/*------------------------------------------------------------------------- * * nodeMergejoin.c * routines supporting merge joins * * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * src/backend/executor/nodeMergejoin.c * *------------------------------------------------------------------------- */ /* * INTERFACE ROUTINES * ExecMergeJoin mergejoin outer and inner relations. * ExecInitMergeJoin creates and initializes run time states * ExecEndMergeJoin cleans up the node. * * NOTES * * Merge-join is done by joining the inner and outer tuples satisfying * join clauses of the form ((= outerKey innerKey) ...). * The join clause list is provided by the query planner and may contain * more than one (= outerKey innerKey) clause (for composite sort key). * * However, the query executor needs to know whether an outer * tuple is "greater/smaller" than an inner tuple so that it can * "synchronize" the two relations. For example, consider the following * relations: * * outer: (0 ^1 1 2 5 5 5 6 6 7) current tuple: 1 * inner: (1 ^3 5 5 5 5 6) current tuple: 3 * * To continue the merge-join, the executor needs to scan both inner * and outer relations till the matching tuples 5. It needs to know * that currently inner tuple 3 is "greater" than outer tuple 1 and * therefore it should scan the outer relation first to find a * matching tuple and so on. * * Therefore, rather than directly executing the merge join clauses, * we evaluate the left and right key expressions separately and then * compare the columns one at a time (see MJCompare). The planner * passes us enough information about the sort ordering of the inputs * to allow us to determine how to make the comparison. We may use the * appropriate btree comparison function, since Postgres' only notion * of ordering is specified by btree opfamilies. * * * Consider the above relations and suppose that the executor has * just joined the first outer "5" with the last inner "5". The * next step is of course to join the second outer "5" with all * the inner "5's". This requires repositioning the inner "cursor" * to point at the first inner "5". This is done by "marking" the * first inner 5 so we can restore the "cursor" to it before joining * with the second outer 5. The access method interface provides * routines to mark and restore to a tuple. * * * Essential operation of the merge join algorithm is as follows: * * Join { * get initial outer and inner tuples INITIALIZE * do forever { * while (outer != inner) { SKIP_TEST * if (outer < inner) * advance outer SKIPOUTER_ADVANCE * else * advance inner SKIPINNER_ADVANCE * } * mark inner position SKIP_TEST * do forever { * while (outer == inner) { * join tuples JOINTUPLES * advance inner position NEXTINNER * } * advance outer position NEXTOUTER * if (outer == mark) TESTOUTER * restore inner position to mark TESTOUTER * else * break // return to top of outer loop * } * } * } * * The merge join operation is coded in the fashion * of a state machine. At each state, we do something and then * proceed to another state. This state is stored in the node's * execution state information and is preserved across calls to * ExecMergeJoin. -cim 10/31/89 */ #include "postgres.h" #include "access/nbtree.h" #include "executor/execdebug.h" #include "executor/nodeMergejoin.h" #include "miscadmin.h" #include "utils/lsyscache.h" #include "utils/memutils.h" /* * States of the ExecMergeJoin state machine */ #define EXEC_MJ_INITIALIZE_OUTER 1 #define EXEC_MJ_INITIALIZE_INNER 2 #define EXEC_MJ_JOINTUPLES 3 #define EXEC_MJ_NEXTOUTER 4 #define EXEC_MJ_TESTOUTER 5 #define EXEC_MJ_NEXTINNER 6 #define EXEC_MJ_SKIP_TEST 7 #define EXEC_MJ_SKIPOUTER_ADVANCE 8 #define EXEC_MJ_SKIPINNER_ADVANCE 9 #define EXEC_MJ_ENDOUTER 10 #define EXEC_MJ_ENDINNER 11 /* * Runtime data for each mergejoin clause */ typedef struct MergeJoinClauseData { /* Executable expression trees */ ExprState *lexpr; /* left-hand (outer) input expression */ ExprState *rexpr; /* right-hand (inner) input expression */ /* * If we have a current left or right input tuple, the values of the * expressions are loaded into these fields: */ Datum ldatum; /* current left-hand value */ Datum rdatum; /* current right-hand value */ bool lisnull; /* and their isnull flags */ bool risnull; /* * Everything we need to know to compare the left and right values is * stored here. */ SortSupportData ssup; } MergeJoinClauseData; /* Result type for MJEvalOuterValues and MJEvalInnerValues */ typedef enum { MJEVAL_MATCHABLE, /* normal, potentially matchable tuple */ MJEVAL_NONMATCHABLE, /* tuple cannot join because it has a null */ MJEVAL_ENDOFJOIN /* end of input (physical or effective) */ } MJEvalResult; #define MarkInnerTuple(innerTupleSlot, mergestate) \ ExecCopySlot((mergestate)->mj_MarkedTupleSlot, (innerTupleSlot)) /* * MJExamineQuals * * This deconstructs the list of mergejoinable expressions, which is given * to us by the planner in the form of a list of "leftexpr = rightexpr" * expression trees in the order matching the sort columns of the inputs. * We build an array of MergeJoinClause structs containing the information * we will need at runtime. Each struct essentially tells us how to compare * the two expressions from the original clause. * * In addition to the expressions themselves, the planner passes the btree * opfamily OID, collation OID, btree strategy number (BTLessStrategyNumber or * BTGreaterStrategyNumber), and nulls-first flag that identify the intended * sort ordering for each merge key. The mergejoinable operator is an * equality operator in the opfamily, and the two inputs are guaranteed to be * ordered in either increasing or decreasing (respectively) order according * to the opfamily and collation, with nulls at the indicated end of the range. * This allows us to obtain the needed comparison function from the opfamily. */ static MergeJoinClause MJExamineQuals(List *mergeclauses, Oid *mergefamilies, Oid *mergecollations, int *mergestrategies, bool *mergenullsfirst, PlanState *parent) { MergeJoinClause clauses; int nClauses = list_length(mergeclauses); int iClause; ListCell *cl; clauses = (MergeJoinClause) palloc0(nClauses * sizeof(MergeJoinClauseData)); iClause = 0; foreach(cl, mergeclauses) { OpExpr *qual = (OpExpr *) lfirst(cl); MergeJoinClause clause = &clauses[iClause]; Oid opfamily = mergefamilies[iClause]; Oid collation = mergecollations[iClause]; StrategyNumber opstrategy = mergestrategies[iClause]; bool nulls_first = mergenullsfirst[iClause]; int op_strategy; Oid op_lefttype; Oid op_righttype; Oid sortfunc; if (!IsA(qual, OpExpr)) elog(ERROR, "mergejoin clause is not an OpExpr"); /* * Prepare the input expressions for execution. */ clause->lexpr = ExecInitExpr((Expr *) linitial(qual->args), parent); clause->rexpr = ExecInitExpr((Expr *) lsecond(qual->args), parent); /* Set up sort support data */ clause->ssup.ssup_cxt = CurrentMemoryContext; clause->ssup.ssup_collation = collation; if (opstrategy == BTLessStrategyNumber) clause->ssup.ssup_reverse = false; else if (opstrategy == BTGreaterStrategyNumber) clause->ssup.ssup_reverse = true; else /* planner screwed up */ elog(ERROR, "unsupported mergejoin strategy %d", opstrategy); clause->ssup.ssup_nulls_first = nulls_first; /* Extract the operator's declared left/right datatypes */ get_op_opfamily_properties(qual->opno, opfamily, false, &op_strategy, &op_lefttype, &op_righttype); if (op_strategy != BTEqualStrategyNumber) /* should not happen */ elog(ERROR, "cannot merge using non-equality operator %u", qual->opno); /* * sortsupport routine must know if abbreviation optimization is * applicable in principle. It is never applicable for merge joins * because there is no convenient opportunity to convert to * alternative representation. */ clause->ssup.abbreviate = false; /* And get the matching support or comparison function */ Assert(clause->ssup.comparator == NULL); sortfunc = get_opfamily_proc(opfamily, op_lefttype, op_righttype, BTSORTSUPPORT_PROC); if (OidIsValid(sortfunc)) { /* The sort support function can provide a comparator */ OidFunctionCall1(sortfunc, PointerGetDatum(&clause->ssup)); } if (clause->ssup.comparator == NULL) { /* support not available, get comparison func */ sortfunc = get_opfamily_proc(opfamily, op_lefttype, op_righttype, BTORDER_PROC); if (!OidIsValid(sortfunc)) /* should not happen */ elog(ERROR, "missing support function %d(%u,%u) in opfamily %u", BTORDER_PROC, op_lefttype, op_righttype, opfamily); /* We'll use a shim to call the old-style btree comparator */ PrepareSortSupportComparisonShim(sortfunc, &clause->ssup); } iClause++; } return clauses; } /* * MJEvalOuterValues * * Compute the values of the mergejoined expressions for the current * outer tuple. We also detect whether it's impossible for the current * outer tuple to match anything --- this is true if it yields a NULL * input, since we assume mergejoin operators are strict. If the NULL * is in the first join column, and that column sorts nulls last, then * we can further conclude that no following tuple can match anything * either, since they must all have nulls in the first column. However, * that case is only interesting if we're not in FillOuter mode, else * we have to visit all the tuples anyway. * * For the convenience of callers, we also make this routine responsible * for testing for end-of-input (null outer tuple), and returning * MJEVAL_ENDOFJOIN when that's seen. This allows the same code to be used * for both real end-of-input and the effective end-of-input represented by * a first-column NULL. * * We evaluate the values in OuterEContext, which can be reset each * time we move to a new tuple. */ static MJEvalResult MJEvalOuterValues(MergeJoinState *mergestate) { ExprContext *econtext = mergestate->mj_OuterEContext; MJEvalResult result = MJEVAL_MATCHABLE; int i; MemoryContext oldContext; /* Check for end of outer subplan */ if (TupIsNull(mergestate->mj_OuterTupleSlot)) return MJEVAL_ENDOFJOIN; ResetExprContext(econtext); oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory); econtext->ecxt_outertuple = mergestate->mj_OuterTupleSlot; for (i = 0; i < mergestate->mj_NumClauses; i++) { MergeJoinClause clause = &mergestate->mj_Clauses[i]; clause->ldatum = ExecEvalExpr(clause->lexpr, econtext, &clause->lisnull); if (clause->lisnull) { /* match is impossible; can we end the join early? */ if (i == 0 && !clause->ssup.ssup_nulls_first && !mergestate->mj_FillOuter) result = MJEVAL_ENDOFJOIN; else if (result == MJEVAL_MATCHABLE) result = MJEVAL_NONMATCHABLE; } } MemoryContextSwitchTo(oldContext); return result; } /* * MJEvalInnerValues * * Same as above, but for the inner tuple. Here, we have to be prepared * to load data from either the true current inner, or the marked inner, * so caller must tell us which slot to load from. */ static MJEvalResult MJEvalInnerValues(MergeJoinState *mergestate, TupleTableSlot *innerslot) { ExprContext *econtext = mergestate->mj_InnerEContext; MJEvalResult result = MJEVAL_MATCHABLE; int i; MemoryContext oldContext; /* Check for end of inner subplan */ if (TupIsNull(innerslot)) return MJEVAL_ENDOFJOIN; ResetExprContext(econtext); oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory); econtext->ecxt_innertuple = innerslot; for (i = 0; i < mergestate->mj_NumClauses; i++) { MergeJoinClause clause = &mergestate->mj_Clauses[i]; clause->rdatum = ExecEvalExpr(clause->rexpr, econtext, &clause->risnull); if (clause->risnull) { /* match is impossible; can we end the join early? */ if (i == 0 && !clause->ssup.ssup_nulls_first && !mergestate->mj_FillInner) result = MJEVAL_ENDOFJOIN; else if (result == MJEVAL_MATCHABLE) result = MJEVAL_NONMATCHABLE; } } MemoryContextSwitchTo(oldContext); return result; } /* * MJCompare * * Compare the mergejoinable values of the current two input tuples * and return 0 if they are equal (ie, the mergejoin equalities all * succeed), >0 if outer > inner, <0 if outer < inner. * * MJEvalOuterValues and MJEvalInnerValues must already have been called * for the current outer and inner tuples, respectively. */ static int MJCompare(MergeJoinState *mergestate) { int result = 0; bool nulleqnull = false; ExprContext *econtext = mergestate->js.ps.ps_ExprContext; int i; MemoryContext oldContext; /* * Call the comparison functions in short-lived context, in case they leak * memory. */ ResetExprContext(econtext); oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory); for (i = 0; i < mergestate->mj_NumClauses; i++) { MergeJoinClause clause = &mergestate->mj_Clauses[i]; /* * Special case for NULL-vs-NULL, else use standard comparison. */ if (clause->lisnull && clause->risnull) { nulleqnull = true; /* NULL "=" NULL */ continue; } result = ApplySortComparator(clause->ldatum, clause->lisnull, clause->rdatum, clause->risnull, &clause->ssup); if (result != 0) break; } /* * If we had any NULL-vs-NULL inputs, we do not want to report that the * tuples are equal. Instead, if result is still 0, change it to +1. This * will result in advancing the inner side of the join. * * Likewise, if there was a constant-false joinqual, do not report * equality. We have to check this as part of the mergequals, else the * rescan logic will do the wrong thing. */ if (result == 0 && (nulleqnull || mergestate->mj_ConstFalseJoin)) result = 1; MemoryContextSwitchTo(oldContext); return result; } /* * Generate a fake join tuple with nulls for the inner tuple, * and return it if it passes the non-join quals. */ static TupleTableSlot * MJFillOuter(MergeJoinState *node) { ExprContext *econtext = node->js.ps.ps_ExprContext; ExprState *otherqual = node->js.ps.qual; ResetExprContext(econtext); econtext->ecxt_outertuple = node->mj_OuterTupleSlot; econtext->ecxt_innertuple = node->mj_NullInnerTupleSlot; if (ExecQual(otherqual, econtext)) { /* * qualification succeeded. now form the desired projection tuple and * return the slot containing it. */ MJ_printf("ExecMergeJoin: returning outer fill tuple\n"); return ExecProject(node->js.ps.ps_ProjInfo); } else InstrCountFiltered2(node, 1); return NULL; } /* * Generate a fake join tuple with nulls for the outer tuple, * and return it if it passes the non-join quals. */ static TupleTableSlot * MJFillInner(MergeJoinState *node) { ExprContext *econtext = node->js.ps.ps_ExprContext; ExprState *otherqual = node->js.ps.qual; ResetExprContext(econtext); econtext->ecxt_outertuple = node->mj_NullOuterTupleSlot; econtext->ecxt_innertuple = node->mj_InnerTupleSlot; if (ExecQual(otherqual, econtext)) { /* * qualification succeeded. now form the desired projection tuple and * return the slot containing it. */ MJ_printf("ExecMergeJoin: returning inner fill tuple\n"); return ExecProject(node->js.ps.ps_ProjInfo); } else InstrCountFiltered2(node, 1); return NULL; } /* * Check that a qual condition is constant true or constant false. * If it is constant false (or null), set *is_const_false to true. * * Constant true would normally be represented by a NIL list, but we allow an * actual bool Const as well. We do expect that the planner will have thrown * away any non-constant terms that have been ANDed with a constant false. */ static bool check_constant_qual(List *qual, bool *is_const_false) { ListCell *lc; foreach(lc, qual) { Const *con = (Const *) lfirst(lc); if (!con || !IsA(con, Const)) return false; if (con->constisnull || !DatumGetBool(con->constvalue)) *is_const_false = true; } return true; } /* ---------------------------------------------------------------- * ExecMergeTupleDump * * This function is called through the MJ_dump() macro * when EXEC_MERGEJOINDEBUG is defined * ---------------------------------------------------------------- */ #ifdef EXEC_MERGEJOINDEBUG static void ExecMergeTupleDumpOuter(MergeJoinState *mergestate) { TupleTableSlot *outerSlot = mergestate->mj_OuterTupleSlot; printf("==== outer tuple ====\n"); if (TupIsNull(outerSlot)) printf("(nil)\n"); else MJ_debugtup(outerSlot); } static void ExecMergeTupleDumpInner(MergeJoinState *mergestate) { TupleTableSlot *innerSlot = mergestate->mj_InnerTupleSlot; printf("==== inner tuple ====\n"); if (TupIsNull(innerSlot)) printf("(nil)\n"); else MJ_debugtup(innerSlot); } static void ExecMergeTupleDumpMarked(MergeJoinState *mergestate) { TupleTableSlot *markedSlot = mergestate->mj_MarkedTupleSlot; printf("==== marked tuple ====\n"); if (TupIsNull(markedSlot)) printf("(nil)\n"); else MJ_debugtup(markedSlot); } static void ExecMergeTupleDump(MergeJoinState *mergestate) { printf("******** ExecMergeTupleDump ********\n"); ExecMergeTupleDumpOuter(mergestate); ExecMergeTupleDumpInner(mergestate); ExecMergeTupleDumpMarked(mergestate); printf("********\n"); } #endif /* ---------------------------------------------------------------- * ExecMergeJoin * ---------------------------------------------------------------- */ static TupleTableSlot * ExecMergeJoin(PlanState *pstate) { MergeJoinState *node = castNode(MergeJoinState, pstate); ExprState *joinqual; ExprState *otherqual; bool qualResult; int compareResult; PlanState *innerPlan; TupleTableSlot *innerTupleSlot; PlanState *outerPlan; TupleTableSlot *outerTupleSlot; ExprContext *econtext; bool doFillOuter; bool doFillInner; CHECK_FOR_INTERRUPTS(); /* * get information from node */ innerPlan = innerPlanState(node); outerPlan = outerPlanState(node); econtext = node->js.ps.ps_ExprContext; joinqual = node->js.joinqual; otherqual = node->js.ps.qual; doFillOuter = node->mj_FillOuter; doFillInner = node->mj_FillInner; /* * Reset per-tuple memory context to free any expression evaluation * storage allocated in the previous tuple cycle. */ ResetExprContext(econtext); /* * ok, everything is setup.. let's go to work */ for (;;) { MJ_dump(node); /* * get the current state of the join and do things accordingly. */ switch (node->mj_JoinState) { /* * EXEC_MJ_INITIALIZE_OUTER means that this is the first time * ExecMergeJoin() has been called and so we have to fetch the * first matchable tuple for both outer and inner subplans. We * do the outer side in INITIALIZE_OUTER state, then advance * to INITIALIZE_INNER state for the inner subplan. */ case EXEC_MJ_INITIALIZE_OUTER: MJ_printf("ExecMergeJoin: EXEC_MJ_INITIALIZE_OUTER\n"); outerTupleSlot = ExecProcNode(outerPlan); node->mj_OuterTupleSlot = outerTupleSlot; /* Compute join values and check for unmatchability */ switch (MJEvalOuterValues(node)) { case MJEVAL_MATCHABLE: /* OK to go get the first inner tuple */ node->mj_JoinState = EXEC_MJ_INITIALIZE_INNER; break; case MJEVAL_NONMATCHABLE: /* Stay in same state to fetch next outer tuple */ if (doFillOuter) { /* * Generate a fake join tuple with nulls for the * inner tuple, and return it if it passes the * non-join quals. */ TupleTableSlot *result; result = MJFillOuter(node); if (result) return result; } break; case MJEVAL_ENDOFJOIN: /* No more outer tuples */ MJ_printf("ExecMergeJoin: nothing in outer subplan\n"); if (doFillInner) { /* * Need to emit right-join tuples for remaining * inner tuples. We set MatchedInner = true to * force the ENDOUTER state to advance inner. */ node->mj_JoinState = EXEC_MJ_ENDOUTER; node->mj_MatchedInner = true; break; } /* Otherwise we're done. */ return NULL; } break; case EXEC_MJ_INITIALIZE_INNER: MJ_printf("ExecMergeJoin: EXEC_MJ_INITIALIZE_INNER\n"); innerTupleSlot = ExecProcNode(innerPlan); node->mj_InnerTupleSlot = innerTupleSlot; /* Compute join values and check for unmatchability */ switch (MJEvalInnerValues(node, innerTupleSlot)) { case MJEVAL_MATCHABLE: /* * OK, we have the initial tuples. Begin by skipping * non-matching tuples. */ node->mj_JoinState = EXEC_MJ_SKIP_TEST; break; case MJEVAL_NONMATCHABLE: /* Mark before advancing, if wanted */ if (node->mj_ExtraMarks) ExecMarkPos(innerPlan); /* Stay in same state to fetch next inner tuple */ if (doFillInner) { /* * Generate a fake join tuple with nulls for the * outer tuple, and return it if it passes the * non-join quals. */ TupleTableSlot *result; result = MJFillInner(node); if (result) return result; } break; case MJEVAL_ENDOFJOIN: /* No more inner tuples */ MJ_printf("ExecMergeJoin: nothing in inner subplan\n"); if (doFillOuter) { /* * Need to emit left-join tuples for all outer * tuples, including the one we just fetched. We * set MatchedOuter = false to force the ENDINNER * state to emit first tuple before advancing * outer. */ node->mj_JoinState = EXEC_MJ_ENDINNER; node->mj_MatchedOuter = false; break; } /* Otherwise we're done. */ return NULL; } break; /* * EXEC_MJ_JOINTUPLES means we have two tuples which satisfied * the merge clause so we join them and then proceed to get * the next inner tuple (EXEC_MJ_NEXTINNER). */ case EXEC_MJ_JOINTUPLES: MJ_printf("ExecMergeJoin: EXEC_MJ_JOINTUPLES\n"); /* * Set the next state machine state. The right things will * happen whether we return this join tuple or just fall * through to continue the state machine execution. */ node->mj_JoinState = EXEC_MJ_NEXTINNER; /* * Check the extra qual conditions to see if we actually want * to return this join tuple. If not, can proceed with merge. * We must distinguish the additional joinquals (which must * pass to consider the tuples "matched" for outer-join logic) * from the otherquals (which must pass before we actually * return the tuple). * * We don't bother with a ResetExprContext here, on the * assumption that we just did one while checking the merge * qual. One per tuple should be sufficient. We do have to * set up the econtext links to the tuples for ExecQual to * use. */ outerTupleSlot = node->mj_OuterTupleSlot; econtext->ecxt_outertuple = outerTupleSlot; innerTupleSlot = node->mj_InnerTupleSlot; econtext->ecxt_innertuple = innerTupleSlot; qualResult = (joinqual == NULL || ExecQual(joinqual, econtext)); MJ_DEBUG_QUAL(joinqual, qualResult); if (qualResult) { node->mj_MatchedOuter = true; node->mj_MatchedInner = true; /* In an antijoin, we never return a matched tuple */ if (node->js.jointype == JOIN_ANTI) { node->mj_JoinState = EXEC_MJ_NEXTOUTER; break; } /* * If we only need to join to the first matching inner * tuple, then consider returning this one, but after that * continue with next outer tuple. */ if (node->js.single_match) node->mj_JoinState = EXEC_MJ_NEXTOUTER; qualResult = (otherqual == NULL || ExecQual(otherqual, econtext)); MJ_DEBUG_QUAL(otherqual, qualResult); if (qualResult) { /* * qualification succeeded. now form the desired * projection tuple and return the slot containing it. */ MJ_printf("ExecMergeJoin: returning tuple\n"); return ExecProject(node->js.ps.ps_ProjInfo); } else InstrCountFiltered2(node, 1); } else InstrCountFiltered1(node, 1); break; /* * EXEC_MJ_NEXTINNER means advance the inner scan to the next * tuple. If the tuple is not nil, we then proceed to test it * against the join qualification. * * Before advancing, we check to see if we must emit an * outer-join fill tuple for this inner tuple. */ case EXEC_MJ_NEXTINNER: MJ_printf("ExecMergeJoin: EXEC_MJ_NEXTINNER\n"); if (doFillInner && !node->mj_MatchedInner) { /* * Generate a fake join tuple with nulls for the outer * tuple, and return it if it passes the non-join quals. */ TupleTableSlot *result; node->mj_MatchedInner = true; /* do it only once */ result = MJFillInner(node); if (result) return result; } /* * now we get the next inner tuple, if any. If there's none, * advance to next outer tuple (which may be able to join to * previously marked tuples). * * NB: must NOT do "extraMarks" here, since we may need to * return to previously marked tuples. */ innerTupleSlot = ExecProcNode(innerPlan); node->mj_InnerTupleSlot = innerTupleSlot; MJ_DEBUG_PROC_NODE(innerTupleSlot); node->mj_MatchedInner = false; /* Compute join values and check for unmatchability */ switch (MJEvalInnerValues(node, innerTupleSlot)) { case MJEVAL_MATCHABLE: /* * Test the new inner tuple to see if it matches * outer. * * If they do match, then we join them and move on to * the next inner tuple (EXEC_MJ_JOINTUPLES). * * If they do not match then advance to next outer * tuple. */ compareResult = MJCompare(node); MJ_DEBUG_COMPARE(compareResult); if (compareResult == 0) node->mj_JoinState = EXEC_MJ_JOINTUPLES; else { Assert(compareResult < 0); node->mj_JoinState = EXEC_MJ_NEXTOUTER; } break; case MJEVAL_NONMATCHABLE: /* * It contains a NULL and hence can't match any outer * tuple, so we can skip the comparison and assume the * new tuple is greater than current outer. */ node->mj_JoinState = EXEC_MJ_NEXTOUTER; break; case MJEVAL_ENDOFJOIN: /* * No more inner tuples. However, this might be only * effective and not physical end of inner plan, so * force mj_InnerTupleSlot to null to make sure we * don't fetch more inner tuples. (We need this hack * because we are not transiting to a state where the * inner plan is assumed to be exhausted.) */ node->mj_InnerTupleSlot = NULL; node->mj_JoinState = EXEC_MJ_NEXTOUTER; break; } break; /*------------------------------------------- * EXEC_MJ_NEXTOUTER means * * outer inner * outer tuple - 5 5 - marked tuple * 5 5 * 6 6 - inner tuple * 7 7 * * we know we just bumped into the * first inner tuple > current outer tuple (or possibly * the end of the inner stream) * so get a new outer tuple and then * proceed to test it against the marked tuple * (EXEC_MJ_TESTOUTER) * * Before advancing, we check to see if we must emit an * outer-join fill tuple for this outer tuple. *------------------------------------------------ */ case EXEC_MJ_NEXTOUTER: MJ_printf("ExecMergeJoin: EXEC_MJ_NEXTOUTER\n"); if (doFillOuter && !node->mj_MatchedOuter) { /* * Generate a fake join tuple with nulls for the inner * tuple, and return it if it passes the non-join quals. */ TupleTableSlot *result; node->mj_MatchedOuter = true; /* do it only once */ result = MJFillOuter(node); if (result) return result; } /* * now we get the next outer tuple, if any */ outerTupleSlot = ExecProcNode(outerPlan); node->mj_OuterTupleSlot = outerTupleSlot; MJ_DEBUG_PROC_NODE(outerTupleSlot); node->mj_MatchedOuter = false; /* Compute join values and check for unmatchability */ switch (MJEvalOuterValues(node)) { case MJEVAL_MATCHABLE: /* Go test the new tuple against the marked tuple */ node->mj_JoinState = EXEC_MJ_TESTOUTER; break; case MJEVAL_NONMATCHABLE: /* Can't match, so fetch next outer tuple */ node->mj_JoinState = EXEC_MJ_NEXTOUTER; break; case MJEVAL_ENDOFJOIN: /* No more outer tuples */ MJ_printf("ExecMergeJoin: end of outer subplan\n"); innerTupleSlot = node->mj_InnerTupleSlot; if (doFillInner && !TupIsNull(innerTupleSlot)) { /* * Need to emit right-join tuples for remaining * inner tuples. */ node->mj_JoinState = EXEC_MJ_ENDOUTER; break; } /* Otherwise we're done. */ return NULL; } break; /*-------------------------------------------------------- * EXEC_MJ_TESTOUTER If the new outer tuple and the marked * tuple satisfy the merge clause then we know we have * duplicates in the outer scan so we have to restore the * inner scan to the marked tuple and proceed to join the * new outer tuple with the inner tuples. * * This is the case when * outer inner * 4 5 - marked tuple * outer tuple - 5 5 * new outer tuple - 5 5 * 6 8 - inner tuple * 7 12 * * new outer tuple == marked tuple * * If the outer tuple fails the test, then we are done * with the marked tuples, and we have to look for a * match to the current inner tuple. So we will * proceed to skip outer tuples until outer >= inner * (EXEC_MJ_SKIP_TEST). * * This is the case when * * outer inner * 5 5 - marked tuple * outer tuple - 5 5 * new outer tuple - 6 8 - inner tuple * 7 12 * * new outer tuple > marked tuple * *--------------------------------------------------------- */ case EXEC_MJ_TESTOUTER: MJ_printf("ExecMergeJoin: EXEC_MJ_TESTOUTER\n"); /* * Here we must compare the outer tuple with the marked inner * tuple. (We can ignore the result of MJEvalInnerValues, * since the marked inner tuple is certainly matchable.) */ innerTupleSlot = node->mj_MarkedTupleSlot; (void) MJEvalInnerValues(node, innerTupleSlot); compareResult = MJCompare(node); MJ_DEBUG_COMPARE(compareResult); if (compareResult == 0) { /* * the merge clause matched so now we restore the inner * scan position to the first mark, and go join that tuple * (and any following ones) to the new outer. * * If we were able to determine mark and restore are not * needed, then we don't have to back up; the current * inner is already the first possible match. * * NOTE: we do not need to worry about the MatchedInner * state for the rescanned inner tuples. We know all of * them will match this new outer tuple and therefore * won't be emitted as fill tuples. This works *only* * because we require the extra joinquals to be constant * when doing a right or full join --- otherwise some of * the rescanned tuples might fail the extra joinquals. * This obviously won't happen for a constant-true extra * joinqual, while the constant-false case is handled by * forcing the merge clause to never match, so we never * get here. */ if (!node->mj_SkipMarkRestore) { ExecRestrPos(innerPlan); /* * ExecRestrPos probably should give us back a new * Slot, but since it doesn't, use the marked slot. * (The previously returned mj_InnerTupleSlot cannot * be assumed to hold the required tuple.) */ node->mj_InnerTupleSlot = innerTupleSlot; /* we need not do MJEvalInnerValues again */ } node->mj_JoinState = EXEC_MJ_JOINTUPLES; } else { /* ---------------- * if the new outer tuple didn't match the marked inner * tuple then we have a case like: * * outer inner * 4 4 - marked tuple * new outer - 5 4 * 6 5 - inner tuple * 7 * * which means that all subsequent outer tuples will be * larger than our marked inner tuples. So we need not * revisit any of the marked tuples but can proceed to * look for a match to the current inner. If there's * no more inners, no more matches are possible. * ---------------- */ Assert(compareResult > 0); innerTupleSlot = node->mj_InnerTupleSlot; /* reload comparison data for current inner */ switch (MJEvalInnerValues(node, innerTupleSlot)) { case MJEVAL_MATCHABLE: /* proceed to compare it to the current outer */ node->mj_JoinState = EXEC_MJ_SKIP_TEST; break; case MJEVAL_NONMATCHABLE: /* * current inner can't possibly match any outer; * better to advance the inner scan than the * outer. */ node->mj_JoinState = EXEC_MJ_SKIPINNER_ADVANCE; break; case MJEVAL_ENDOFJOIN: /* No more inner tuples */ if (doFillOuter) { /* * Need to emit left-join tuples for remaining * outer tuples. */ node->mj_JoinState = EXEC_MJ_ENDINNER; break; } /* Otherwise we're done. */ return NULL; } } break; /*---------------------------------------------------------- * EXEC_MJ_SKIP means compare tuples and if they do not * match, skip whichever is lesser. * * For example: * * outer inner * 5 5 * 5 5 * outer tuple - 6 8 - inner tuple * 7 12 * 8 14 * * we have to advance the outer scan * until we find the outer 8. * * On the other hand: * * outer inner * 5 5 * 5 5 * outer tuple - 12 8 - inner tuple * 14 10 * 17 12 * * we have to advance the inner scan * until we find the inner 12. *---------------------------------------------------------- */ case EXEC_MJ_SKIP_TEST: MJ_printf("ExecMergeJoin: EXEC_MJ_SKIP_TEST\n"); /* * before we advance, make sure the current tuples do not * satisfy the mergeclauses. If they do, then we update the * marked tuple position and go join them. */ compareResult = MJCompare(node); MJ_DEBUG_COMPARE(compareResult); if (compareResult == 0) { if (!node->mj_SkipMarkRestore) ExecMarkPos(innerPlan); MarkInnerTuple(node->mj_InnerTupleSlot, node); node->mj_JoinState = EXEC_MJ_JOINTUPLES; } else if (compareResult < 0) node->mj_JoinState = EXEC_MJ_SKIPOUTER_ADVANCE; else /* compareResult > 0 */ node->mj_JoinState = EXEC_MJ_SKIPINNER_ADVANCE; break; /* * SKIPOUTER_ADVANCE: advance over an outer tuple that is * known not to join to any inner tuple. * * Before advancing, we check to see if we must emit an * outer-join fill tuple for this outer tuple. */ case EXEC_MJ_SKIPOUTER_ADVANCE: MJ_printf("ExecMergeJoin: EXEC_MJ_SKIPOUTER_ADVANCE\n"); if (doFillOuter && !node->mj_MatchedOuter) { /* * Generate a fake join tuple with nulls for the inner * tuple, and return it if it passes the non-join quals. */ TupleTableSlot *result; node->mj_MatchedOuter = true; /* do it only once */ result = MJFillOuter(node); if (result) return result; } /* * now we get the next outer tuple, if any */ outerTupleSlot = ExecProcNode(outerPlan); node->mj_OuterTupleSlot = outerTupleSlot; MJ_DEBUG_PROC_NODE(outerTupleSlot); node->mj_MatchedOuter = false; /* Compute join values and check for unmatchability */ switch (MJEvalOuterValues(node)) { case MJEVAL_MATCHABLE: /* Go test the new tuple against the current inner */ node->mj_JoinState = EXEC_MJ_SKIP_TEST; break; case MJEVAL_NONMATCHABLE: /* Can't match, so fetch next outer tuple */ node->mj_JoinState = EXEC_MJ_SKIPOUTER_ADVANCE; break; case MJEVAL_ENDOFJOIN: /* No more outer tuples */ MJ_printf("ExecMergeJoin: end of outer subplan\n"); innerTupleSlot = node->mj_InnerTupleSlot; if (doFillInner && !TupIsNull(innerTupleSlot)) { /* * Need to emit right-join tuples for remaining * inner tuples. */ node->mj_JoinState = EXEC_MJ_ENDOUTER; break; } /* Otherwise we're done. */ return NULL; } break; /* * SKIPINNER_ADVANCE: advance over an inner tuple that is * known not to join to any outer tuple. * * Before advancing, we check to see if we must emit an * outer-join fill tuple for this inner tuple. */ case EXEC_MJ_SKIPINNER_ADVANCE: MJ_printf("ExecMergeJoin: EXEC_MJ_SKIPINNER_ADVANCE\n"); if (doFillInner && !node->mj_MatchedInner) { /* * Generate a fake join tuple with nulls for the outer * tuple, and return it if it passes the non-join quals. */ TupleTableSlot *result; node->mj_MatchedInner = true; /* do it only once */ result = MJFillInner(node); if (result) return result; } /* Mark before advancing, if wanted */ if (node->mj_ExtraMarks) ExecMarkPos(innerPlan); /* * now we get the next inner tuple, if any */ innerTupleSlot = ExecProcNode(innerPlan); node->mj_InnerTupleSlot = innerTupleSlot; MJ_DEBUG_PROC_NODE(innerTupleSlot); node->mj_MatchedInner = false; /* Compute join values and check for unmatchability */ switch (MJEvalInnerValues(node, innerTupleSlot)) { case MJEVAL_MATCHABLE: /* proceed to compare it to the current outer */ node->mj_JoinState = EXEC_MJ_SKIP_TEST; break; case MJEVAL_NONMATCHABLE: /* * current inner can't possibly match any outer; * better to advance the inner scan than the outer. */ node->mj_JoinState = EXEC_MJ_SKIPINNER_ADVANCE; break; case MJEVAL_ENDOFJOIN: /* No more inner tuples */ MJ_printf("ExecMergeJoin: end of inner subplan\n"); outerTupleSlot = node->mj_OuterTupleSlot; if (doFillOuter && !TupIsNull(outerTupleSlot)) { /* * Need to emit left-join tuples for remaining * outer tuples. */ node->mj_JoinState = EXEC_MJ_ENDINNER; break; } /* Otherwise we're done. */ return NULL; } break; /* * EXEC_MJ_ENDOUTER means we have run out of outer tuples, but * are doing a right/full join and therefore must null-fill * any remaining unmatched inner tuples. */ case EXEC_MJ_ENDOUTER: MJ_printf("ExecMergeJoin: EXEC_MJ_ENDOUTER\n"); Assert(doFillInner); if (!node->mj_MatchedInner) { /* * Generate a fake join tuple with nulls for the outer * tuple, and return it if it passes the non-join quals. */ TupleTableSlot *result; node->mj_MatchedInner = true; /* do it only once */ result = MJFillInner(node); if (result) return result; } /* Mark before advancing, if wanted */ if (node->mj_ExtraMarks) ExecMarkPos(innerPlan); /* * now we get the next inner tuple, if any */ innerTupleSlot = ExecProcNode(innerPlan); node->mj_InnerTupleSlot = innerTupleSlot; MJ_DEBUG_PROC_NODE(innerTupleSlot); node->mj_MatchedInner = false; if (TupIsNull(innerTupleSlot)) { MJ_printf("ExecMergeJoin: end of inner subplan\n"); return NULL; } /* Else remain in ENDOUTER state and process next tuple. */ break; /* * EXEC_MJ_ENDINNER means we have run out of inner tuples, but * are doing a left/full join and therefore must null- fill * any remaining unmatched outer tuples. */ case EXEC_MJ_ENDINNER: MJ_printf("ExecMergeJoin: EXEC_MJ_ENDINNER\n"); Assert(doFillOuter); if (!node->mj_MatchedOuter) { /* * Generate a fake join tuple with nulls for the inner * tuple, and return it if it passes the non-join quals. */ TupleTableSlot *result; node->mj_MatchedOuter = true; /* do it only once */ result = MJFillOuter(node); if (result) return result; } /* * now we get the next outer tuple, if any */ outerTupleSlot = ExecProcNode(outerPlan); node->mj_OuterTupleSlot = outerTupleSlot; MJ_DEBUG_PROC_NODE(outerTupleSlot); node->mj_MatchedOuter = false; if (TupIsNull(outerTupleSlot)) { MJ_printf("ExecMergeJoin: end of outer subplan\n"); return NULL; } /* Else remain in ENDINNER state and process next tuple. */ break; /* * broken state value? */ default: elog(ERROR, "unrecognized mergejoin state: %d", (int) node->mj_JoinState); } } } /* ---------------------------------------------------------------- * ExecInitMergeJoin * ---------------------------------------------------------------- */ MergeJoinState * ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags) { MergeJoinState *mergestate; TupleDesc outerDesc, innerDesc; const TupleTableSlotOps *innerOps; /* check for unsupported flags */ Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK))); MJ1_printf("ExecInitMergeJoin: %s\n", "initializing node"); /* * create state structure */ mergestate = makeNode(MergeJoinState); mergestate->js.ps.plan = (Plan *) node; mergestate->js.ps.state = estate; mergestate->js.ps.ExecProcNode = ExecMergeJoin; mergestate->js.jointype = node->join.jointype; mergestate->mj_ConstFalseJoin = false; /* * Miscellaneous initialization * * create expression context for node */ ExecAssignExprContext(estate, &mergestate->js.ps); /* * we need two additional econtexts in which we can compute the join * expressions from the left and right input tuples. The node's regular * econtext won't do because it gets reset too often. */ mergestate->mj_OuterEContext = CreateExprContext(estate); mergestate->mj_InnerEContext = CreateExprContext(estate); /* * initialize child nodes * * inner child must support MARK/RESTORE, unless we have detected that we * don't need that. Note that skip_mark_restore must never be set if * there are non-mergeclause joinquals, since the logic wouldn't work. */ Assert(node->join.joinqual == NIL || !node->skip_mark_restore); mergestate->mj_SkipMarkRestore = node->skip_mark_restore; outerPlanState(mergestate) = ExecInitNode(outerPlan(node), estate, eflags); outerDesc = ExecGetResultType(outerPlanState(mergestate)); innerPlanState(mergestate) = ExecInitNode(innerPlan(node), estate, mergestate->mj_SkipMarkRestore ? eflags : (eflags | EXEC_FLAG_MARK)); innerDesc = ExecGetResultType(innerPlanState(mergestate)); /* * For certain types of inner child nodes, it is advantageous to issue * MARK every time we advance past an inner tuple we will never return to. * For other types, MARK on a tuple we cannot return to is a waste of * cycles. Detect which case applies and set mj_ExtraMarks if we want to * issue "unnecessary" MARK calls. * * Currently, only Material wants the extra MARKs, and it will be helpful * only if eflags doesn't specify REWIND. * * Note that for IndexScan and IndexOnlyScan, it is *necessary* that we * not set mj_ExtraMarks; otherwise we might attempt to set a mark before * the first inner tuple, which they do not support. */ if (IsA(innerPlan(node), Material) && (eflags & EXEC_FLAG_REWIND) == 0 && !mergestate->mj_SkipMarkRestore) mergestate->mj_ExtraMarks = true; else mergestate->mj_ExtraMarks = false; /* * Initialize result slot, type and projection. */ ExecInitResultTupleSlotTL(&mergestate->js.ps, &TTSOpsVirtual); ExecAssignProjectionInfo(&mergestate->js.ps, NULL); /* * tuple table initialization */ innerOps = ExecGetResultSlotOps(innerPlanState(mergestate), NULL); mergestate->mj_MarkedTupleSlot = ExecInitExtraTupleSlot(estate, innerDesc, innerOps); /* * initialize child expressions */ mergestate->js.ps.qual = ExecInitQual(node->join.plan.qual, (PlanState *) mergestate); mergestate->js.joinqual = ExecInitQual(node->join.joinqual, (PlanState *) mergestate); /* mergeclauses are handled below */ /* * detect whether we need only consider the first matching inner tuple */ mergestate->js.single_match = (node->join.inner_unique || node->join.jointype == JOIN_SEMI); /* set up null tuples for outer joins, if needed */ switch (node->join.jointype) { case JOIN_INNER: case JOIN_SEMI: mergestate->mj_FillOuter = false; mergestate->mj_FillInner = false; break; case JOIN_LEFT: case JOIN_ANTI: mergestate->mj_FillOuter = true; mergestate->mj_FillInner = false; mergestate->mj_NullInnerTupleSlot = ExecInitNullTupleSlot(estate, innerDesc, &TTSOpsVirtual); break; case JOIN_RIGHT: mergestate->mj_FillOuter = false; mergestate->mj_FillInner = true; mergestate->mj_NullOuterTupleSlot = ExecInitNullTupleSlot(estate, outerDesc, &TTSOpsVirtual); /* * Can't handle right or full join with non-constant extra * joinclauses. This should have been caught by planner. */ if (!check_constant_qual(node->join.joinqual, &mergestate->mj_ConstFalseJoin)) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("RIGHT JOIN is only supported with merge-joinable join conditions"))); break; case JOIN_FULL: mergestate->mj_FillOuter = true; mergestate->mj_FillInner = true; mergestate->mj_NullOuterTupleSlot = ExecInitNullTupleSlot(estate, outerDesc, &TTSOpsVirtual); mergestate->mj_NullInnerTupleSlot = ExecInitNullTupleSlot(estate, innerDesc, &TTSOpsVirtual); /* * Can't handle right or full join with non-constant extra * joinclauses. This should have been caught by planner. */ if (!check_constant_qual(node->join.joinqual, &mergestate->mj_ConstFalseJoin)) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("FULL JOIN is only supported with merge-joinable join conditions"))); break; default: elog(ERROR, "unrecognized join type: %d", (int) node->join.jointype); } /* * preprocess the merge clauses */ mergestate->mj_NumClauses = list_length(node->mergeclauses); mergestate->mj_Clauses = MJExamineQuals(node->mergeclauses, node->mergeFamilies, node->mergeCollations, node->mergeStrategies, node->mergeNullsFirst, (PlanState *) mergestate); /* * initialize join state */ mergestate->mj_JoinState = EXEC_MJ_INITIALIZE_OUTER; mergestate->mj_MatchedOuter = false; mergestate->mj_MatchedInner = false; mergestate->mj_OuterTupleSlot = NULL; mergestate->mj_InnerTupleSlot = NULL; /* * initialization successful */ MJ1_printf("ExecInitMergeJoin: %s\n", "node initialized"); return mergestate; } /* ---------------------------------------------------------------- * ExecEndMergeJoin * * old comments * frees storage allocated through C routines. * ---------------------------------------------------------------- */ void ExecEndMergeJoin(MergeJoinState *node) { MJ1_printf("ExecEndMergeJoin: %s\n", "ending node processing"); /* * Free the exprcontext */ ExecFreeExprContext(&node->js.ps); /* * clean out the tuple table */ ExecClearTuple(node->js.ps.ps_ResultTupleSlot); ExecClearTuple(node->mj_MarkedTupleSlot); /* * shut down the subplans */ ExecEndNode(innerPlanState(node)); ExecEndNode(outerPlanState(node)); MJ1_printf("ExecEndMergeJoin: %s\n", "node processing ended"); } void ExecReScanMergeJoin(MergeJoinState *node) { ExecClearTuple(node->mj_MarkedTupleSlot); node->mj_JoinState = EXEC_MJ_INITIALIZE_OUTER; node->mj_MatchedOuter = false; node->mj_MatchedInner = false; node->mj_OuterTupleSlot = NULL; node->mj_InnerTupleSlot = NULL; /* * if chgParam of subnodes is not null then plans will be re-scanned by * first ExecProcNode. */ if (node->js.ps.lefttree->chgParam == NULL) ExecReScan(node->js.ps.lefttree); if (node->js.ps.righttree->chgParam == NULL) ExecReScan(node->js.ps.righttree); }