--- /dev/null
+#! /usr/bin/perl
+
+use strict;
+
+my $srcpath;
+my @sources = (
+ 'src/backend/optimizer/path/allpaths.c',
+ 'src/backend/optimizer/path/joinrels.c');
+my %defs =
+ ('core.c'
+ => {protos => ['populate_joinrel_with_paths'],
+ funcs => ['set_plain_rel_pathlist',
+ 'set_append_rel_pathlist',
+ 'standard_join_search',
+ 'create_plain_partial_paths',
+ 'join_search_one_level',
+ 'make_rels_by_clause_joins',
+ 'make_rels_by_clauseless_joins',
+ 'join_is_legal',
+ 'has_join_restriction',
+ 'restriction_is_constant_false',
+ 'build_child_join_sjinfo',
+ 'try_partitionwise_join'],
+ head => core_c_head()},
+ 'make_join_rel.c'
+ => {protos => [],
+ funcs => ['make_join_rel',
+ 'populate_joinrel_with_paths'],
+ head => make_join_rel_head()});
+
+open (my $in, '-|', "objdump -W `which postgres`") || die "failed to objdump";
+while (<$in>)
+{
+ if (/DW_AT_comp_dir .*: (.*\/)src\/backend\//)
+ {
+ $srcpath = $1;
+ last;
+ }
+}
+close($in);
+
+die "source path not found" if (! defined $srcpath);
+#printf("Source path = %s\n", $srcpath);
+
+my %protos;
+my %funcs;
+my %func_is_static;
+my %func_source;
+
+for my $fname (@sources)
+{
+ my $f = $srcpath.$fname;
+ my $source;
+
+ open ($in, '<', $f) || die "failed to open $f: $!";
+ while (<$in>)
+ {
+ $source .= $_;
+ }
+
+ ## Collect static prototypes
+
+ while ($source =~ /\n(static [^\(\)\{\}]*?(\w+)(\([^\{\);]+?\);))/gsm)
+ {
+ # print "Prototype found: $2\n";
+ $protos{$2} = $1;
+ }
+
+ ## Collect function bodies
+
+ while ($source =~ /(\n\/\*\n.+?\*\/\n(static )?(.+?)\n(.+?) *\(.*?\)\n\{.+?\n\}\n)/gsm)
+ {
+ $funcs{$4} = $1;
+ $func_is_static{$4} = (defined $2);
+ $func_source{$4} = $fname;
+
+ # printf("Function found: %s$4\n", $func_is_static{$4} ? "static " : "");
+ }
+
+ close($in);
+}
+
+
+# Generate files
+for my $fname (keys %defs)
+{
+ my %d = %{$defs{$fname}};
+
+ my @protonames = @{$d{'protos'}};
+ my @funcnames = @{$d{'funcs'}};
+ my $head = $d{'head'};
+
+ print "Generate $fname.\n";
+ open (my $out, '>', $fname) || die "could not open $fname: $!";
+
+ print $out $head;
+
+ for (@protonames)
+ {
+ print " Prototype: $_\n";
+ print $out "\n";
+ die "Prototype for $_ not found" if (! defined $protos{$_});
+ print $out $protos{$_};
+ }
+
+ for (@funcnames)
+ {
+ printf(" %s function: $_@%s\n",
+ $func_is_static{$_}?"static":"public", $func_source{$_});
+ print $out "\n";
+ die "Function body for $_ not found" if (! defined $funcs{$_});
+ print $out $funcs{$_};
+ }
+
+ close($out);
+}
+
+# modify make_join_rel.c
+patch_make_join_rel();
+
+sub core_c_head()
+{
+ return << "EOS";
+/*-------------------------------------------------------------------------
+ *
+ * core.c
+ * Routines copied from PostgreSQL core distribution.
+ *
+ * The main purpose of this files is having access to static functions in core.
+ * Another purpose is tweaking functions behavior by replacing part of them by
+ * macro definitions. See at the end of pg_hint_plan.c for details. Anyway,
+ * this file *must* contain required functions without making any change.
+ *
+ * This file contains the following functions from corresponding files.
+ *
+ * src/backend/optimizer/path/allpaths.c
+ *
+ * public functions:
+ * standard_join_search(): This funcion is not static. The reason for
+ * including this function is make_rels_by_clause_joins. In order to
+ * avoid generating apparently unwanted join combination, we decided to
+ * change the behavior of make_join_rel, which is called under this
+ * function.
+ *
+ * static functions:
+ * set_plain_rel_pathlist()
+ * set_append_rel_pathlist()
+ * create_plain_partial_paths()
+ *
+ * src/backend/optimizer/path/joinrels.c
+ *
+ * public functions:
+ * join_search_one_level(): We have to modify this to call my definition of
+ * make_rels_by_clause_joins.
+ *
+ * static functions:
+ * make_rels_by_clause_joins()
+ * make_rels_by_clauseless_joins()
+ * join_is_legal()
+ * has_join_restriction()
+ * restriction_is_constant_false()
+ * build_child_join_sjinfo()
+ * try_partitionwise_join()
+ *
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *-------------------------------------------------------------------------
+ */
+EOS
+}
+
+sub make_join_rel_head
+{
+ return << "EOS";
+/*-------------------------------------------------------------------------
+ *
+ * make_join_rel.c
+ * Routines copied from PostgreSQL core distribution with some
+ * modifications.
+ *
+ * src/backend/optimizer/path/joinrels.c
+ *
+ * This file contains the following functions from corresponding files.
+ *
+ * static functions:
+ * make_join_rel()
+ * populate_joinrel_with_paths()
+ *
+ * Portions Copyright (c) 2013-2020, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/*
+ * adjust_rows: tweak estimated row numbers according to the hint.
+ */
+static double
+adjust_rows(double rows, RowsHint *hint)
+{
+ double result = 0.0; /* keep compiler quiet */
+
+ if (hint->value_type == RVT_ABSOLUTE)
+ result = hint->rows;
+ else if (hint->value_type == RVT_ADD)
+ result = rows + hint->rows;
+ else if (hint->value_type == RVT_SUB)
+ result = rows - hint->rows;
+ else if (hint->value_type == RVT_MULTI)
+ result = rows * hint->rows;
+ else
+ Assert(false); /* unrecognized rows value type */
+
+ hint->base.state = HINT_STATE_USED;
+ if (result < 1.0)
+ ereport(WARNING,
+ (errmsg("Force estimate to be at least one row, to avoid possible divide-by-zero when interpolating costs : %s",
+ hint->base.hint_str)));
+ result = clamp_row_est(result);
+ elog(DEBUG1, "adjusted rows %d to %d", (int) rows, (int) result);
+
+ return result;
+}
+EOS
+}
+
+
+sub patch_make_join_rel
+{
+ open(my $out, '|-', 'patch') || die "failed to open pipe: $!";
+
+ print $out <<"EOS";
+diff --git b/make_join_rel.c a/make_join_rel.c
+index 0e7b99f..287e7f1 100644
+--- b/make_join_rel.c
++++ a/make_join_rel.c
+@@ -126,6 +126,84 @@ make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
+ joinrel = build_join_rel(root, joinrelids, rel1, rel2, sjinfo,
+ &restrictlist);
+
++ /* !!! START: HERE IS THE PART WHICH ADDED FOR PG_HINT_PLAN !!! */
++ {
++ RowsHint *rows_hint = NULL;
++ int i;
++ RowsHint *justforme = NULL;
++ RowsHint *domultiply = NULL;
++
++ /* Search for applicable rows hint for this join node */
++ for (i = 0; i < current_hint_state->num_hints[HINT_TYPE_ROWS]; i++)
++ {
++ rows_hint = current_hint_state->rows_hints[i];
++
++ /*
++ * Skip this rows_hint if it is invalid from the first or it
++ * doesn't target any join rels.
++ */
++ if (!rows_hint->joinrelids ||
++ rows_hint->base.state == HINT_STATE_ERROR)
++ continue;
++
++ if (bms_equal(joinrelids, rows_hint->joinrelids))
++ {
++ /*
++ * This joinrel is just the target of this rows_hint, so tweak
++ * rows estimation according to the hint.
++ */
++ justforme = rows_hint;
++ }
++ else if (!(bms_is_subset(rows_hint->joinrelids, rel1->relids) ||
++ bms_is_subset(rows_hint->joinrelids, rel2->relids)) &&
++ bms_is_subset(rows_hint->joinrelids, joinrelids) &&
++ rows_hint->value_type == RVT_MULTI)
++ {
++ /*
++ * If the rows_hint's target relids is not a subset of both of
++ * component rels and is a subset of this joinrel, ths hint's
++ * targets spread over both component rels. This menas that
++ * this hint has been never applied so far and this joinrel is
++ * the first (and only) chance to fire in current join tree.
++ * Only the multiplication hint has the cumulative nature so we
++ * apply only RVT_MULTI in this way.
++ */
++ domultiply = rows_hint;
++ }
++ }
++
++ if (justforme)
++ {
++ /*
++ * If a hint just for me is found, no other adjust method is
++ * useles, but this cannot be more than twice becuase this joinrel
++ * is already adjusted by this hint.
++ */
++ if (justforme->base.state == HINT_STATE_NOTUSED)
++ joinrel->rows = adjust_rows(joinrel->rows, justforme);
++ }
++ else
++ {
++ if (domultiply)
++ {
++ /*
++ * If we have multiple routes up to this joinrel which are not
++ * applicable this hint, this multiply hint will applied more
++ * than twice. But there's no means to know of that,
++ * re-estimate the row number of this joinrel always just
++ * before applying the hint. This is a bit different from
++ * normal planner behavior but it doesn't harm so much.
++ */
++ set_joinrel_size_estimates(root, joinrel, rel1, rel2, sjinfo,
++ restrictlist);
++
++ joinrel->rows = adjust_rows(joinrel->rows, domultiply);
++ }
++
++ }
++ }
++ /* !!! END: HERE IS THE PART WHICH ADDED FOR PG_HINT_PLAN !!! */
++
+ /*
+ * If we've already proven this join is empty, we needn't consider any
+ * more paths for it.
+EOS
+}
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