Fix handling of expressions and predicates in REINDEX CONCURRENTLY

When copying the definition of an index rebuilt concurrently for the new
entry, the index information was taken directly from the old index using
the relation cache.  In this case, predicates and expressions have
some post-processing to prepare things for the planner, which loses some
information including the collations added in any of them.

This inconsistency can cause issues when attempting for example a table
rewrite, and makes the new indexes rebuilt concurrently inconsistent
with the old entries.

In order to fix the problem, fetch expressions and predicates directly
from the catalog of the old entry, and fill in IndexInfo for the new
index with that.  This makes the process more consistent with
DefineIndex(), and the code is refactored with the addition of a routine
to create an IndexInfo node.

Reported-by: Manuel Rigger
Author: Michael Paquier
Discussion: https://postgr.es/m/CA+u7OA5Hp0ra235F3czPom_FyAd-3+XwSJmX95r1+sRPOJc9VQ@mail.gmail.com
Backpatch-through: 12

src/backend/catalog/index.c

@@ -1197,7 +1197,8 @@ Oid
 index_concurrently_create_copy(Relation heapRelation, Oid oldIndexId, const char *newName)
 {
 	Relation	indexRelation;
-	IndexInfo  *indexInfo;
+	IndexInfo  *oldInfo,
+			   *newInfo;
 	Oid			newIndexId = InvalidOid;
 	HeapTuple	indexTuple,
 				classTuple;
@@ -1208,11 +1209,22 @@ index_concurrently_create_copy(Relation heapRelation, Oid oldIndexId, const char
 	int2vector *indcoloptions;
 	bool		isnull;
 	List	   *indexColNames = NIL;
+	List	   *indexExprs = NIL;
+	List	   *indexPreds = NIL;
 
 	indexRelation = index_open(oldIndexId, RowExclusiveLock);
 
-	/* New index uses the same index information as old index */
-	indexInfo = BuildIndexInfo(indexRelation);
+	/* The new index needs some information from the old index */
+	oldInfo = BuildIndexInfo(indexRelation);
+
+	/*
+	 * Concurrent build of an index with exclusion constraints is not
+	 * supported.
+	 */
+	if (oldInfo->ii_ExclusionOps != NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("concurrent index creation for exclusion constraints is not supported")));
 
 	/* Get the array of class and column options IDs from index info */
 	indexTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(oldIndexId));
@@ -1236,14 +1248,64 @@ index_concurrently_create_copy(Relation heapRelation, Oid oldIndexId, const char
 								  Anum_pg_class_reloptions, &isnull);
 
 	/*
-	 * Extract the list of column names to be used for the index creation.
+	 * Fetch the list of expressions and predicates directly from the
+	 * catalogs.  This cannot rely on the information from IndexInfo of the
+	 * old index as these have been flattened for the planner.
 	 */
-	for (int i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
+	if (oldInfo->ii_Expressions != NIL)
+	{
+		Datum		exprDatum;
+		char	   *exprString;
+
+		exprDatum = SysCacheGetAttr(INDEXRELID, indexTuple,
+									Anum_pg_index_indexprs, &isnull);
+		Assert(!isnull);
+		exprString = TextDatumGetCString(exprDatum);
+		indexExprs = (List *) stringToNode(exprString);
+		pfree(exprString);
+	}
+	if (oldInfo->ii_Predicate != NIL)
+	{
+		Datum		predDatum;
+		char	   *predString;
+
+		predDatum = SysCacheGetAttr(INDEXRELID, indexTuple,
+									Anum_pg_index_indpred, &isnull);
+		Assert(!isnull);
+		predString = TextDatumGetCString(predDatum);
+		indexPreds = (List *) stringToNode(predString);
+
+		/* Also convert to implicit-AND format */
+		indexPreds = make_ands_implicit((Expr *) indexPreds);
+		pfree(predString);
+	}
+
+	/*
+	 * Build the index information for the new index.  Note that rebuild of
+	 * indexes with exclusion constraints is not supported, hence there is no
+	 * need to fill all the ii_Exclusion* fields.
+	 */
+	newInfo = makeIndexInfo(oldInfo->ii_NumIndexAttrs,
+							oldInfo->ii_NumIndexKeyAttrs,
+							oldInfo->ii_Am,
+							indexExprs,
+							indexPreds,
+							oldInfo->ii_Unique,
+							false,	/* not ready for inserts */
+							true);
+
+	/*
+	 * Extract the list of column names and the column numbers for the new
+	 * index information.  All this information will be used for the index
+	 * creation.
+	 */
+	for (int i = 0; i < oldInfo->ii_NumIndexAttrs; i++)
 	{
 		TupleDesc	indexTupDesc = RelationGetDescr(indexRelation);
 		Form_pg_attribute att = TupleDescAttr(indexTupDesc, i);
 
 		indexColNames = lappend(indexColNames, NameStr(att->attname));
+		newInfo->ii_IndexAttrNumbers[i] = oldInfo->ii_IndexAttrNumbers[i];
 	}
 
 	/*
@@ -1259,7 +1321,7 @@ index_concurrently_create_copy(Relation heapRelation, Oid oldIndexId, const char
 							  InvalidOid,	/* parentIndexRelid */
 							  InvalidOid,	/* parentConstraintId */
 							  InvalidOid,	/* relFileNode */
-							  indexInfo,
+							  newInfo,
 							  indexColNames,
 							  indexRelation->rd_rel->relam,
 							  indexRelation->rd_rel->reltablespace,

src/backend/commands/indexcmds.c

@@ -202,18 +202,8 @@ CheckIndexCompatible(Oid oldId,
 	 * contains only key attributes, thus we're filling ii_NumIndexAttrs and
 	 * ii_NumIndexKeyAttrs with same value.
 	 */
-	indexInfo = makeNode(IndexInfo);
-	indexInfo->ii_NumIndexAttrs = numberOfAttributes;
-	indexInfo->ii_NumIndexKeyAttrs = numberOfAttributes;
-	indexInfo->ii_Expressions = NIL;
-	indexInfo->ii_ExpressionsState = NIL;
-	indexInfo->ii_PredicateState = NULL;
-	indexInfo->ii_ExclusionOps = NULL;
-	indexInfo->ii_ExclusionProcs = NULL;
-	indexInfo->ii_ExclusionStrats = NULL;
-	indexInfo->ii_Am = accessMethodId;
-	indexInfo->ii_AmCache = NULL;
-	indexInfo->ii_Context = CurrentMemoryContext;
+	indexInfo = makeIndexInfo(numberOfAttributes, numberOfAttributes,
+							  accessMethodId, NIL, NIL, false, false, false);
 	typeObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));
 	collationObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));
 	classObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));
@@ -780,27 +770,17 @@ DefineIndex(Oid relationId,
 
 	/*
 	 * Prepare arguments for index_create, primarily an IndexInfo structure.
-	 * Note that ii_Predicate must be in implicit-AND format.
-	 */
-	indexInfo = makeNode(IndexInfo);
-	indexInfo->ii_NumIndexAttrs = numberOfAttributes;
-	indexInfo->ii_NumIndexKeyAttrs = numberOfKeyAttributes;
-	indexInfo->ii_Expressions = NIL;	/* for now */
-	indexInfo->ii_ExpressionsState = NIL;
-	indexInfo->ii_Predicate = make_ands_implicit((Expr *) stmt->whereClause);
-	indexInfo->ii_PredicateState = NULL;
-	indexInfo->ii_ExclusionOps = NULL;
-	indexInfo->ii_ExclusionProcs = NULL;
-	indexInfo->ii_ExclusionStrats = NULL;
-	indexInfo->ii_Unique = stmt->unique;
-	/* In a concurrent build, mark it not-ready-for-inserts */
-	indexInfo->ii_ReadyForInserts = !stmt->concurrent;
-	indexInfo->ii_Concurrent = stmt->concurrent;
-	indexInfo->ii_BrokenHotChain = false;
-	indexInfo->ii_ParallelWorkers = 0;
-	indexInfo->ii_Am = accessMethodId;
-	indexInfo->ii_AmCache = NULL;
-	indexInfo->ii_Context = CurrentMemoryContext;
+	 * Note that predicates must be in implicit-AND format.  In a concurrent
+	 * build, mark it not-ready-for-inserts.
+	 */
+	indexInfo = makeIndexInfo(numberOfAttributes,
+							  numberOfKeyAttributes,
+							  accessMethodId,
+							  NIL,	/* expressions, NIL for now */
+							  make_ands_implicit((Expr *) stmt->whereClause),
+							  stmt->unique,
+							  !stmt->concurrent,
+							  stmt->concurrent);
 
 	typeObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));
 	collationObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));

src/backend/nodes/makefuncs.c

 /*-------------------------------------------------------------------------
  *
  * makefuncs.c
- *	  creator functions for primitive nodes. The functions here are for
- *	  the most frequently created nodes.
+ *	  creator functions for various nodes. The functions here are for the
+ *	  most frequently created nodes.
  *
  * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
@@ -733,6 +733,54 @@ make_ands_implicit(Expr *clause)
 		return list_make1(clause);
 }
 
+/*
+ * makeIndexInfo
+ *	  create an IndexInfo node
+ */
+IndexInfo *
+makeIndexInfo(int numattrs, int numkeyattrs, Oid amoid, List *expressions,
+			  List *predicates, bool unique, bool isready, bool concurrent)
+{
+	IndexInfo  *n = makeNode(IndexInfo);
+
+	n->ii_NumIndexAttrs = numattrs;
+	n->ii_NumIndexKeyAttrs = numkeyattrs;
+	Assert(n->ii_NumIndexKeyAttrs != 0);
+	Assert(n->ii_NumIndexKeyAttrs <= n->ii_NumIndexAttrs);
+	n->ii_Unique = unique;
+	n->ii_ReadyForInserts = isready;
+	n->ii_Concurrent = concurrent;
+
+	/* expressions */
+	n->ii_Expressions = expressions;
+	n->ii_ExpressionsState = NIL;
+
+	/* predicates  */
+	n->ii_Predicate = predicates;
+	n->ii_PredicateState = NULL;
+
+	/* exclusion constraints */
+	n->ii_ExclusionOps = NULL;
+	n->ii_ExclusionProcs = NULL;
+	n->ii_ExclusionStrats = NULL;
+
+	/* speculative inserts */
+	n->ii_UniqueOps = NULL;
+	n->ii_UniqueProcs = NULL;
+	n->ii_UniqueStrats = NULL;
+
+	/* initialize index-build state to default */
+	n->ii_BrokenHotChain = false;
+	n->ii_ParallelWorkers = 0;
+
+	/* set up for possible use by index AM */
+	n->ii_Am = amoid;
+	n->ii_AmCache = NULL;
+	n->ii_Context = CurrentMemoryContext;
+
+	return n;
+}
+
 /*
  * makeGroupingSet
  *

src/include/nodes/makefuncs.h

 /*-------------------------------------------------------------------------
  *
  * makefuncs.h
- *	  prototypes for the creator functions (for primitive nodes)
+ *	  prototypes for the creator functions of various nodes
  *
  *
  * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
@@ -14,6 +14,7 @@
 #ifndef MAKEFUNC_H
 #define MAKEFUNC_H
 
+#include "nodes/execnodes.h"
 #include "nodes/parsenodes.h"
 
 
@@ -92,6 +93,10 @@ extern Node *make_and_qual(Node *qual1, Node *qual2);
 extern Expr *make_ands_explicit(List *andclauses);
 extern List *make_ands_implicit(Expr *clause);
 
+extern IndexInfo *makeIndexInfo(int numattrs, int numkeyattrs, Oid amoid,
+								List *expressions, List *predicates,
+								bool unique, bool isready, bool concurrent);
+
 extern DefElem *makeDefElem(char *name, Node *arg, int location);
 extern DefElem *makeDefElemExtended(char *nameSpace, char *name, Node *arg,
 									DefElemAction defaction, int location);

src/test/regress/expected/create_index.out

@@ -2170,6 +2170,78 @@ Indexes:
     "concur_reindex_ind5" UNIQUE, btree (c1)
 
 DROP TABLE concur_reindex_tab4;
+-- Check handling of indexes with expressions and predicates.  The
+-- definitions of the rebuilt indexes should match the original
+-- definitions.
+CREATE TABLE concur_exprs_tab (c1 int , c2 boolean);
+INSERT INTO concur_exprs_tab (c1, c2) VALUES (1369652450, FALSE),
+  (414515746, TRUE),
+  (897778963, FALSE);
+CREATE UNIQUE INDEX concur_exprs_index_expr
+  ON concur_exprs_tab ((c1::text COLLATE "C"));
+CREATE UNIQUE INDEX concur_exprs_index_pred ON concur_exprs_tab (c1)
+  WHERE (c1::text > 500000000::text COLLATE "C");
+CREATE UNIQUE INDEX concur_exprs_index_pred_2
+  ON concur_exprs_tab ((1 / c1))
+  WHERE ('-H') >= (c2::TEXT) COLLATE "C";
+SELECT pg_get_indexdef('concur_exprs_index_expr'::regclass);
+                                                pg_get_indexdef                                                
+---------------------------------------------------------------------------------------------------------------
+ CREATE UNIQUE INDEX concur_exprs_index_expr ON public.concur_exprs_tab USING btree (((c1)::text) COLLATE "C")
+(1 row)
+
+SELECT pg_get_indexdef('concur_exprs_index_pred'::regclass);
+                                                               pg_get_indexdef                                                                
+----------------------------------------------------------------------------------------------------------------------------------------------
+ CREATE UNIQUE INDEX concur_exprs_index_pred ON public.concur_exprs_tab USING btree (c1) WHERE ((c1)::text > ((500000000)::text COLLATE "C"))
+(1 row)
+
+SELECT pg_get_indexdef('concur_exprs_index_pred_2'::regclass);
+                                                                 pg_get_indexdef                                                                  
+--------------------------------------------------------------------------------------------------------------------------------------------------
+ CREATE UNIQUE INDEX concur_exprs_index_pred_2 ON public.concur_exprs_tab USING btree (((1 / c1))) WHERE ('-H'::text >= ((c2)::text COLLATE "C"))
+(1 row)
+
+REINDEX TABLE CONCURRENTLY concur_exprs_tab;
+SELECT pg_get_indexdef('concur_exprs_index_expr'::regclass);
+                                                pg_get_indexdef                                                
+---------------------------------------------------------------------------------------------------------------
+ CREATE UNIQUE INDEX concur_exprs_index_expr ON public.concur_exprs_tab USING btree (((c1)::text) COLLATE "C")
+(1 row)
+
+SELECT pg_get_indexdef('concur_exprs_index_pred'::regclass);
+                                                               pg_get_indexdef                                                                
+----------------------------------------------------------------------------------------------------------------------------------------------
+ CREATE UNIQUE INDEX concur_exprs_index_pred ON public.concur_exprs_tab USING btree (c1) WHERE ((c1)::text > ((500000000)::text COLLATE "C"))
+(1 row)
+
+SELECT pg_get_indexdef('concur_exprs_index_pred_2'::regclass);
+                                                                 pg_get_indexdef                                                                  
+--------------------------------------------------------------------------------------------------------------------------------------------------
+ CREATE UNIQUE INDEX concur_exprs_index_pred_2 ON public.concur_exprs_tab USING btree (((1 / c1))) WHERE ('-H'::text >= ((c2)::text COLLATE "C"))
+(1 row)
+
+-- ALTER TABLE recreates the indexes, which should keep their collations.
+ALTER TABLE concur_exprs_tab ALTER c2 TYPE TEXT;
+SELECT pg_get_indexdef('concur_exprs_index_expr'::regclass);
+                                                pg_get_indexdef                                                
+---------------------------------------------------------------------------------------------------------------
+ CREATE UNIQUE INDEX concur_exprs_index_expr ON public.concur_exprs_tab USING btree (((c1)::text) COLLATE "C")
+(1 row)
+
+SELECT pg_get_indexdef('concur_exprs_index_pred'::regclass);
+                                                               pg_get_indexdef                                                                
+----------------------------------------------------------------------------------------------------------------------------------------------
+ CREATE UNIQUE INDEX concur_exprs_index_pred ON public.concur_exprs_tab USING btree (c1) WHERE ((c1)::text > ((500000000)::text COLLATE "C"))
+(1 row)
+
+SELECT pg_get_indexdef('concur_exprs_index_pred_2'::regclass);
+                                                             pg_get_indexdef                                                              
+------------------------------------------------------------------------------------------------------------------------------------------
+ CREATE UNIQUE INDEX concur_exprs_index_pred_2 ON public.concur_exprs_tab USING btree (((1 / c1))) WHERE ('-H'::text >= (c2 COLLATE "C"))
+(1 row)
+
+DROP TABLE concur_exprs_tab;
 --
 -- REINDEX SCHEMA
 --

src/test/regress/sql/create_index.sql

@@ -872,6 +872,34 @@ REINDEX INDEX CONCURRENTLY concur_reindex_ind5;
 \d concur_reindex_tab4
 DROP TABLE concur_reindex_tab4;
 
+-- Check handling of indexes with expressions and predicates.  The
+-- definitions of the rebuilt indexes should match the original
+-- definitions.
+CREATE TABLE concur_exprs_tab (c1 int , c2 boolean);
+INSERT INTO concur_exprs_tab (c1, c2) VALUES (1369652450, FALSE),
+  (414515746, TRUE),
+  (897778963, FALSE);
+CREATE UNIQUE INDEX concur_exprs_index_expr
+  ON concur_exprs_tab ((c1::text COLLATE "C"));
+CREATE UNIQUE INDEX concur_exprs_index_pred ON concur_exprs_tab (c1)
+  WHERE (c1::text > 500000000::text COLLATE "C");
+CREATE UNIQUE INDEX concur_exprs_index_pred_2
+  ON concur_exprs_tab ((1 / c1))
+  WHERE ('-H') >= (c2::TEXT) COLLATE "C";
+SELECT pg_get_indexdef('concur_exprs_index_expr'::regclass);
+SELECT pg_get_indexdef('concur_exprs_index_pred'::regclass);
+SELECT pg_get_indexdef('concur_exprs_index_pred_2'::regclass);
+REINDEX TABLE CONCURRENTLY concur_exprs_tab;
+SELECT pg_get_indexdef('concur_exprs_index_expr'::regclass);
+SELECT pg_get_indexdef('concur_exprs_index_pred'::regclass);
+SELECT pg_get_indexdef('concur_exprs_index_pred_2'::regclass);
+-- ALTER TABLE recreates the indexes, which should keep their collations.
+ALTER TABLE concur_exprs_tab ALTER c2 TYPE TEXT;
+SELECT pg_get_indexdef('concur_exprs_index_expr'::regclass);
+SELECT pg_get_indexdef('concur_exprs_index_pred'::regclass);
+SELECT pg_get_indexdef('concur_exprs_index_pred_2'::regclass);
+DROP TABLE concur_exprs_tab;
+
 --
 -- REINDEX SCHEMA
 --