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Invent GENERIC_PLAN option for EXPLAIN.

Browse Source 
This provides a very simple way to see the generic plan for a
parameterized query.  Without this, it's necessary to define
a prepared statement and temporarily change plan_cache_mode,
which is a bit tedious.

One thing that's a bit of a hack perhaps is that we disable
execution-time partition pruning when the GENERIC_PLAN option
is given.  That's because the pruning code may attempt to
fetch the value of one of the parameters, which would fail.

Laurenz Albe, reviewed by Julien Rouhaud, Christoph Berg,
Michel Pelletier, Jim Jones, and myself

Discussion: https://postgr.es/m/0a29b954b10b57f0d135fe12aa0909bd41883eb0.camel@cybertec.at
This commit is contained in:
Tom Lane
2023-03-24 17:07:14 -04:00
parent 5b140dc8f0
commit 3c05284d83
10 changed files with 197 additions and 20 deletions
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11
src/backend/commands/explain.c
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@ -190,6 +190,8 @@ ExplainQuery(ParseState *pstate, ExplainStmt *stmt,
es->wal = defGetBoolean(opt);
else if (strcmp(opt->defname, "settings") == 0)
es->settings = defGetBoolean(opt);
else if (strcmp(opt->defname, "generic_plan") == 0)
es->generic = defGetBoolean(opt);
else if (strcmp(opt->defname, "timing") == 0)
{
timing_set = true;
@ -227,6 +229,7 @@ ExplainQuery(ParseState *pstate, ExplainStmt *stmt,
parser_errposition(pstate, opt->location)));
}
/* check that WAL is used with EXPLAIN ANALYZE */
if (es->wal && !es->analyze)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
@ -241,6 +244,12 @@ ExplainQuery(ParseState *pstate, ExplainStmt *stmt,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("EXPLAIN option TIMING requires ANALYZE")));
/* check that GENERIC_PLAN is not used with EXPLAIN ANALYZE */
if (es->generic && es->analyze)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("EXPLAIN options ANALYZE and GENERIC_PLAN cannot be used together")));
/* if the summary was not set explicitly, set default value */
es->summary = (summary_set) ? es->summary : es->analyze;
@ -572,6 +581,8 @@ ExplainOnePlan(PlannedStmt *plannedstmt, IntoClause *into, ExplainState *es,
eflags = 0; /* default run-to-completion flags */
else
eflags = EXEC_FLAG_EXPLAIN_ONLY;
if (es->generic)
eflags |= EXEC_FLAG_EXPLAIN_GENERIC;
if (into)
eflags |= GetIntoRelEFlags(into);