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Replace EEOP_DONE with special steps for return/no return
author Daniel Gustafsson <dgustafsson@postgresql.org>
2025年3月11日 11:02:38 +0000 (12:02 +0100)
committer Daniel Gustafsson <dgustafsson@postgresql.org>
2025年3月11日 11:02:38 +0000 (12:02 +0100)
Knowing when the side-effects of an expression is the intended result
of the execution, rather than the returnvalue, is important for being
able generate more efficient JITed code. This replaces EEOP_DONE with
two new steps: EEOP_DONE_RETURN and EEOP_DONE_NO_RETURN. Expressions
which return a value should use the former step; expressions used for
their side-effects which don't return value should use the latter.

Author: Andres Freund <andres@anarazel.de>
Co-authored-by: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Andreas Karlsson <andreas@proxel.se>
Discussion: https://postgr.es/m/415721CE-7D2E-4B74-B5D9-1950083BA03E@yesql.se
Discussion: https://postgr.es/m/20191023163849.sosqbfs5yenocez3@alap3.anarazel.de

src/backend/executor/README patch | blob | blame | history
src/backend/executor/execExpr.c patch | blob | blame | history
src/backend/executor/execExprInterp.c patch | blob | blame | history
src/backend/executor/nodeAgg.c patch | blob | blame | history
src/backend/jit/llvm/llvmjit_expr.c patch | blob | blame | history
src/include/executor/execExpr.h patch | blob | blame | history
src/include/executor/executor.h patch | blob | blame | history

diff --git a/src/backend/executor/README b/src/backend/executor/README
index 1db9642be85402c8dad234db75cb56880faf1cfd..02745c23ed974e33e0955a4bb1058ed6f14155e5 100644 (file)
--- a/src/backend/executor/README
+++ b/src/backend/executor/README
@@ -133,9 +133,14 @@ is used by the function evaluation step, thus avoiding extra work to copy
the result values around.
The last entry in a completed ExprState->steps array is always an
-EEOP_DONE step; this removes the need to test for end-of-array while
-iterating. Also, if the expression contains any variable references (to
-user columns of the ExprContext's INNER, OUTER, or SCAN tuples), the steps
+EEOP_DONE_RETURN or EEOP_DONE_NO_RETURN step; this removes the need to
+test for end-of-array while iterating. The former is used when the
+expression returns a value directly, the latter when side-effects of
+expression initialization are the goal (e.g. for projection or
+aggregate transition value computation).
+
+Also, if the expression contains any variable references (to user
+columns of the ExprContext's INNER, OUTER, or SCAN tuples), the steps
array begins with EEOP_*_FETCHSOME steps that ensure that the relevant
tuples have been deconstructed to make the required columns directly
available (cf. slot_getsomeattrs()). This allows individual Var-fetching
diff --git a/src/backend/executor/execExpr.c b/src/backend/executor/execExpr.c
index 03566c4d18166f7379eef32a593fd2bee255c8a9..0175b152980194c7db498d276d4635135a964d9d 100644 (file)
--- a/src/backend/executor/execExpr.c
+++ b/src/backend/executor/execExpr.c
@@ -8,7 +8,7 @@
* using ExecInitExpr() et al. This converts the tree into a flat array
* of ExprEvalSteps, which may be thought of as instructions in a program.
* At runtime, we'll execute steps, starting with the first, until we reach
- * an EEOP_DONE opcode.
+ * an EEOP_DONE_{RETURN|NO_RETURN} opcode.
*
* This file contains the "compilation" logic. It is independent of the
* specific execution technology we use (switch statement, computed goto,
@@ -162,7 +162,7 @@ ExecInitExpr(Expr *node, PlanState *parent)
ExecInitExprRec(node, state, &state->resvalue, &state->resnull);
/* Finally, append a DONE step */
- scratch.opcode = EEOP_DONE;
+ scratch.opcode = EEOP_DONE_RETURN;
ExprEvalPushStep(state, &scratch);
ExecReadyExpr(state);
@@ -199,7 +199,7 @@ ExecInitExprWithParams(Expr *node, ParamListInfo ext_params)
ExecInitExprRec(node, state, &state->resvalue, &state->resnull);
/* Finally, append a DONE step */
- scratch.opcode = EEOP_DONE;
+ scratch.opcode = EEOP_DONE_RETURN;
ExprEvalPushStep(state, &scratch);
ExecReadyExpr(state);
@@ -291,7 +291,7 @@ ExecInitQual(List *qual, PlanState *parent)
* have yielded TRUE, and since its result is stored in the desired output
* location, we're done.
*/
- scratch.opcode = EEOP_DONE;
+ scratch.opcode = EEOP_DONE_RETURN;
ExprEvalPushStep(state, &scratch);
ExecReadyExpr(state);
@@ -503,7 +503,7 @@ ExecBuildProjectionInfo(List *targetList,
}
}
- scratch.opcode = EEOP_DONE;
+ scratch.opcode = EEOP_DONE_NO_RETURN;
ExprEvalPushStep(state, &scratch);
ExecReadyExpr(state);
@@ -742,7 +742,7 @@ ExecBuildUpdateProjection(List *targetList,
}
}
- scratch.opcode = EEOP_DONE;
+ scratch.opcode = EEOP_DONE_NO_RETURN;
ExprEvalPushStep(state, &scratch);
ExecReadyExpr(state);
@@ -1714,7 +1714,7 @@ ExecInitExprRec(Expr *node, ExprState *state,
else
{
/* Not trivial, so append a DONE step */
- scratch.opcode = EEOP_DONE;
+ scratch.opcode = EEOP_DONE_RETURN;
ExprEvalPushStep(elemstate, &scratch);
/* and ready the subexpression */
ExecReadyExpr(elemstate);
@@ -3991,7 +3991,7 @@ ExecBuildAggTrans(AggState *aggstate, AggStatePerPhase phase,
scratch.resvalue = NULL;
scratch.resnull = NULL;
- scratch.opcode = EEOP_DONE;
+ scratch.opcode = EEOP_DONE_NO_RETURN;
ExprEvalPushStep(state, &scratch);
ExecReadyExpr(state);
@@ -4258,7 +4258,7 @@ ExecBuildHash32FromAttrs(TupleDesc desc, const TupleTableSlotOps *ops,
scratch.resvalue = NULL;
scratch.resnull = NULL;
- scratch.opcode = EEOP_DONE;
+ scratch.opcode = EEOP_DONE_RETURN;
ExprEvalPushStep(state, &scratch);
ExecReadyExpr(state);
@@ -4431,7 +4431,7 @@ ExecBuildHash32Expr(TupleDesc desc, const TupleTableSlotOps *ops,
scratch.resvalue = NULL;
scratch.resnull = NULL;
- scratch.opcode = EEOP_DONE;
+ scratch.opcode = EEOP_DONE_RETURN;
ExprEvalPushStep(state, &scratch);
ExecReadyExpr(state);
@@ -4586,7 +4586,7 @@ ExecBuildGroupingEqual(TupleDesc ldesc, TupleDesc rdesc,
scratch.resvalue = NULL;
scratch.resnull = NULL;
- scratch.opcode = EEOP_DONE;
+ scratch.opcode = EEOP_DONE_RETURN;
ExprEvalPushStep(state, &scratch);
ExecReadyExpr(state);
@@ -4722,7 +4722,7 @@ ExecBuildParamSetEqual(TupleDesc desc,
scratch.resvalue = NULL;
scratch.resnull = NULL;
- scratch.opcode = EEOP_DONE;
+ scratch.opcode = EEOP_DONE_RETURN;
ExprEvalPushStep(state, &scratch);
ExecReadyExpr(state);
diff --git a/src/backend/executor/execExprInterp.c b/src/backend/executor/execExprInterp.c
index 1c3477b03c9397f4422926522f50492cb08df063..491ecad8dc664c8e12f8269a51432a4cb4bbbcc6 100644 (file)
--- a/src/backend/executor/execExprInterp.c
+++ b/src/backend/executor/execExprInterp.c
@@ -246,7 +246,8 @@ ExecReadyInterpretedExpr(ExprState *state)
/* Simple validity checks on expression */
Assert(state->steps_len >= 1);
- Assert(state->steps[state->steps_len - 1].opcode == EEOP_DONE);
+ Assert(state->steps[state->steps_len - 1].opcode == EEOP_DONE_RETURN ||
+ state->steps[state->steps_len - 1].opcode == EEOP_DONE_NO_RETURN);
/*
* Don't perform redundant initialization. This is unreachable in current
@@ -469,7 +470,8 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
*/
#if defined(EEO_USE_COMPUTED_GOTO)
static const void *const dispatch_table[] = {
- &&CASE_EEOP_DONE,
+ &&CASE_EEOP_DONE_RETURN,
+ &&CASE_EEOP_DONE_NO_RETURN,
&&CASE_EEOP_INNER_FETCHSOME,
&&CASE_EEOP_OUTER_FETCHSOME,
&&CASE_EEOP_SCAN_FETCHSOME,
@@ -612,9 +614,16 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
EEO_SWITCH()
{
- EEO_CASE(EEOP_DONE)
+ EEO_CASE(EEOP_DONE_RETURN)
{
- goto out;
+ *isnull = state->resnull;
+ return state->resvalue;
+ }
+
+ EEO_CASE(EEOP_DONE_NO_RETURN)
+ {
+ Assert(isnull == NULL);
+ return (Datum) 0;
}
EEO_CASE(EEOP_INNER_FETCHSOME)
@@ -2188,13 +2197,13 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
{
/* unreachable */
Assert(false);
- goto out;
+ goto out_error;
}
}
-out:
- *isnull = state->resnull;
- return state->resvalue;
+out_error:
+ pg_unreachable();
+ return (Datum) 0;
}
/*
diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c
index ceb8c8a8039a706b415c63528689084761ffe301..b4a7698a0b3f7623e7069b0ef6ba97b0a2ff1bf4 100644 (file)
--- a/src/backend/executor/nodeAgg.c
+++ b/src/backend/executor/nodeAgg.c
@@ -816,11 +816,8 @@ advance_transition_function(AggState *aggstate,
static void
advance_aggregates(AggState *aggstate)
{
- bool dummynull;
-
- ExecEvalExprSwitchContext(aggstate->phase->evaltrans,
- aggstate->tmpcontext,
- &dummynull);
+ ExecEvalExprNoReturnSwitchContext(aggstate->phase->evaltrans,
+ aggstate->tmpcontext);
}
/*
diff --git a/src/backend/jit/llvm/llvmjit_expr.c b/src/backend/jit/llvm/llvmjit_expr.c
index f0f5c3bd49f9710c4b0e1639b0e641c3aace43eb..4080b01c17e01cc8558fe1c6500d67a7781c1654 100644 (file)
--- a/src/backend/jit/llvm/llvmjit_expr.c
+++ b/src/backend/jit/llvm/llvmjit_expr.c
@@ -321,7 +321,7 @@ llvm_compile_expr(ExprState *state)
switch (opcode)
{
- case EEOP_DONE:
+ case EEOP_DONE_RETURN:
{
LLVMValueRef v_tmpisnull;
LLVMValueRef v_tmpvalue;
@@ -335,6 +335,10 @@ llvm_compile_expr(ExprState *state)
break;
}
+ case EEOP_DONE_NO_RETURN:
+ LLVMBuildRet(b, l_sizet_const(0));
+ break;
+
case EEOP_INNER_FETCHSOME:
case EEOP_OUTER_FETCHSOME:
case EEOP_SCAN_FETCHSOME:
diff --git a/src/include/executor/execExpr.h b/src/include/executor/execExpr.h
index 191d8fe34dedb0fe53378ebee96d2d373e1c2962..fabdf145a8ee6bb9a1507846b86d391fe7c5827a 100644 (file)
--- a/src/include/executor/execExpr.h
+++ b/src/include/executor/execExpr.h
@@ -65,8 +65,11 @@ typedef struct ExprEvalRowtypeCache
*/
typedef enum ExprEvalOp
{
- /* entire expression has been evaluated completely, return */
- EEOP_DONE,
+ /* entire expression has been evaluated, return value */
+ EEOP_DONE_RETURN,
+
+ /* entire expression has been evaluated, no return value */
+ EEOP_DONE_NO_RETURN,
/* apply slot_getsomeattrs on corresponding tuple slot */
EEOP_INNER_FETCHSOME,
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index d12e3f451d22ba9e0c470c2115a27f08a91f40ce..0d2ffabda684a4a35d93c454da00d809856a18aa 100644 (file)
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -379,6 +379,34 @@ ExecEvalExpr(ExprState *state,
}
#endif
+/*
+ * ExecEvalExprNoReturn
+ *
+ * Like ExecEvalExpr(), but for cases where no return value is expected,
+ * because the side-effects of expression evaluation are what's desired. This
+ * is e.g. used for projection and aggregate transition computation.
+
+ * Evaluate expression identified by "state" in the execution context
+ * given by "econtext".
+ *
+ * The caller should already have switched into the temporary memory context
+ * econtext->ecxt_per_tuple_memory. The convenience entry point
+ * ExecEvalExprNoReturnSwitchContext() is provided for callers who don't
+ * prefer to do the switch in an outer loop.
+ */
+#ifndef FRONTEND
+static inline void
+ExecEvalExprNoReturn(ExprState *state,
+ ExprContext *econtext)
+{
+ PG_USED_FOR_ASSERTS_ONLY Datum retDatum;
+
+ retDatum = state->evalfunc(state, econtext, NULL);
+
+ Assert(retDatum == (Datum) 0);
+}
+#endif
+
/*
* ExecEvalExprSwitchContext
*
@@ -400,6 +428,25 @@ ExecEvalExprSwitchContext(ExprState *state,
}
#endif
+/*
+ * ExecEvalExprNoReturnSwitchContext
+ *
+ * Same as ExecEvalExprNoReturn, but get into the right allocation context
+ * explicitly.
+ */
+#ifndef FRONTEND
+static inline void
+ExecEvalExprNoReturnSwitchContext(ExprState *state,
+ ExprContext *econtext)
+{
+ MemoryContext oldContext;
+
+ oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
+ ExecEvalExprNoReturn(state, econtext);
+ MemoryContextSwitchTo(oldContext);
+}
+#endif
+
/*
* ExecProject
*
@@ -419,7 +466,6 @@ ExecProject(ProjectionInfo *projInfo)
ExprContext *econtext = projInfo->pi_exprContext;
ExprState *state = &projInfo->pi_state;
TupleTableSlot *slot = state->resultslot;
- bool isnull;
/*
* Clear any former contents of the result slot. This makes it safe for
@@ -427,8 +473,8 @@ ExecProject(ProjectionInfo *projInfo)
*/
ExecClearTuple(slot);
- /* Run the expression, discarding scalar result from the last column. */
- (void) ExecEvalExprSwitchContext(state, econtext, &isnull);
+ /* Run the expression */
+ ExecEvalExprNoReturnSwitchContext(state, econtext);
/*
* Successfully formed a result row. Mark the result slot as containing a
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