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Improve EXPLAIN's display of window functions.

Browse Source 
Up to now we just punted on showing the window definitions used
in a plan, with window function calls represented as "OVER (?)".
To improve that, show the window definition implemented by each
WindowAgg plan node, and reference their window names in OVER.
For nameless window clauses generated by "OVER (...)", assign
unique names w1, w2, etc.

In passing, re-order the properties shown for a WindowAgg node
so that the Run Condition (if any) appears after the Window
property and before the Filter (if any).  This seems more
sensible since the Run Condition is associated with the Window
and acts before the Filter.

Thanks to David G. Johnston and Álvaro Herrera for design
suggestions.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/144530.1741469955@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2025-03-11 11:19:54 -04:00
parent 426ea61117
commit 8b1b342544
18 changed files with 598 additions and 253 deletions
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150
src/backend/utils/adt/ruleutils.c
View File

@@ -441,6 +441,9 @@ static void get_rule_orderby(List *orderList, List *targetList,
static void get_rule_windowclause(Query *query, deparse_context *context);
static void get_rule_windowspec(WindowClause *wc, List *targetList,
deparse_context *context);
static void get_window_frame_options(int frameOptions,
Node *startOffset, Node *endOffset,
deparse_context *context);
static char *get_variable(Var *var, int levelsup, bool istoplevel,
deparse_context *context);
static void get_special_variable(Node *node, deparse_context *context,
@@ -6811,45 +6814,64 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
{
if (needspace)
appendStringInfoChar(buf, ' ');
if (wc->frameOptions & FRAMEOPTION_RANGE)
get_window_frame_options(wc->frameOptions,
wc->startOffset, wc->endOffset,
context);
}
appendStringInfoChar(buf, ')');
}
/*
* Append the description of a window's framing options to context->buf
*/
static void
get_window_frame_options(int frameOptions,
Node *startOffset, Node *endOffset,
deparse_context *context)
{
StringInfo buf = context->buf;
if (frameOptions & FRAMEOPTION_NONDEFAULT)
{
if (frameOptions & FRAMEOPTION_RANGE)
appendStringInfoString(buf, "RANGE ");
else if (wc->frameOptions & FRAMEOPTION_ROWS)
else if (frameOptions & FRAMEOPTION_ROWS)
appendStringInfoString(buf, "ROWS ");
else if (wc->frameOptions & FRAMEOPTION_GROUPS)
else if (frameOptions & FRAMEOPTION_GROUPS)
appendStringInfoString(buf, "GROUPS ");
else
Assert(false);
if (wc->frameOptions & FRAMEOPTION_BETWEEN)
if (frameOptions & FRAMEOPTION_BETWEEN)
appendStringInfoString(buf, "BETWEEN ");
if (wc->frameOptions & FRAMEOPTION_START_UNBOUNDED_PRECEDING)
if (frameOptions & FRAMEOPTION_START_UNBOUNDED_PRECEDING)
appendStringInfoString(buf, "UNBOUNDED PRECEDING ");
else if (wc->frameOptions & FRAMEOPTION_START_CURRENT_ROW)
else if (frameOptions & FRAMEOPTION_START_CURRENT_ROW)
appendStringInfoString(buf, "CURRENT ROW ");
else if (wc->frameOptions & FRAMEOPTION_START_OFFSET)
else if (frameOptions & FRAMEOPTION_START_OFFSET)
{
get_rule_expr(wc->startOffset, context, false);
if (wc->frameOptions & FRAMEOPTION_START_OFFSET_PRECEDING)
get_rule_expr(startOffset, context, false);
if (frameOptions & FRAMEOPTION_START_OFFSET_PRECEDING)
appendStringInfoString(buf, " PRECEDING ");
else if (wc->frameOptions & FRAMEOPTION_START_OFFSET_FOLLOWING)
else if (frameOptions & FRAMEOPTION_START_OFFSET_FOLLOWING)
appendStringInfoString(buf, " FOLLOWING ");
else
Assert(false);
}
else
Assert(false);
if (wc->frameOptions & FRAMEOPTION_BETWEEN)
if (frameOptions & FRAMEOPTION_BETWEEN)
{
appendStringInfoString(buf, "AND ");
if (wc->frameOptions & FRAMEOPTION_END_UNBOUNDED_FOLLOWING)
if (frameOptions & FRAMEOPTION_END_UNBOUNDED_FOLLOWING)
appendStringInfoString(buf, "UNBOUNDED FOLLOWING ");
else if (wc->frameOptions & FRAMEOPTION_END_CURRENT_ROW)
else if (frameOptions & FRAMEOPTION_END_CURRENT_ROW)
appendStringInfoString(buf, "CURRENT ROW ");
else if (wc->frameOptions & FRAMEOPTION_END_OFFSET)
else if (frameOptions & FRAMEOPTION_END_OFFSET)
{
get_rule_expr(wc->endOffset, context, false);
if (wc->frameOptions & FRAMEOPTION_END_OFFSET_PRECEDING)
get_rule_expr(endOffset, context, false);
if (frameOptions & FRAMEOPTION_END_OFFSET_PRECEDING)
appendStringInfoString(buf, " PRECEDING ");
else if (wc->frameOptions & FRAMEOPTION_END_OFFSET_FOLLOWING)
else if (frameOptions & FRAMEOPTION_END_OFFSET_FOLLOWING)
appendStringInfoString(buf, " FOLLOWING ");
else
Assert(false);
@@ -6857,16 +6879,46 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
else
Assert(false);
}
if (wc->frameOptions & FRAMEOPTION_EXCLUDE_CURRENT_ROW)
if (frameOptions & FRAMEOPTION_EXCLUDE_CURRENT_ROW)
appendStringInfoString(buf, "EXCLUDE CURRENT ROW ");
else if (wc->frameOptions & FRAMEOPTION_EXCLUDE_GROUP)
else if (frameOptions & FRAMEOPTION_EXCLUDE_GROUP)
appendStringInfoString(buf, "EXCLUDE GROUP ");
else if (wc->frameOptions & FRAMEOPTION_EXCLUDE_TIES)
else if (frameOptions & FRAMEOPTION_EXCLUDE_TIES)
appendStringInfoString(buf, "EXCLUDE TIES ");
/* we will now have a trailing space; remove it */
buf->len--;
buf->data[--(buf->len)] = '\0';
}
appendStringInfoChar(buf, ')');
}
/*
* Return the description of a window's framing options as a palloc'd string
*/
char *
get_window_frame_options_for_explain(int frameOptions,
Node *startOffset, Node *endOffset,
List *dpcontext, bool forceprefix)
{
StringInfoData buf;
deparse_context context;
initStringInfo(&buf);
context.buf = &buf;
context.namespaces = dpcontext;
context.resultDesc = NULL;
context.targetList = NIL;
context.windowClause = NIL;
context.varprefix = forceprefix;
context.prettyFlags = 0;
context.wrapColumn = WRAP_COLUMN_DEFAULT;
context.indentLevel = 0;
context.colNamesVisible = true;
context.inGroupBy = false;
context.varInOrderBy = false;
context.appendparents = NULL;
get_window_frame_options(frameOptions, startOffset, endOffset, &context);
return buf.data;
}
/* ----------
@@ -11030,30 +11082,50 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
appendStringInfoString(buf, ") OVER ");
foreach(l, context->windowClause)
if (context->windowClause)
{
WindowClause *wc = (WindowClause *) lfirst(l);
if (wc->winref == wfunc->winref)
/* Query-decompilation case: search the windowClause list */
foreach(l, context->windowClause)
{
if (wc->name)
appendStringInfoString(buf, quote_identifier(wc->name));
else
get_rule_windowspec(wc, context->targetList, context);
break;
WindowClause *wc = (WindowClause *) lfirst(l);
if (wc->winref == wfunc->winref)
{
if (wc->name)
appendStringInfoString(buf, quote_identifier(wc->name));
else
get_rule_windowspec(wc, context->targetList, context);
break;
}
}
}
if (l == NULL)
{
if (context->windowClause)
if (l == NULL)
elog(ERROR, "could not find window clause for winref %u",
wfunc->winref);
}
else
{
/*
* In EXPLAIN, we don't have window context information available, so
* we have to settle for this:
* In EXPLAIN, search the namespace stack for a matching WindowAgg
* node (probably it's always the first entry), and print winname.
*/
appendStringInfoString(buf, "(?)");
foreach(l, context->namespaces)
{
deparse_namespace *dpns = (deparse_namespace *) lfirst(l);
if (dpns->plan && IsA(dpns->plan, WindowAgg))
{
WindowAgg *wagg = (WindowAgg *) dpns->plan;
if (wagg->winref == wfunc->winref)
{
appendStringInfoString(buf, quote_identifier(wagg->winname));
break;
}
}
}
if (l == NULL)
elog(ERROR, "could not find window clause for winref %u",
wfunc->winref);
}
}