/** ChoosePortalStrategy*        Select portal execution strategy given the intended statement list.** The list elements can be Querys, PlannedStmts, or utility statements.* That's more general than portals need, but plancache.c uses this too.** See the comments in portal.h.*/
PortalStrategy
ChoosePortalStrategy(List *stmts)
{int            nSetTag;ListCell   *lc;/** PORTAL_ONE_SELECT and PORTAL_UTIL_SELECT need only consider the* single-statement case, since there are no rewrite rules that can add* auxiliary queries to a SELECT or a utility command. PORTAL_ONE_MOD_WITH* likewise allows only one top-level statement.*/if (list_length(stmts) == 1){Node       *stmt = (Node *) linitial(stmts);if (IsA(stmt, Query)){Query       *query = (Query *) stmt;if (query->canSetTag){if (query->commandType == CMD_SELECT &&query->utilityStmt == NULL){if (query->hasModifyingCTE)return PORTAL_ONE_MOD_WITH;elsereturn PORTAL_ONE_SELECT;}if (query->commandType == CMD_UTILITY &&query->utilityStmt != NULL){if (UtilityReturnsTuples(query->utilityStmt))return PORTAL_UTIL_SELECT;/* it can't be ONE_RETURNING, so give up */return PORTAL_MULTI_QUERY;}}}else if (IsA(stmt, PlannedStmt)){PlannedStmt *pstmt = (PlannedStmt *) stmt;if (pstmt->canSetTag){if (pstmt->commandType == CMD_SELECT &&pstmt->utilityStmt == NULL){if (pstmt->hasModifyingCTE)return PORTAL_ONE_MOD_WITH;elsereturn PORTAL_ONE_SELECT;}}}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;}}/** PORTAL_ONE_RETURNING has to allow auxiliary queries added by rewrite.* Choose PORTAL_ONE_RETURNING if there is exactly one canSetTag query and* it has a RETURNING list.*/nSetTag = 0;foreach(lc, stmts){Node       *stmt = (Node *) lfirst(lc);if (IsA(stmt, Query)){Query       *query = (Query *) stmt;if (query->canSetTag){if (++nSetTag > 1)return PORTAL_MULTI_QUERY;    /* no need to look further */if (query->returningList == NIL)return PORTAL_MULTI_QUERY;    /* no need to look further */}}else if (IsA(stmt, PlannedStmt)){PlannedStmt *pstmt = (PlannedStmt *) stmt;if (pstmt->canSetTag){if (++nSetTag > 1)return PORTAL_MULTI_QUERY;    /* no need to look further */if (!pstmt->hasReturning)return PORTAL_MULTI_QUERY;    /* no need to look further */}}/* otherwise, utility command, assumed not canSetTag */}if (nSetTag == 1)return PORTAL_ONE_RETURNING;/* Else, it's the general case... */return PORTAL_MULTI_QUERY;
}

static inline int
list_length(const List *l)
{return l ? l->length : 0;
}

#define lfirst(lc)                 ((lc)->data.ptr_value)

#define linitial(l)                lfirst(list_head(l))

static inline ListCell *
list_head(const List *l)
{return l ? l->head : NULL;
}