1)
return PORTAL_MULTI_QUERY; /* no need to look further */
if (query->returningList == NIL)
if (query->commandType == CMD_UTILITY ||
query->returningList == NIL)
return PORTAL_MULTI_QUERY; /* no need to look further */
}
}
@@ -337,11 +304,13 @@ ChoosePortalStrategy(List *stmts)
{
if (++nSetTag > 1)
return PORTAL_MULTI_QUERY; /* no need to look further */
if (!pstmt->hasReturning)
if (pstmt->commandType == CMD_UTILITY ||
!pstmt->hasReturning)
return PORTAL_MULTI_QUERY; /* no need to look further */
}
}
/* otherwise, utility command, assumed not canSetTag */
else
elog(ERROR, "unrecognized node type: %d", (int) nodeTag(stmt));
}
if (nSetTag == 1)
return PORTAL_ONE_RETURNING;
@@ -364,7 +333,7 @@ FetchPortalTargetList(Portal portal)
if (portal->strategy == PORTAL_MULTI_QUERY)
return NIL;
/* get the primary statement and find out what it returns */
return FetchStatementTargetList(PortalGetPrimaryStmt(portal));
return FetchStatementTargetList((Node *) PortalGetPrimaryStmt(portal));
}
/*
@@ -372,7 +341,7 @@ FetchPortalTargetList(Portal portal)
* Given a statement that returns tuples, extract the query targetlist.
* Returns NIL if the statement doesn't have a determinable targetlist.
*
* This can be applied to a Query, a PlannedStmt, or a utility statement.
* This can be applied to a Query or a PlannedStmt.
* That's more general than portals need, but plancache.c uses this too.
*
* Note: do not modify the result.
@@ -388,16 +357,14 @@ FetchStatementTargetList(Node *stmt)
{
Query *query = (Query *) stmt;
if (query->commandType == CMD_UTILITY &&
query->utilityStmt != NULL)
if (query->commandType == CMD_UTILITY)
{
/* transfer attention to utility statement */
stmt = query->utilityStmt;
}
else
{
if (query->commandType == CMD_SELECT &&
query->utilityStmt == NULL)
if (query->commandType == CMD_SELECT)
return query->targetList;
if (query->returningList)
return query->returningList;
@@ -408,12 +375,19 @@ FetchStatementTargetList(Node *stmt)
{
PlannedStmt *pstmt = (PlannedStmt *) stmt;
if (pstmt->commandType == CMD_SELECT &&
pstmt->utilityStmt == NULL)
return pstmt->planTree->targetlist;
if (pstmt->hasReturning)
return pstmt->planTree->targetlist;
return NIL;
if (pstmt->commandType == CMD_UTILITY)
{
/* transfer attention to utility statement */
stmt = pstmt->utilityStmt;
}
else
{
if (pstmt->commandType == CMD_SELECT)
return pstmt->planTree->targetlist;
if (pstmt->hasReturning)
return pstmt->planTree->targetlist;
return NIL;
}
}
if (IsA(stmt, FetchStmt))
{
@@ -566,8 +540,7 @@ PortalStart(Portal portal, ParamListInfo params,
{
PlannedStmt *pstmt;
pstmt = (PlannedStmt *) PortalGetPrimaryStmt(portal);
Assert(IsA(pstmt, PlannedStmt));
pstmt = PortalGetPrimaryStmt(portal);
portal->tupDesc =
ExecCleanTypeFromTL(pstmt->planTree->targetlist,
false);
@@ -588,10 +561,10 @@ PortalStart(Portal portal, ParamListInfo params,
* take care of it if needed.
*/
{
Node *ustmt = PortalGetPrimaryStmt(portal);
PlannedStmt *pstmt = PortalGetPrimaryStmt(portal);
Assert(!IsA(ustmt, PlannedStmt));
portal->tupDesc = UtilityTupleDescriptor(ustmt);
Assert(pstmt->commandType == CMD_UTILITY);
portal->tupDesc = UtilityTupleDescriptor(pstmt->utilityStmt);
}
/*
@@ -1047,7 +1020,7 @@ FillPortalStore(Portal portal, bool isTopLevel)
break;
case PORTAL_UTIL_SELECT:
PortalRunUtility(portal, (Node *) linitial(portal->stmts),
PortalRunUtility(portal, (PlannedStmt *) linitial(portal->stmts),
isTopLevel, true, treceiver, completionTag);
break;
@@ -1143,10 +1116,11 @@ RunFromStore(Portal portal, ScanDirection direction, uint64 count,
* Execute a utility statement inside a portal.
*/
static void
PortalRunUtility(Portal portal, Node *utilityStmt,
PortalRunUtility(Portal portal, PlannedStmt *pstmt,
bool isTopLevel, bool setHoldSnapshot,
DestReceiver *dest, char *completionTag)
{
Node *utilityStmt = pstmt->utilityStmt;
Snapshot snapshot;
/*
@@ -1186,7 +1160,7 @@ PortalRunUtility(Portal portal, Node *utilityStmt,
else
snapshot = NULL;
ProcessUtility(utilityStmt,
ProcessUtility(pstmt,
portal->sourceText,
isTopLevel ? PROCESS_UTILITY_TOPLEVEL : PROCESS_UTILITY_QUERY,
portal->portalParams,
@@ -1241,21 +1215,18 @@ PortalRunMulti(Portal portal,
*/
foreach(stmtlist_item, portal->stmts)
{
Node *stmt = (Node *) lfirst(stmtlist_item);
PlannedStmt *pstmt = (PlannedStmt *) lfirst(stmtlist_item);
/*
* If we got a cancel signal in prior command, quit
*/
CHECK_FOR_INTERRUPTS();
if (IsA(stmt, PlannedStmt) &&
((PlannedStmt *) stmt)->utilityStmt == NULL)
if (pstmt->utilityStmt == NULL)
{
/*
* process a plannable query.
*/
PlannedStmt *pstmt = (PlannedStmt *) stmt;
TRACE_POSTGRESQL_QUERY_EXECUTE_START();
if (log_executor_stats)
@@ -1320,9 +1291,6 @@ PortalRunMulti(Portal portal,
/*
* process utility functions (create, destroy, etc..)
*
* These are assumed canSetTag if they're the only stmt in the
* portal.
*
* We must not set a snapshot here for utility commands (if one is
* needed, PortalRunUtility will do it). If a utility command is
* alone in a portal then everything's fine. The only case where
@@ -1331,18 +1299,18 @@ PortalRunMulti(Portal portal,
* whether it has a snapshot or not, so we just leave the current
* snapshot alone if we have one.
*/
if (list_length(portal->stmts) == 1)
if (pstmt->canSetTag)
{
Assert(!active_snapshot_set);
/* statement can set tag string */
PortalRunUtility(portal, stmt, isTopLevel, false,
PortalRunUtility(portal, pstmt, isTopLevel, false,
dest, completionTag);
}
else
{
Assert(IsA(stmt, NotifyStmt));
Assert(IsA(pstmt->utilityStmt, NotifyStmt));
/* stmt added by rewrite cannot set tag */
PortalRunUtility(portal, stmt, isTopLevel, false,
PortalRunUtility(portal, pstmt, isTopLevel, false,
altdest, NULL);
}
}