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Don't generate EEOP_*_FETCHSOME operations for slots know to be virtual.

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That avoids unnecessary work during both interpreted execution, and
JIT compiled expression evaluation. Both benefit from fewer expression
steps needing be processed, and for interpreted execution there now is
a fastpath dedicated to just fetching a value from a virtual
slot. That's e.g. beneficial for hashjoins over nodes that perform
projections, as the hashed columns are currently fetched individually.

Author: Soumyadeep Chakraborty, Andres Freund
Discussion: https://postgr.es/m/CAE-ML+9OKSN71+mHtfMD-L24oDp8dGTfaVjDU6U+j+FNAW5kRQ@mail.gmail.com
pull/47/head
Andres Freund 6 years ago
parent 34c9c53bb0
commit 36d22dd95b
3 changed files with 160 additions and 22 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 43
      src/backend/executor/execExpr.c
  2. 133
      src/backend/executor/execExprInterp.c
  3. 6
      src/backend/jit/llvm/llvmjit_expr.c

43
src/backend/executor/execExpr.c
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@ -65,7 +65,7 @@ static void ExecInitFunc(ExprEvalStep *scratch, Expr *node, List *args,
static void ExecInitExprSlots(ExprState *state, Node *node);
static void ExecPushExprSlots(ExprState *state, LastAttnumInfo *info);
static bool get_last_attnums_walker(Node *node, LastAttnumInfo *info);
static void ExecComputeSlotInfo(ExprState *state, ExprEvalStep *op);
static bool ExecComputeSlotInfo(ExprState *state, ExprEvalStep *op);
static void ExecInitWholeRowVar(ExprEvalStep *scratch, Var *variable,
ExprState *state);
static void ExecInitSubscriptingRef(ExprEvalStep *scratch,
@ -2285,8 +2285,8 @@ ExecPushExprSlots(ExprState *state, LastAttnumInfo *info)
scratch.d.fetch.fixed = false;
scratch.d.fetch.kind = NULL;
scratch.d.fetch.known_desc = NULL;
ExecComputeSlotInfo(state, &scratch);
ExprEvalPushStep(state, &scratch);
if (ExecComputeSlotInfo(state, &scratch))
ExprEvalPushStep(state, &scratch);
}
if (info->last_outer > 0)
{
@ -2295,8 +2295,8 @@ ExecPushExprSlots(ExprState *state, LastAttnumInfo *info)
scratch.d.fetch.fixed = false;
scratch.d.fetch.kind = NULL;
scratch.d.fetch.known_desc = NULL;
ExecComputeSlotInfo(state, &scratch);
ExprEvalPushStep(state, &scratch);
if (ExecComputeSlotInfo(state, &scratch))
ExprEvalPushStep(state, &scratch);
}
if (info->last_scan > 0)
{
@ -2305,8 +2305,8 @@ ExecPushExprSlots(ExprState *state, LastAttnumInfo *info)
scratch.d.fetch.fixed = false;
scratch.d.fetch.kind = NULL;
scratch.d.fetch.known_desc = NULL;
ExecComputeSlotInfo(state, &scratch);
ExprEvalPushStep(state, &scratch);
if (ExecComputeSlotInfo(state, &scratch))
ExprEvalPushStep(state, &scratch);
}
}
@ -2364,14 +2364,21 @@ get_last_attnums_walker(Node *node, LastAttnumInfo *info)
* The goal is to determine whether a slot is 'fixed', that is, every
* evaluation of the expression will have the same type of slot, with an
* equivalent descriptor.
*
* Returns true if the the deforming step is required, false otherwise.
*/
static void
static bool
ExecComputeSlotInfo(ExprState *state, ExprEvalStep *op)
{
PlanState *parent = state->parent;
TupleDesc desc = NULL;
const TupleTableSlotOps *tts_ops = NULL;
bool isfixed = false;
ExprEvalOp opcode = op->opcode;
Assert(opcode == EEOP_INNER_FETCHSOME ||
opcode == EEOP_OUTER_FETCHSOME ||
opcode == EEOP_SCAN_FETCHSOME);
if (op->d.fetch.known_desc != NULL)
{
@ -2383,7 +2390,7 @@ ExecComputeSlotInfo(ExprState *state, ExprEvalStep *op)
{
isfixed = false;
}
else if (op->opcode == EEOP_INNER_FETCHSOME)
else if (opcode == EEOP_INNER_FETCHSOME)
{
PlanState *is = innerPlanState(parent);
@ -2403,7 +2410,7 @@ ExecComputeSlotInfo(ExprState *state, ExprEvalStep *op)
desc = ExecGetResultType(is);
}
}
else if (op->opcode == EEOP_OUTER_FETCHSOME)
else if (opcode == EEOP_OUTER_FETCHSOME)
{
PlanState *os = outerPlanState(parent);
@ -2423,7 +2430,7 @@ ExecComputeSlotInfo(ExprState *state, ExprEvalStep *op)
desc = ExecGetResultType(os);
}
}
else if (op->opcode == EEOP_SCAN_FETCHSOME)
else if (opcode == EEOP_SCAN_FETCHSOME)
{
desc = parent->scandesc;
@ -2446,6 +2453,12 @@ ExecComputeSlotInfo(ExprState *state, ExprEvalStep *op)
op->d.fetch.kind = NULL;
op->d.fetch.known_desc = NULL;
}
/* if the slot is known to always virtual we never need to deform */
if (op->d.fetch.fixed && op->d.fetch.kind == &TTSOpsVirtual)
return false;
return true;
}
/*
@ -3360,16 +3373,16 @@ ExecBuildGroupingEqual(TupleDesc ldesc, TupleDesc rdesc,
scratch.d.fetch.fixed = false;
scratch.d.fetch.known_desc = ldesc;
scratch.d.fetch.kind = lops;
ExecComputeSlotInfo(state, &scratch);
ExprEvalPushStep(state, &scratch);
if (ExecComputeSlotInfo(state, &scratch))
ExprEvalPushStep(state, &scratch);
scratch.opcode = EEOP_OUTER_FETCHSOME;
scratch.d.fetch.last_var = maxatt;
scratch.d.fetch.fixed = false;
scratch.d.fetch.known_desc = rdesc;
scratch.d.fetch.kind = rops;
ExecComputeSlotInfo(state, &scratch);
ExprEvalPushStep(state, &scratch);
if (ExecComputeSlotInfo(state, &scratch))
ExprEvalPushStep(state, &scratch);
/*
* Start comparing at the last field (least significant sort key). That's

133
src/backend/executor/execExprInterp.c
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@ -160,6 +160,12 @@ static Datum ExecJustAssignOuterVar(ExprState *state, ExprContext *econtext, boo
static Datum ExecJustAssignScanVar(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustApplyFuncToCase(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustConst(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustInnerVarVirt(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustOuterVarVirt(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustScanVarVirt(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustAssignInnerVarVirt(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustAssignOuterVarVirt(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustAssignScanVarVirt(ExprState *state, ExprContext *econtext, bool *isnull);
/*
@ -255,11 +261,45 @@ ExecReadyInterpretedExpr(ExprState *state)
return;
}
}
else if (state->steps_len == 2 &&
state->steps[0].opcode == EEOP_CONST)
else if (state->steps_len == 2)
{
state->evalfunc_private = (void *) ExecJustConst;
return;
ExprEvalOp step0 = state->steps[0].opcode;
if (step0 == EEOP_CONST)
{
state->evalfunc_private = (void *) ExecJustConst;
return;
}
else if (step0 == EEOP_INNER_VAR)
{
state->evalfunc_private = (void *) ExecJustInnerVarVirt;
return;
}
else if (step0 == EEOP_OUTER_VAR)
{
state->evalfunc_private = (void *) ExecJustOuterVarVirt;
return;
}
else if (step0 == EEOP_SCAN_VAR)
{
state->evalfunc_private = (void *) ExecJustScanVarVirt;
return;
}
else if (step0 == EEOP_ASSIGN_INNER_VAR)
{
state->evalfunc_private = (void *) ExecJustAssignInnerVarVirt;
return;
}
else if (step0 == EEOP_ASSIGN_OUTER_VAR)
{
state->evalfunc_private = (void *) ExecJustAssignOuterVarVirt;
return;
}
else if (step0 == EEOP_ASSIGN_SCAN_VAR)
{
state->evalfunc_private = (void *) ExecJustAssignScanVarVirt;
return;
}
}
#if defined(EEO_USE_COMPUTED_GOTO)
@ -2096,6 +2136,91 @@ ExecJustConst(ExprState *state, ExprContext *econtext, bool *isnull)
return op->d.constval.value;
}
/* implementation of ExecJust(Inner|Outer|Scan)VarVirt */
static pg_attribute_always_inline Datum
ExecJustVarVirtImpl(ExprState *state, TupleTableSlot *slot, bool *isnull)
{
ExprEvalStep *op = &state->steps[0];
int attnum = op->d.var.attnum;
/*
* As it is guaranteed that a virtual slot is used, there never is a need
* to perform tuple deforming (nor would it be possible). Therefore
* execExpr.c has not emitted an EEOP_*_FETCHSOME step. Verify, as much as
* possible, that that determination was accurate.
*/
Assert(TTS_IS_VIRTUAL(slot));
Assert(TTS_FIXED(slot));
Assert(attnum >= 0 && attnum < slot->tts_nvalid);
*isnull = slot->tts_isnull[attnum];
return slot->tts_values[attnum];
}
/* Like ExecJustInnerVar, optimized for virtual slots */
static Datum
ExecJustInnerVarVirt(ExprState *state, ExprContext *econtext, bool *isnull)
{
return ExecJustVarVirtImpl(state, econtext->ecxt_innertuple, isnull);
}
/* Like ExecJustOuterVar, optimized for virtual slots */
static Datum
ExecJustOuterVarVirt(ExprState *state, ExprContext *econtext, bool *isnull)
{
return ExecJustVarVirtImpl(state, econtext->ecxt_outertuple, isnull);
}
/* Like ExecJustScanVar, optimized for virtual slots */
static Datum
ExecJustScanVarVirt(ExprState *state, ExprContext *econtext, bool *isnull)
{
return ExecJustVarVirtImpl(state, econtext->ecxt_scantuple, isnull);
}
/* implementation of ExecJustAssign(Inner|Outer|Scan)VarVirt */
static pg_attribute_always_inline Datum
ExecJustAssignVarVirtImpl(ExprState *state, TupleTableSlot *inslot, bool *isnull)
{
ExprEvalStep *op = &state->steps[0];
int attnum = op->d.assign_var.attnum;
int resultnum = op->d.assign_var.resultnum;
TupleTableSlot *outslot = state->resultslot;
/* see ExecJustVarVirtImpl for comments */
Assert(TTS_IS_VIRTUAL(inslot));
Assert(TTS_FIXED(inslot));
Assert(attnum >= 0 && attnum < inslot->tts_nvalid);
outslot->tts_values[resultnum] = inslot->tts_values[attnum];
outslot->tts_isnull[resultnum] = inslot->tts_isnull[attnum];
return 0;
}
/* Like ExecJustAssignInnerVar, optimized for virtual slots */
static Datum
ExecJustAssignInnerVarVirt(ExprState *state, ExprContext *econtext, bool *isnull)
{
return ExecJustAssignVarVirtImpl(state, econtext->ecxt_innertuple, isnull);
}
/* Like ExecJustAssignOuterVar, optimized for virtual slots */
static Datum
ExecJustAssignOuterVarVirt(ExprState *state, ExprContext *econtext, bool *isnull)
{
return ExecJustAssignVarVirtImpl(state, econtext->ecxt_outertuple, isnull);
}
/* Like ExecJustAssignScanVar, optimized for virtual slots */
static Datum
ExecJustAssignScanVarVirt(ExprState *state, ExprContext *econtext, bool *isnull)
{
return ExecJustAssignVarVirtImpl(state, econtext->ecxt_scantuple, isnull);
}
#if defined(EEO_USE_COMPUTED_GOTO)
/*
* Comparator used when building address->opcode lookup table for

6
src/backend/jit/llvm/llvmjit_expr.c
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@ -287,6 +287,9 @@ llvm_compile_expr(ExprState *state)
if (op->d.fetch.fixed)
tts_ops = op->d.fetch.kind;
/* step should not have been generated */
Assert(tts_ops != &TTSOpsVirtual);
if (opcode == EEOP_INNER_FETCHSOME)
v_slot = v_innerslot;
else if (opcode == EEOP_OUTER_FETCHSOME)
@ -297,9 +300,6 @@ llvm_compile_expr(ExprState *state)
/*
* Check if all required attributes are available, or
* whether deforming is required.
*
* TODO: skip nvalid check if slot is fixed and known to
* be a virtual slot.
*/
v_nvalid =
l_load_struct_gep(b, v_slot,

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