Move inheritance expansion code into its own file

This commit moves expand_inherited_tables and underlings from
optimizer/prep/prepunionc.c to optimizer/utils/inherit.c.
Also, all of the AppendRelInfo-based expression manipulation routines
are moved to optimizer/utils/appendinfo.c.

No functional code changes.  One exception is the introduction of
make_append_rel_info, but that's still just moving around code.

Also, stop including <limits.h> in prepunion.c, which no longer needs
it since 3fc6e2d7f5b6.  I (Álvaro) noticed this because Amit was copying
that to inherit.c, which likewise doesn't need it.

Author: Amit Langote
Discussion: https://postgr.es/m/3be67028-a00a-502c-199a-da00eec8fb6e@lab.ntt.co.jp

5 files changed, 1270 insertions, 2 deletions

diff --git a/src/backend/optimizer/util/Makefile b/src/backend/optimizer/util/Makefile
index c54d0a690d8..adffb012267 100644
--- a/src/backend/optimizer/util/Makefile
+++ b/src/backend/optimizer/util/Makefile
@@ -12,7 +12,8 @@ subdir = src/backend/optimizer/util
 top_builddir = ../../../..
 include $(top_builddir)/src/Makefile.global
 
-OBJS = clauses.o joininfo.o orclauses.o pathnode.o placeholder.o \
-       plancat.o predtest.o relnode.o restrictinfo.o tlist.o var.o
+OBJS = appendinfo.o clauses.o inherit.o joininfo.o orclauses.o pathnode.o \
+       placeholder.o plancat.o predtest.o relnode.o restrictinfo.o tlist.o \
+       var.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/optimizer/util/appendinfo.c b/src/backend/optimizer/util/appendinfo.c
new file mode 100644
index 00000000000..d48e3a09b3e
--- /dev/null
+++ b/src/backend/optimizer/util/appendinfo.c
@@ -0,0 +1,826 @@
+/*-------------------------------------------------------------------------
+ *
+ * appendinfo.c
+ *	  Routines for mapping between append parent(s) and children
+ *
+ * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/optimizer/path/appendinfo.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/htup_details.h"
+#include "access/sysattr.h"
+#include "nodes/makefuncs.h"
+#include "nodes/nodeFuncs.h"
+#include "optimizer/appendinfo.h"
+#include "parser/parsetree.h"
+#include "utils/rel.h"
+#include "utils/lsyscache.h"
+#include "utils/syscache.h"
+
+
+typedef struct
+{
+	PlannerInfo *root;
+	int			nappinfos;
+	AppendRelInfo **appinfos;
+} adjust_appendrel_attrs_context;
+
+static void make_inh_translation_list(Relation oldrelation,
+						  Relation newrelation,
+						  Index newvarno,
+						  List **translated_vars);
+static Node *adjust_appendrel_attrs_mutator(Node *node,
+							   adjust_appendrel_attrs_context *context);
+static Relids adjust_child_relids(Relids relids, int nappinfos,
+					AppendRelInfo **appinfos);
+static List *adjust_inherited_tlist(List *tlist,
+					   AppendRelInfo *context);
+
+
+/*
+ * make_append_rel_info
+ *	  Build an AppendRelInfo for the parent-child pair
+ */
+AppendRelInfo *
+make_append_rel_info(Relation parentrel, Relation childrel,
+					 Index parentRTindex, Index childRTindex)
+{
+	AppendRelInfo *appinfo = makeNode(AppendRelInfo);
+
+	appinfo->parent_relid = parentRTindex;
+	appinfo->child_relid = childRTindex;
+	appinfo->parent_reltype = parentrel->rd_rel->reltype;
+	appinfo->child_reltype = childrel->rd_rel->reltype;
+	make_inh_translation_list(parentrel, childrel, childRTindex,
+							  &appinfo->translated_vars);
+	appinfo->parent_reloid = RelationGetRelid(parentrel);
+
+	return appinfo;
+}
+
+/*
+ * make_inh_translation_list
+ *	  Build the list of translations from parent Vars to child Vars for
+ *	  an inheritance child.
+ *
+ * For paranoia's sake, we match type/collation as well as attribute name.
+ */
+static void
+make_inh_translation_list(Relation oldrelation, Relation newrelation,
+						  Index newvarno,
+						  List **translated_vars)
+{
+	List	   *vars = NIL;
+	TupleDesc	old_tupdesc = RelationGetDescr(oldrelation);
+	TupleDesc	new_tupdesc = RelationGetDescr(newrelation);
+	Oid			new_relid = RelationGetRelid(newrelation);
+	int			oldnatts = old_tupdesc->natts;
+	int			newnatts = new_tupdesc->natts;
+	int			old_attno;
+	int			new_attno = 0;
+
+	for (old_attno = 0; old_attno < oldnatts; old_attno++)
+	{
+		Form_pg_attribute att;
+		char	   *attname;
+		Oid			atttypid;
+		int32		atttypmod;
+		Oid			attcollation;
+
+		att = TupleDescAttr(old_tupdesc, old_attno);
+		if (att->attisdropped)
+		{
+			/* Just put NULL into this list entry */
+			vars = lappend(vars, NULL);
+			continue;
+		}
+		attname = NameStr(att->attname);
+		atttypid = att->atttypid;
+		atttypmod = att->atttypmod;
+		attcollation = att->attcollation;
+
+		/*
+		 * When we are generating the "translation list" for the parent table
+		 * of an inheritance set, no need to search for matches.
+		 */
+		if (oldrelation == newrelation)
+		{
+			vars = lappend(vars, makeVar(newvarno,
+										 (AttrNumber) (old_attno + 1),
+										 atttypid,
+										 atttypmod,
+										 attcollation,
+										 0));
+			continue;
+		}
+
+		/*
+		 * Otherwise we have to search for the matching column by name.
+		 * There's no guarantee it'll have the same column position, because
+		 * of cases like ALTER TABLE ADD COLUMN and multiple inheritance.
+		 * However, in simple cases, the relative order of columns is mostly
+		 * the same in both relations, so try the column of newrelation that
+		 * follows immediately after the one that we just found, and if that
+		 * fails, let syscache handle it.
+		 */
+		if (new_attno >= newnatts ||
+			(att = TupleDescAttr(new_tupdesc, new_attno))->attisdropped ||
+			strcmp(attname, NameStr(att->attname)) != 0)
+		{
+			HeapTuple	newtup;
+
+			newtup = SearchSysCacheAttName(new_relid, attname);
+			if (!newtup)
+				elog(ERROR, "could not find inherited attribute \"%s\" of relation \"%s\"",
+					 attname, RelationGetRelationName(newrelation));
+			new_attno = ((Form_pg_attribute) GETSTRUCT(newtup))->attnum - 1;
+			ReleaseSysCache(newtup);
+
+			att = TupleDescAttr(new_tupdesc, new_attno);
+		}
+
+		/* Found it, check type and collation match */
+		if (atttypid != att->atttypid || atttypmod != att->atttypmod)
+			elog(ERROR, "attribute \"%s\" of relation \"%s\" does not match parent's type",
+				 attname, RelationGetRelationName(newrelation));
+		if (attcollation != att->attcollation)
+			elog(ERROR, "attribute \"%s\" of relation \"%s\" does not match parent's collation",
+				 attname, RelationGetRelationName(newrelation));
+
+		vars = lappend(vars, makeVar(newvarno,
+									 (AttrNumber) (new_attno + 1),
+									 atttypid,
+									 atttypmod,
+									 attcollation,
+									 0));
+		new_attno++;
+	}
+
+	*translated_vars = vars;
+}
+
+/*
+ * translate_col_privs
+ *	  Translate a bitmapset representing per-column privileges from the
+ *	  parent rel's attribute numbering to the child's.
+ *
+ * The only surprise here is that we don't translate a parent whole-row
+ * reference into a child whole-row reference.  That would mean requiring
+ * permissions on all child columns, which is overly strict, since the
+ * query is really only going to reference the inherited columns.  Instead
+ * we set the per-column bits for all inherited columns.
+ */
+Bitmapset *
+translate_col_privs(const Bitmapset *parent_privs,
+					List *translated_vars)
+{
+	Bitmapset  *child_privs = NULL;
+	bool		whole_row;
+	int			attno;
+	ListCell   *lc;
+
+	/* System attributes have the same numbers in all tables */
+	for (attno = FirstLowInvalidHeapAttributeNumber + 1; attno < 0; attno++)
+	{
+		if (bms_is_member(attno - FirstLowInvalidHeapAttributeNumber,
+						  parent_privs))
+			child_privs = bms_add_member(child_privs,
+										 attno - FirstLowInvalidHeapAttributeNumber);
+	}
+
+	/* Check if parent has whole-row reference */
+	whole_row = bms_is_member(InvalidAttrNumber - FirstLowInvalidHeapAttributeNumber,
+							  parent_privs);
+
+	/* And now translate the regular user attributes, using the vars list */
+	attno = InvalidAttrNumber;
+	foreach(lc, translated_vars)
+	{
+		Var		   *var = lfirst_node(Var, lc);
+
+		attno++;
+		if (var == NULL)		/* ignore dropped columns */
+			continue;
+		if (whole_row ||
+			bms_is_member(attno - FirstLowInvalidHeapAttributeNumber,
+						  parent_privs))
+			child_privs = bms_add_member(child_privs,
+										 var->varattno - FirstLowInvalidHeapAttributeNumber);
+	}
+
+	return child_privs;
+}
+
+/*
+ * adjust_appendrel_attrs
+ *	  Copy the specified query or expression and translate Vars referring to a
+ *	  parent rel to refer to the corresponding child rel instead.  We also
+ *	  update rtindexes appearing outside Vars, such as resultRelation and
+ *	  jointree relids.
+ *
+ * Note: this is only applied after conversion of sublinks to subplans,
+ * so we don't need to cope with recursion into sub-queries.
+ *
+ * Note: this is not hugely different from what pullup_replace_vars() does;
+ * maybe we should try to fold the two routines together.
+ */
+Node *
+adjust_appendrel_attrs(PlannerInfo *root, Node *node, int nappinfos,
+					   AppendRelInfo **appinfos)
+{
+	Node	   *result;
+	adjust_appendrel_attrs_context context;
+
+	context.root = root;
+	context.nappinfos = nappinfos;
+	context.appinfos = appinfos;
+
+	/* If there's nothing to adjust, don't call this function. */
+	Assert(nappinfos >= 1 && appinfos != NULL);
+
+	/*
+	 * Must be prepared to start with a Query or a bare expression tree.
+	 */
+	if (node && IsA(node, Query))
+	{
+		Query	   *newnode;
+		int			cnt;
+
+		newnode = query_tree_mutator((Query *) node,
+									 adjust_appendrel_attrs_mutator,
+									 (void *) &context,
+									 QTW_IGNORE_RC_SUBQUERIES);
+		for (cnt = 0; cnt < nappinfos; cnt++)
+		{
+			AppendRelInfo *appinfo = appinfos[cnt];
+
+			if (newnode->resultRelation == appinfo->parent_relid)
+			{
+				newnode->resultRelation = appinfo->child_relid;
+				/* Fix tlist resnos too, if it's inherited UPDATE */
+				if (newnode->commandType == CMD_UPDATE)
+					newnode->targetList =
+						adjust_inherited_tlist(newnode->targetList,
+											   appinfo);
+				break;
+			}
+		}
+
+		result = (Node *) newnode;
+	}
+	else
+		result = adjust_appendrel_attrs_mutator(node, &context);
+
+	return result;
+}
+
+static Node *
+adjust_appendrel_attrs_mutator(Node *node,
+							   adjust_appendrel_attrs_context *context)
+{
+	AppendRelInfo **appinfos = context->appinfos;
+	int			nappinfos = context->nappinfos;
+	int			cnt;
+
+	if (node == NULL)
+		return NULL;
+	if (IsA(node, Var))
+	{
+		Var		   *var = (Var *) copyObject(node);
+		AppendRelInfo *appinfo = NULL;
+
+		for (cnt = 0; cnt < nappinfos; cnt++)
+		{
+			if (var->varno == appinfos[cnt]->parent_relid)
+			{
+				appinfo = appinfos[cnt];
+				break;
+			}
+		}
+
+		if (var->varlevelsup == 0 && appinfo)
+		{
+			var->varno = appinfo->child_relid;
+			var->varnoold = appinfo->child_relid;
+			if (var->varattno > 0)
+			{
+				Node	   *newnode;
+
+				if (var->varattno > list_length(appinfo->translated_vars))
+					elog(ERROR, "attribute %d of relation \"%s\" does not exist",
+						 var->varattno, get_rel_name(appinfo->parent_reloid));
+				newnode = copyObject(list_nth(appinfo->translated_vars,
+											  var->varattno - 1));
+				if (newnode == NULL)
+					elog(ERROR, "attribute %d of relation \"%s\" does not exist",
+						 var->varattno, get_rel_name(appinfo->parent_reloid));
+				return newnode;
+			}
+			else if (var->varattno == 0)
+			{
+				/*
+				 * Whole-row Var: if we are dealing with named rowtypes, we
+				 * can use a whole-row Var for the child table plus a coercion
+				 * step to convert the tuple layout to the parent's rowtype.
+				 * Otherwise we have to generate a RowExpr.
+				 */
+				if (OidIsValid(appinfo->child_reltype))
+				{
+					Assert(var->vartype == appinfo->parent_reltype);
+					if (appinfo->parent_reltype != appinfo->child_reltype)
+					{
+						ConvertRowtypeExpr *r = makeNode(ConvertRowtypeExpr);
+
+						r->arg = (Expr *) var;
+						r->resulttype = appinfo->parent_reltype;
+						r->convertformat = COERCE_IMPLICIT_CAST;
+						r->location = -1;
+						/* Make sure the Var node has the right type ID, too */
+						var->vartype = appinfo->child_reltype;
+						return (Node *) r;
+					}
+				}
+				else
+				{
+					/*
+					 * Build a RowExpr containing the translated variables.
+					 *
+					 * In practice var->vartype will always be RECORDOID here,
+					 * so we need to come up with some suitable column names.
+					 * We use the parent RTE's column names.
+					 *
+					 * Note: we can't get here for inheritance cases, so there
+					 * is no need to worry that translated_vars might contain
+					 * some dummy NULLs.
+					 */
+					RowExpr    *rowexpr;
+					List	   *fields;
+					RangeTblEntry *rte;
+
+					rte = rt_fetch(appinfo->parent_relid,
+								   context->root->parse->rtable);
+					fields = copyObject(appinfo->translated_vars);
+					rowexpr = makeNode(RowExpr);
+					rowexpr->args = fields;
+					rowexpr->row_typeid = var->vartype;
+					rowexpr->row_format = COERCE_IMPLICIT_CAST;
+					rowexpr->colnames = copyObject(rte->eref->colnames);
+					rowexpr->location = -1;
+
+					return (Node *) rowexpr;
+				}
+			}
+			/* system attributes don't need any other translation */
+		}
+		return (Node *) var;
+	}
+	if (IsA(node, CurrentOfExpr))
+	{
+		CurrentOfExpr *cexpr = (CurrentOfExpr *) copyObject(node);
+
+		for (cnt = 0; cnt < nappinfos; cnt++)
+		{
+			AppendRelInfo *appinfo = appinfos[cnt];
+
+			if (cexpr->cvarno == appinfo->parent_relid)
+			{
+				cexpr->cvarno = appinfo->child_relid;
+				break;
+			}
+		}
+		return (Node *) cexpr;
+	}
+	if (IsA(node, RangeTblRef))
+	{
+		RangeTblRef *rtr = (RangeTblRef *) copyObject(node);
+
+		for (cnt = 0; cnt < nappinfos; cnt++)
+		{
+			AppendRelInfo *appinfo = appinfos[cnt];
+
+			if (rtr->rtindex == appinfo->parent_relid)
+			{
+				rtr->rtindex = appinfo->child_relid;
+				break;
+			}
+		}
+		return (Node *) rtr;
+	}
+	if (IsA(node, JoinExpr))
+	{
+		/* Copy the JoinExpr node with correct mutation of subnodes */
+		JoinExpr   *j;
+		AppendRelInfo *appinfo;
+
+		j = (JoinExpr *) expression_tree_mutator(node,
+												 adjust_appendrel_attrs_mutator,
+												 (void *) context);
+		/* now fix JoinExpr's rtindex (probably never happens) */
+		for (cnt = 0; cnt < nappinfos; cnt++)
+		{
+			appinfo = appinfos[cnt];
+
+			if (j->rtindex == appinfo->parent_relid)
+			{
+				j->rtindex = appinfo->child_relid;
+				break;
+			}
+		}
+		return (Node *) j;
+	}
+	if (IsA(node, PlaceHolderVar))
+	{
+		/* Copy the PlaceHolderVar node with correct mutation of subnodes */
+		PlaceHolderVar *phv;
+
+		phv = (PlaceHolderVar *) expression_tree_mutator(node,
+														 adjust_appendrel_attrs_mutator,
+														 (void *) context);
+		/* now fix PlaceHolderVar's relid sets */
+		if (phv->phlevelsup == 0)
+			phv->phrels = adjust_child_relids(phv->phrels, context->nappinfos,
+											  context->appinfos);
+		return (Node *) phv;
+	}
+	/* Shouldn't need to handle planner auxiliary nodes here */
+	Assert(!IsA(node, SpecialJoinInfo));
+	Assert(!IsA(node, AppendRelInfo));
+	Assert(!IsA(node, PlaceHolderInfo));
+	Assert(!IsA(node, MinMaxAggInfo));
+
+	/*
+	 * We have to process RestrictInfo nodes specially.  (Note: although
+	 * set_append_rel_pathlist will hide RestrictInfos in the parent's
+	 * baserestrictinfo list from us, it doesn't hide those in joininfo.)
+	 */
+	if (IsA(node, RestrictInfo))
+	{
+		RestrictInfo *oldinfo = (RestrictInfo *) node;
+		RestrictInfo *newinfo = makeNode(RestrictInfo);
+
+		/* Copy all flat-copiable fields */
+		memcpy(newinfo, oldinfo, sizeof(RestrictInfo));
+
+		/* Recursively fix the clause itself */
+		newinfo->clause = (Expr *)
+			adjust_appendrel_attrs_mutator((Node *) oldinfo->clause, context);
+
+		/* and the modified version, if an OR clause */
+		newinfo->orclause = (Expr *)
+			adjust_appendrel_attrs_mutator((Node *) oldinfo->orclause, context);
+
+		/* adjust relid sets too */
+		newinfo->clause_relids = adjust_child_relids(oldinfo->clause_relids,
+													 context->nappinfos,
+													 context->appinfos);
+		newinfo->required_relids = adjust_child_relids(oldinfo->required_relids,
+													   context->nappinfos,
+													   context->appinfos);
+		newinfo->outer_relids = adjust_child_relids(oldinfo->outer_relids,
+													context->nappinfos,
+													context->appinfos);
+		newinfo->nullable_relids = adjust_child_relids(oldinfo->nullable_relids,
+													   context->nappinfos,
+													   context->appinfos);
+		newinfo->left_relids = adjust_child_relids(oldinfo->left_relids,
+												   context->nappinfos,
+												   context->appinfos);
+		newinfo->right_relids = adjust_child_relids(oldinfo->right_relids,
+													context->nappinfos,
+													context->appinfos);
+
+		/*
+		 * Reset cached derivative fields, since these might need to have
+		 * different values when considering the child relation.  Note we
+		 * don't reset left_ec/right_ec: each child variable is implicitly
+		 * equivalent to its parent, so still a member of the same EC if any.
+		 */
+		newinfo->eval_cost.startup = -1;
+		newinfo->norm_selec = -1;
+		newinfo->outer_selec = -1;
+		newinfo->left_em = NULL;
+		newinfo->right_em = NULL;
+		newinfo->scansel_cache = NIL;
+		newinfo->left_bucketsize = -1;
+		newinfo->right_bucketsize = -1;
+		newinfo->left_mcvfreq = -1;
+		newinfo->right_mcvfreq = -1;
+
+		return (Node *) newinfo;
+	}
+
+	/*
+	 * NOTE: we do not need to recurse into sublinks, because they should
+	 * already have been converted to subplans before we see them.
+	 */
+	Assert(!IsA(node, SubLink));
+	Assert(!IsA(node, Query));
+
+	return expression_tree_mutator(node, adjust_appendrel_attrs_mutator,
+								   (void *) context);
+}
+
+/*
+ * Substitute child relids for parent relids in a Relid set.  The array of
+ * appinfos specifies the substitutions to be performed.
+ */
+static Relids
+adjust_child_relids(Relids relids, int nappinfos, AppendRelInfo **appinfos)
+{
+	Bitmapset  *result = NULL;
+	int			cnt;
+
+	for (cnt = 0; cnt < nappinfos; cnt++)
+	{
+		AppendRelInfo *appinfo = appinfos[cnt];
+
+		/* Remove parent, add child */
+		if (bms_is_member(appinfo->parent_relid, relids))
+		{
+			/* Make a copy if we are changing the set. */
+			if (!result)
+				result = bms_copy(relids);
+
+			result = bms_del_member(result, appinfo->parent_relid);
+			result = bms_add_member(result, appinfo->child_relid);
+		}
+	}
+
+	/* If we made any changes, return the modified copy. */
+	if (result)
+		return result;
+
+	/* Otherwise, return the original set without modification. */
+	return relids;
+}
+
+/*
+ * Replace any relid present in top_parent_relids with its child in
+ * child_relids. Members of child_relids can be multiple levels below top
+ * parent in the partition hierarchy.
+ */
+Relids
+adjust_child_relids_multilevel(PlannerInfo *root, Relids relids,
+							   Relids child_relids, Relids top_parent_relids)
+{
+	AppendRelInfo **appinfos;
+	int			nappinfos;
+	Relids		parent_relids = NULL;
+	Relids		result;
+	Relids		tmp_result = NULL;
+	int			cnt;
+
+	/*
+	 * If the given relids set doesn't contain any of the top parent relids,
+	 * it will remain unchanged.
+	 */
+	if (!bms_overlap(relids, top_parent_relids))
+		return relids;
+
+	appinfos = find_appinfos_by_relids(root, child_relids, &nappinfos);
+
+	/* Construct relids set for the immediate parent of the given child. */
+	for (cnt = 0; cnt < nappinfos; cnt++)
+	{
+		AppendRelInfo *appinfo = appinfos[cnt];
+
+		parent_relids = bms_add_member(parent_relids, appinfo->parent_relid);
+	}
+
+	/* Recurse if immediate parent is not the top parent. */
+	if (!bms_equal(parent_relids, top_parent_relids))
+	{
+		tmp_result = adjust_child_relids_multilevel(root, relids,
+													parent_relids,
+													top_parent_relids);
+		relids = tmp_result;
+	}
+
+	result = adjust_child_relids(relids, nappinfos, appinfos);
+
+	/* Free memory consumed by any intermediate result. */
+	if (tmp_result)
+		bms_free(tmp_result);
+	bms_free(parent_relids);
+	pfree(appinfos);
+
+	return result;
+}
+
+/*
+ * Adjust the targetlist entries of an inherited UPDATE operation
+ *
+ * The expressions have already been fixed, but we have to make sure that
+ * the target resnos match the child table (they may not, in the case of
+ * a column that was added after-the-fact by ALTER TABLE).  In some cases
+ * this can force us to re-order the tlist to preserve resno ordering.
+ * (We do all this work in special cases so that preptlist.c is fast for
+ * the typical case.)
+ *
+ * The given tlist has already been through expression_tree_mutator;
+ * therefore the TargetEntry nodes are fresh copies that it's okay to
+ * scribble on.
+ *
+ * Note that this is not needed for INSERT because INSERT isn't inheritable.
+ */
+static List *
+adjust_inherited_tlist(List *tlist, AppendRelInfo *context)
+{
+	bool		changed_it = false;
+	ListCell   *tl;
+	List	   *new_tlist;
+	bool		more;
+	int			attrno;
+
+	/* This should only happen for an inheritance case, not UNION ALL */
+	Assert(OidIsValid(context->parent_reloid));
+
+	/* Scan tlist and update resnos to match attnums of child rel */
+	foreach(tl, tlist)
+	{
+		TargetEntry *tle = (TargetEntry *) lfirst(tl);
+		Var		   *childvar;
+
+		if (tle->resjunk)
+			continue;			/* ignore junk items */
+
+		/* Look up the translation of this column: it must be a Var */
+		if (tle->resno <= 0 ||
+			tle->resno > list_length(context->translated_vars))
+			elog(ERROR, "attribute %d of relation \"%s\" does not exist",
+				 tle->resno, get_rel_name(context->parent_reloid));
+		childvar = (Var *) list_nth(context->translated_vars, tle->resno - 1);
+		if (childvar == NULL || !IsA(childvar, Var))
+			elog(ERROR, "attribute %d of relation \"%s\" does not exist",
+				 tle->resno, get_rel_name(context->parent_reloid));
+
+		if (tle->resno != childvar->varattno)
+		{
+			tle->resno = childvar->varattno;
+			changed_it = true;
+		}
+	}
+
+	/*
+	 * If we changed anything, re-sort the tlist by resno, and make sure
+	 * resjunk entries have resnos above the last real resno.  The sort
+	 * algorithm is a bit stupid, but for such a seldom-taken path, small is
+	 * probably better than fast.
+	 */
+	if (!changed_it)
+		return tlist;
+
+	new_tlist = NIL;
+	more = true;
+	for (attrno = 1; more; attrno++)
+	{
+		more = false;
+		foreach(tl, tlist)
+		{
+			TargetEntry *tle = (TargetEntry *) lfirst(tl);
+
+			if (tle->resjunk)
+				continue;		/* ignore junk items */
+
+			if (tle->resno == attrno)
+				new_tlist = lappend(new_tlist, tle);
+			else if (tle->resno > attrno)
+				more = true;
+		}
+	}
+
+	foreach(tl, tlist)
+	{
+		TargetEntry *tle = (TargetEntry *) lfirst(tl);
+
+		if (!tle->resjunk)
+			continue;			/* here, ignore non-junk items */
+
+		tle->resno = attrno;
+		new_tlist = lappend(new_tlist, tle);
+		attrno++;
+	}
+
+	return new_tlist;
+}
+
+/*
+ * adjust_appendrel_attrs_multilevel
+ *	  Apply Var translations from a toplevel appendrel parent down to a child.
+ *
+ * In some cases we need to translate expressions referencing a parent relation
+ * to reference an appendrel child that's multiple levels removed from it.
+ */
+Node *
+adjust_appendrel_attrs_multilevel(PlannerInfo *root, Node *node,
+								  Relids child_relids,
+								  Relids top_parent_relids)
+{
+	AppendRelInfo **appinfos;
+	Bitmapset  *parent_relids = NULL;
+	int			nappinfos;
+	int			cnt;
+
+	Assert(bms_num_members(child_relids) == bms_num_members(top_parent_relids));
+
+	appinfos = find_appinfos_by_relids(root, child_relids, &nappinfos);
+
+	/* Construct relids set for the immediate parent of given child. */
+	for (cnt = 0; cnt < nappinfos; cnt++)
+	{
+		AppendRelInfo *appinfo = appinfos[cnt];
+
+		parent_relids = bms_add_member(parent_relids, appinfo->parent_relid);
+	}
+
+	/* Recurse if immediate parent is not the top parent. */
+	if (!bms_equal(parent_relids, top_parent_relids))
+		node = adjust_appendrel_attrs_multilevel(root, node, parent_relids,
+												 top_parent_relids);
+
+	/* Now translate for this child */
+	node = adjust_appendrel_attrs(root, node, nappinfos, appinfos);
+
+	pfree(appinfos);
+
+	return node;
+}
+
+/*
+ * Construct the SpecialJoinInfo for a child-join by translating
+ * SpecialJoinInfo for the join between parents. left_relids and right_relids
+ * are the relids of left and right side of the join respectively.
+ */
+SpecialJoinInfo *
+build_child_join_sjinfo(PlannerInfo *root, SpecialJoinInfo *parent_sjinfo,
+						Relids left_relids, Relids right_relids)
+{
+	SpecialJoinInfo *sjinfo = makeNode(SpecialJoinInfo);
+	AppendRelInfo **left_appinfos;
+	int			left_nappinfos;
+	AppendRelInfo **right_appinfos;
+	int			right_nappinfos;
+
+	memcpy(sjinfo, parent_sjinfo, sizeof(SpecialJoinInfo));
+	left_appinfos = find_appinfos_by_relids(root, left_relids,
+											&left_nappinfos);
+	right_appinfos = find_appinfos_by_relids(root, right_relids,
+											 &right_nappinfos);
+
+	sjinfo->min_lefthand = adjust_child_relids(sjinfo->min_lefthand,
+											   left_nappinfos, left_appinfos);
+	sjinfo->min_righthand = adjust_child_relids(sjinfo->min_righthand,
+												right_nappinfos,
+												right_appinfos);
+	sjinfo->syn_lefthand = adjust_child_relids(sjinfo->syn_lefthand,
+											   left_nappinfos, left_appinfos);
+	sjinfo->syn_righthand = adjust_child_relids(sjinfo->syn_righthand,
+												right_nappinfos,
+												right_appinfos);
+	sjinfo->semi_rhs_exprs = (List *) adjust_appendrel_attrs(root,
+															 (Node *) sjinfo->semi_rhs_exprs,
+															 right_nappinfos,
+															 right_appinfos);
+
+	pfree(left_appinfos);
+	pfree(right_appinfos);
+
+	return sjinfo;
+}
+
+/*
+ * find_appinfos_by_relids
+ * 		Find AppendRelInfo structures for all relations specified by relids.
+ *
+ * The AppendRelInfos are returned in an array, which can be pfree'd by the
+ * caller. *nappinfos is set to the number of entries in the array.
+ */
+AppendRelInfo **
+find_appinfos_by_relids(PlannerInfo *root, Relids relids, int *nappinfos)
+{
+	AppendRelInfo **appinfos;
+	int			cnt = 0;
+	int			i;
+
+	*nappinfos = bms_num_members(relids);
+	appinfos = (AppendRelInfo **) palloc(sizeof(AppendRelInfo *) * *nappinfos);
+
+	i = -1;
+	while ((i = bms_next_member(relids, i)) >= 0)
+	{
+		AppendRelInfo *appinfo = root->append_rel_array[i];
+
+		if (!appinfo)
+			elog(ERROR, "child rel %d not found in append_rel_array", i);
+
+		appinfos[cnt++] = appinfo;
+	}
+	return appinfos;
+}
diff --git a/src/backend/optimizer/util/inherit.c b/src/backend/optimizer/util/inherit.c
new file mode 100644
index 00000000000..350e6afe270
--- /dev/null
+++ b/src/backend/optimizer/util/inherit.c
@@ -0,0 +1,439 @@
+/*-------------------------------------------------------------------------
+ *
+ * inherit.c
+ *	  Routines to process child relations in inheritance trees
+ *
+ * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/optimizer/path/inherit.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/heapam.h"
+#include "catalog/partition.h"
+#include "catalog/pg_inherits.h"
+#include "miscadmin.h"
+#include "optimizer/appendinfo.h"
+#include "optimizer/inherit.h"
+#include "optimizer/planner.h"
+#include "optimizer/prep.h"
+#include "utils/rel.h"
+
+
+static void expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte,
+						 Index rti);
+static void expand_partitioned_rtentry(PlannerInfo *root,
+						   RangeTblEntry *parentrte,
+						   Index parentRTindex, Relation parentrel,
+						   PlanRowMark *top_parentrc, LOCKMODE lockmode,
+						   List **appinfos);
+static void expand_single_inheritance_child(PlannerInfo *root,
+								RangeTblEntry *parentrte,
+								Index parentRTindex, Relation parentrel,
+								PlanRowMark *top_parentrc, Relation childrel,
+								List **appinfos, RangeTblEntry **childrte_p,
+								Index *childRTindex_p);
+
+
+/*
+ * expand_inherited_tables
+ *		Expand each rangetable entry that represents an inheritance set
+ *		into an "append relation".  At the conclusion of this process,
+ *		the "inh" flag is set in all and only those RTEs that are append
+ *		relation parents.
+ */
+void
+expand_inherited_tables(PlannerInfo *root)
+{
+	Index		nrtes;
+	Index		rti;
+	ListCell   *rl;
+
+	/*
+	 * expand_inherited_rtentry may add RTEs to parse->rtable. The function is
+	 * expected to recursively handle any RTEs that it creates with inh=true.
+	 * So just scan as far as the original end of the rtable list.
+	 */
+	nrtes = list_length(root->parse->rtable);
+	rl = list_head(root->parse->rtable);
+	for (rti = 1; rti <= nrtes; rti++)
+	{
+		RangeTblEntry *rte = (RangeTblEntry *) lfirst(rl);
+
+		expand_inherited_rtentry(root, rte, rti);
+		rl = lnext(rl);
+	}
+}
+
+/*
+ * expand_inherited_rtentry
+ *		Check whether a rangetable entry represents an inheritance set.
+ *		If so, add entries for all the child tables to the query's
+ *		rangetable, and build AppendRelInfo nodes for all the child tables
+ *		and add them to root->append_rel_list.  If not, clear the entry's
+ *		"inh" flag to prevent later code from looking for AppendRelInfos.
+ *
+ * Note that the original RTE is considered to represent the whole
+ * inheritance set.  The first of the generated RTEs is an RTE for the same
+ * table, but with inh = false, to represent the parent table in its role
+ * as a simple member of the inheritance set.
+ *
+ * A childless table is never considered to be an inheritance set. For
+ * regular inheritance, a parent RTE must always have at least two associated
+ * AppendRelInfos: one corresponding to the parent table as a simple member of
+ * inheritance set and one or more corresponding to the actual children.
+ * Since a partitioned table is not scanned, it might have only one associated
+ * AppendRelInfo.
+ */
+static void
+expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
+{
+	Oid			parentOID;
+	PlanRowMark *oldrc;
+	Relation	oldrelation;
+	LOCKMODE	lockmode;
+	List	   *inhOIDs;
+	ListCell   *l;
+
+	/* Does RT entry allow inheritance? */
+	if (!rte->inh)
+		return;
+	/* Ignore any already-expanded UNION ALL nodes */
+	if (rte->rtekind != RTE_RELATION)
+	{
+		Assert(rte->rtekind == RTE_SUBQUERY);
+		return;
+	}
+	/* Fast path for common case of childless table */
+	parentOID = rte->relid;
+	if (!has_subclass(parentOID))
+	{
+		/* Clear flag before returning */
+		rte->inh = false;
+		return;
+	}
+
+	/*
+	 * The rewriter should already have obtained an appropriate lock on each
+	 * relation named in the query.  However, for each child relation we add
+	 * to the query, we must obtain an appropriate lock, because this will be
+	 * the first use of those relations in the parse/rewrite/plan pipeline.
+	 * Child rels should use the same lockmode as their parent.
+	 */
+	lockmode = rte->rellockmode;
+
+	/* Scan for all members of inheritance set, acquire needed locks */
+	inhOIDs = find_all_inheritors(parentOID, lockmode, NULL);
+
+	/*
+	 * Check that there's at least one descendant, else treat as no-child
+	 * case.  This could happen despite above has_subclass() check, if table
+	 * once had a child but no longer does.
+	 */
+	if (list_length(inhOIDs) < 2)
+	{
+		/* Clear flag before returning */
+		rte->inh = false;
+		return;
+	}
+
+	/*
+	 * If parent relation is selected FOR UPDATE/SHARE, we need to mark its
+	 * PlanRowMark as isParent = true, and generate a new PlanRowMark for each
+	 * child.
+	 */
+	oldrc = get_plan_rowmark(root->rowMarks, rti);
+	if (oldrc)
+		oldrc->isParent = true;
+
+	/*
+	 * Must open the parent relation to examine its tupdesc.  We need not lock
+	 * it; we assume the rewriter already did.
+	 */
+	oldrelation = heap_open(parentOID, NoLock);
+
+	/* Scan the inheritance set and expand it */
+	if (RelationGetPartitionDesc(oldrelation) != NULL)
+	{
+		Assert(rte->relkind == RELKIND_PARTITIONED_TABLE);
+
+		/*
+		 * If this table has partitions, recursively expand them in the order
+		 * in which they appear in the PartitionDesc.  While at it, also
+		 * extract the partition key columns of all the partitioned tables.
+		 */
+		expand_partitioned_rtentry(root, rte, rti, oldrelation, oldrc,
+								   lockmode, &root->append_rel_list);
+	}
+	else
+	{
+		List	   *appinfos = NIL;
+		RangeTblEntry *childrte;
+		Index		childRTindex;
+
+		/*
+		 * This table has no partitions.  Expand any plain inheritance
+		 * children in the order the OIDs were returned by
+		 * find_all_inheritors.
+		 */
+		foreach(l, inhOIDs)
+		{
+			Oid			childOID = lfirst_oid(l);
+			Relation	newrelation;
+
+			/* Open rel if needed; we already have required locks */
+			if (childOID != parentOID)
+				newrelation = heap_open(childOID, NoLock);
+			else
+				newrelation = oldrelation;
+
+			/*
+			 * It is possible that the parent table has children that are temp
+			 * tables of other backends.  We cannot safely access such tables
+			 * (because of buffering issues), and the best thing to do seems
+			 * to be to silently ignore them.
+			 */
+			if (childOID != parentOID && RELATION_IS_OTHER_TEMP(newrelation))
+			{
+				heap_close(newrelation, lockmode);
+				continue;
+			}
+
+			expand_single_inheritance_child(root, rte, rti, oldrelation, oldrc,
+											newrelation,
+											&appinfos, &childrte,
+											&childRTindex);
+
+			/* Close child relations, but keep locks */
+			if (childOID != parentOID)
+				heap_close(newrelation, NoLock);
+		}
+
+		/*
+		 * If all the children were temp tables, pretend it's a
+		 * non-inheritance situation; we don't need Append node in that case.
+		 * The duplicate RTE we added for the parent table is harmless, so we
+		 * don't bother to get rid of it; ditto for the useless PlanRowMark
+		 * node.
+		 */
+		if (list_length(appinfos) < 2)
+			rte->inh = false;
+		else
+			root->append_rel_list = list_concat(root->append_rel_list,
+												appinfos);
+
+	}
+
+	heap_close(oldrelation, NoLock);
+}
+
+/*
+ * expand_partitioned_rtentry
+ *		Recursively expand an RTE for a partitioned table.
+ */
+static void
+expand_partitioned_rtentry(PlannerInfo *root, RangeTblEntry *parentrte,
+						   Index parentRTindex, Relation parentrel,
+						   PlanRowMark *top_parentrc, LOCKMODE lockmode,
+						   List **appinfos)
+{
+	int			i;
+	RangeTblEntry *childrte;
+	Index		childRTindex;
+	PartitionDesc partdesc = RelationGetPartitionDesc(parentrel);
+
+	check_stack_depth();
+
+	/* A partitioned table should always have a partition descriptor. */
+	Assert(partdesc);
+
+	Assert(parentrte->inh);
+
+	/*
+	 * Note down whether any partition key cols are being updated. Though it's
+	 * the root partitioned table's updatedCols we are interested in, we
+	 * instead use parentrte to get the updatedCols. This is convenient
+	 * because parentrte already has the root partrel's updatedCols translated
+	 * to match the attribute ordering of parentrel.
+	 */
+	if (!root->partColsUpdated)
+		root->partColsUpdated =
+			has_partition_attrs(parentrel, parentrte->updatedCols, NULL);
+
+	/* First expand the partitioned table itself. */
+	expand_single_inheritance_child(root, parentrte, parentRTindex, parentrel,
+									top_parentrc, parentrel,
+									appinfos, &childrte, &childRTindex);
+
+	/*
+	 * If the partitioned table has no partitions, treat this as the
+	 * non-inheritance case.
+	 */
+	if (partdesc->nparts == 0)
+	{
+		parentrte->inh = false;
+		return;
+	}
+
+	for (i = 0; i < partdesc->nparts; i++)
+	{
+		Oid			childOID = partdesc->oids[i];
+		Relation	childrel;
+
+		/* Open rel; we already have required locks */
+		childrel = heap_open(childOID, NoLock);
+
+		/*
+		 * Temporary partitions belonging to other sessions should have been
+		 * disallowed at definition, but for paranoia's sake, let's double
+		 * check.
+		 */
+		if (RELATION_IS_OTHER_TEMP(childrel))
+			elog(ERROR, "temporary relation from another session found as partition");
+
+		expand_single_inheritance_child(root, parentrte, parentRTindex,
+										parentrel, top_parentrc, childrel,
+										appinfos, &childrte, &childRTindex);
+
+		/* If this child is itself partitioned, recurse */
+		if (childrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+			expand_partitioned_rtentry(root, childrte, childRTindex,
+									   childrel, top_parentrc, lockmode,
+									   appinfos);
+
+		/* Close child relation, but keep locks */
+		heap_close(childrel, NoLock);
+	}
+}
+
+/*
+ * expand_single_inheritance_child
+ *		Build a RangeTblEntry and an AppendRelInfo, if appropriate, plus
+ *		maybe a PlanRowMark.
+ *
+ * We now expand the partition hierarchy level by level, creating a
+ * corresponding hierarchy of AppendRelInfos and RelOptInfos, where each
+ * partitioned descendant acts as a parent of its immediate partitions.
+ * (This is a difference from what older versions of PostgreSQL did and what
+ * is still done in the case of table inheritance for unpartitioned tables,
+ * where the hierarchy is flattened during RTE expansion.)
+ *
+ * PlanRowMarks still carry the top-parent's RTI, and the top-parent's
+ * allMarkTypes field still accumulates values from all descendents.
+ *
+ * "parentrte" and "parentRTindex" are immediate parent's RTE and
+ * RTI. "top_parentrc" is top parent's PlanRowMark.
+ *
+ * The child RangeTblEntry and its RTI are returned in "childrte_p" and
+ * "childRTindex_p" resp.
+ */
+static void
+expand_single_inheritance_child(PlannerInfo *root, RangeTblEntry *parentrte,
+								Index parentRTindex, Relation parentrel,
+								PlanRowMark *top_parentrc, Relation childrel,
+								List **appinfos, RangeTblEntry **childrte_p,
+								Index *childRTindex_p)
+{
+	Query	   *parse = root->parse;
+	Oid			parentOID = RelationGetRelid(parentrel);
+	Oid			childOID = RelationGetRelid(childrel);
+	RangeTblEntry *childrte;
+	Index		childRTindex;
+	AppendRelInfo *appinfo;
+
+	/*
+	 * Build an RTE for the child, and attach to query's rangetable list. We
+	 * copy most fields of the parent's RTE, but replace relation OID and
+	 * relkind, and set inh = false.  Also, set requiredPerms to zero since
+	 * all required permissions checks are done on the original RTE. Likewise,
+	 * set the child's securityQuals to empty, because we only want to apply
+	 * the parent's RLS conditions regardless of what RLS properties
+	 * individual children may have.  (This is an intentional choice to make
+	 * inherited RLS work like regular permissions checks.) The parent
+	 * securityQuals will be propagated to children along with other base
+	 * restriction clauses, so we don't need to do it here.
+	 */
+	childrte = copyObject(parentrte);
+	*childrte_p = childrte;
+	childrte->relid = childOID;
+	childrte->relkind = childrel->rd_rel->relkind;
+	/* A partitioned child will need to be expanded further. */
+	if (childOID != parentOID &&
+		childrte->relkind == RELKIND_PARTITIONED_TABLE)
+		childrte->inh = true;
+	else
+		childrte->inh = false;
+	childrte->requiredPerms = 0;
+	childrte->securityQuals = NIL;
+	parse->rtable = lappend(parse->rtable, childrte);
+	childRTindex = list_length(parse->rtable);
+	*childRTindex_p = childRTindex;
+
+	/*
+	 * We need an AppendRelInfo if paths will be built for the child RTE. If
+	 * childrte->inh is true, then we'll always need to generate append paths
+	 * for it.  If childrte->inh is false, we must scan it if it's not a
+	 * partitioned table; but if it is a partitioned table, then it never has
+	 * any data of its own and need not be scanned.
+	 */
+	if (childrte->relkind != RELKIND_PARTITIONED_TABLE || childrte->inh)
+	{
+		appinfo = make_append_rel_info(parentrel, childrel,
+									   parentRTindex, childRTindex);
+		*appinfos = lappend(*appinfos, appinfo);
+
+		/*
+		 * Translate the column permissions bitmaps to the child's attnums (we
+		 * have to build the translated_vars list before we can do this). But
+		 * if this is the parent table, leave copyObject's result alone.
+		 *
+		 * Note: we need to do this even though the executor won't run any
+		 * permissions checks on the child RTE.  The insertedCols/updatedCols
+		 * bitmaps may be examined for trigger-firing purposes.
+		 */
+		if (childOID != parentOID)
+		{
+			childrte->selectedCols = translate_col_privs(parentrte->selectedCols,
+														 appinfo->translated_vars);
+			childrte->insertedCols = translate_col_privs(parentrte->insertedCols,
+														 appinfo->translated_vars);
+			childrte->updatedCols = translate_col_privs(parentrte->updatedCols,
+														appinfo->translated_vars);
+		}
+	}
+
+	/*
+	 * Build a PlanRowMark if parent is marked FOR UPDATE/SHARE.
+	 */
+	if (top_parentrc)
+	{
+		PlanRowMark *childrc = makeNode(PlanRowMark);
+
+		childrc->rti = childRTindex;
+		childrc->prti = top_parentrc->rti;
+		childrc->rowmarkId = top_parentrc->rowmarkId;
+		/* Reselect rowmark type, because relkind might not match parent */
+		childrc->markType = select_rowmark_type(childrte,
+												top_parentrc->strength);
+		childrc->allMarkTypes = (1 << childrc->markType);
+		childrc->strength = top_parentrc->strength;
+		childrc->waitPolicy = top_parentrc->waitPolicy;
+
+		/*
+		 * We mark RowMarks for partitioned child tables as parent RowMarks so
+		 * that the executor ignores them (except their existence means that
+		 * the child tables be locked using appropriate mode).
+		 */
+		childrc->isParent = (childrte->relkind == RELKIND_PARTITIONED_TABLE);
+
+		/* Include child's rowmark type in top parent's allMarkTypes */
+		top_parentrc->allMarkTypes |= childrc->allMarkTypes;
+
+		root->rowMarks = lappend(root->rowMarks, childrc);
+	}
+}
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 5921e893c12..b2637d0e89a 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -20,6 +20,7 @@
 #include "foreign/fdwapi.h"
 #include "nodes/extensible.h"
 #include "nodes/nodeFuncs.h"
+#include "optimizer/appendinfo.h"
 #include "optimizer/clauses.h"
 #include "optimizer/cost.h"
 #include "optimizer/pathnode.h"
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index 111b42d6548..fe83ec45192 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -17,6 +17,7 @@
 #include <limits.h>
 
 #include "miscadmin.h"
+#include "optimizer/appendinfo.h"
 #include "optimizer/clauses.h"
 #include "optimizer/cost.h"
 #include "optimizer/pathnode.h"