From 4178849736c81ec17bbfb2628ec0ef7bad94962d Mon Sep 17 00:00:00 2001
From: drh <>
Date: Wed, 2 Aug 2023 00:09:15 +0000
Subject: [PATCH 1/4] When a query is inside an AS MATERIALIZED CTE, do not
 attempt the omit-ORDER-BY optimization.  If the developer specifies
 MATERIALIZED, that means he wants the sort to actually happen.

FossilOrigin-Name: aa769ee7477171f26a091cadff98aa4f48da7752ade20b405a95c4525456f62e
---
 manifest      | 15 +++++++++------
 manifest.uuid |  2 +-
 src/select.c  |  2 ++
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/manifest b/manifest
index 6111b63076..d796df9ebc 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Avoid\sASAN\swarnings\swhen\sconverting\sover-sized\slong\sdouble\svalues\sinto\sdouble.
-D 2023-08-01T19:10:30.602
+C When\sa\squery\sis\sinside\san\sAS\sMATERIALIZED\sCTE,\sdo\snot\sattempt\sthe\nomit-ORDER-BY\soptimization.\s\sIf\sthe\sdeveloper\sspecifies\sMATERIALIZED,\nthat\smeans\she\swants\sthe\ssort\sto\sactually\shappen.
+D 2023-08-02T00:09:15.460
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -643,7 +643,7 @@ F src/printf.c e3ba080e2f409f9bfcc8d34724e6fc160e9c718dc92d0548f6b71b8b6f860ce2
 F src/random.c 606b00941a1d7dd09c381d3279a058d771f406c5213c9932bbd93d5587be4b9c
 F src/resolve.c 37953a5f36c60bea413c3c04efcd433b6177009f508ef2ace0494728912fe2e9
 F src/rowset.c 8432130e6c344b3401a8874c3cb49fefe6873fec593294de077afea2dce5ec97
-F src/select.c 3328b8c758016b400a4fea053ab1f5927929083a49d0c3921802ce99eea73cde
+F src/select.c 0ea15e379b2eb09d1a803499438b957c59af7264996903ec9b9a4aeb0402293b
 F src/shell.c.in 694aaf751f00610381533d4a31c83d142cfc83ef91ef65e2aa6912ace7c39b40
 F src/sqlite.h.in 7b07a33d2af82ee974aa91e6294abce0282b2f4c5934b291d2fff961810dd867
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
@@ -2049,8 +2049,11 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P ef7c121049f77200ecc4da260a90776264af0e84122d0133b4986959aedc653a
-R c483adf60f57a6109b239d1712365b26
+P e989a37ff9d5b52e0090d59be077ad2260c8df5d4c2c2d8088b1160de64dffd4
+R 85471d4376eb004f17191da107252ebb
+T *branch * materialize-order-by
+T *sym-materialize-order-by *
+T -sym-trunk *
 U drh
-Z 2befc2bb54d1f8208d12f5236dacb8de
+Z 34b88ebfe26392ded7967d5b47a75b8d
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index feb55dd783..1b72fd535b 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-e989a37ff9d5b52e0090d59be077ad2260c8df5d4c2c2d8088b1160de64dffd4
\ No newline at end of file
+aa769ee7477171f26a091cadff98aa4f48da7752ade20b405a95c4525456f62e
\ No newline at end of file
diff --git a/src/select.c b/src/select.c
index 098b745849..7f73b19287 100644
--- a/src/select.c
+++ b/src/select.c
@@ -7314,12 +7314,14 @@ int sqlite3Select(
     **            (a)  The outer query has a different ORDER BY clause
     **            (b)  The subquery is part of a join
     **          See forum post 062d576715d277c8
+    **    (6)   The subquery is really a MATERIALIZED CTE
     */
     if( pSub->pOrderBy!=0
      && (p->pOrderBy!=0 || pTabList->nSrc>1)      /* Condition (5) */
      && pSub->pLimit==0                           /* Condition (1) */
      && (pSub->selFlags & SF_OrderByReqd)==0      /* Condition (2) */
      && (p->selFlags & SF_OrderByReqd)==0         /* Condition (3) and (4) */
+     && (pItem->fg.isCte==0 || pItem->u2.pCteUse->eM10d!=M10d_Yes) /* (6) */
      && OptimizationEnabled(db, SQLITE_OmitOrderBy)
     ){
       TREETRACE(0x800,pParse,p,

From 5e82c06cf89a5d3d57f8cbb206a7142c9c4c4a0c Mon Sep 17 00:00:00 2001
From: drh <>
Date: Wed, 2 Aug 2023 11:06:27 +0000
Subject: [PATCH 2/4] Never flatten a CTE that is labeled MATERIALIZED.  This
 is really something of a bug fix because the documentation says that a
 MATERIALIZED CTE is an optimization barrier.

FossilOrigin-Name: b7ef9796f548ce43e06673f86bbec68157aae5e4ee8451e1d87ee5f70af1bb27
---
 manifest      | 15 ++++++---------
 manifest.uuid |  2 +-
 src/select.c  | 14 +++++++++++++-
 3 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/manifest b/manifest
index d796df9ebc..228342f6be 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C When\sa\squery\sis\sinside\san\sAS\sMATERIALIZED\sCTE,\sdo\snot\sattempt\sthe\nomit-ORDER-BY\soptimization.\s\sIf\sthe\sdeveloper\sspecifies\sMATERIALIZED,\nthat\smeans\she\swants\sthe\ssort\sto\sactually\shappen.
-D 2023-08-02T00:09:15.460
+C Never\sflatten\sa\sCTE\sthat\sis\slabeled\sMATERIALIZED.\s\sThis\sis\sreally\ssomething\nof\sa\sbug\sfix\sbecause\sthe\sdocumentation\ssays\sthat\sa\sMATERIALIZED\sCTE\sis\san\noptimization\sbarrier.
+D 2023-08-02T11:06:27.030
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -643,7 +643,7 @@ F src/printf.c e3ba080e2f409f9bfcc8d34724e6fc160e9c718dc92d0548f6b71b8b6f860ce2
 F src/random.c 606b00941a1d7dd09c381d3279a058d771f406c5213c9932bbd93d5587be4b9c
 F src/resolve.c 37953a5f36c60bea413c3c04efcd433b6177009f508ef2ace0494728912fe2e9
 F src/rowset.c 8432130e6c344b3401a8874c3cb49fefe6873fec593294de077afea2dce5ec97
-F src/select.c 0ea15e379b2eb09d1a803499438b957c59af7264996903ec9b9a4aeb0402293b
+F src/select.c 10ff496138ffa5bf5c3d9c7808b7558cb9b398d12062c464037167748075a13f
 F src/shell.c.in 694aaf751f00610381533d4a31c83d142cfc83ef91ef65e2aa6912ace7c39b40
 F src/sqlite.h.in 7b07a33d2af82ee974aa91e6294abce0282b2f4c5934b291d2fff961810dd867
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
@@ -2049,11 +2049,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P e989a37ff9d5b52e0090d59be077ad2260c8df5d4c2c2d8088b1160de64dffd4
-R 85471d4376eb004f17191da107252ebb
-T *branch * materialize-order-by
-T *sym-materialize-order-by *
-T -sym-trunk *
+P aa769ee7477171f26a091cadff98aa4f48da7752ade20b405a95c4525456f62e
+R 5d3359f6c6d5e2c6f797651e2c52272a
 U drh
-Z 34b88ebfe26392ded7967d5b47a75b8d
+Z d3d190ae3372df83f9be614d98609288
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 1b72fd535b..1ef995c32e 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-aa769ee7477171f26a091cadff98aa4f48da7752ade20b405a95c4525456f62e
\ No newline at end of file
+b7ef9796f548ce43e06673f86bbec68157aae5e4ee8451e1d87ee5f70af1bb27
\ No newline at end of file
diff --git a/src/select.c b/src/select.c
index 7f73b19287..7a3ba4a6fa 100644
--- a/src/select.c
+++ b/src/select.c
@@ -7314,7 +7314,14 @@ int sqlite3Select(
     **            (a)  The outer query has a different ORDER BY clause
     **            (b)  The subquery is part of a join
     **          See forum post 062d576715d277c8
+    **
+    ** The above cases might get an incorrect result if ORDER BY is omitted.
+    ** The following constraints are not required for correct answers, but are
+    ** included in order to give developers more control over when a sort
+    ** occurs:
+    **
     **    (6)   The subquery is really a MATERIALIZED CTE
+    **    (7)   The OmitOrderBy optimization is disabled
     */
     if( pSub->pOrderBy!=0
      && (p->pOrderBy!=0 || pTabList->nSrc>1)      /* Condition (5) */
@@ -7322,7 +7329,7 @@ int sqlite3Select(
      && (pSub->selFlags & SF_OrderByReqd)==0      /* Condition (2) */
      && (p->selFlags & SF_OrderByReqd)==0         /* Condition (3) and (4) */
      && (pItem->fg.isCte==0 || pItem->u2.pCteUse->eM10d!=M10d_Yes) /* (6) */
-     && OptimizationEnabled(db, SQLITE_OmitOrderBy)
+     && OptimizationEnabled(db, SQLITE_OmitOrderBy)                /* (7) */
     ){
       TREETRACE(0x800,pParse,p,
                 ("omit superfluous ORDER BY on %r FROM-clause subquery\n",i+1));
@@ -7359,6 +7366,11 @@ int sqlite3Select(
       continue;
     }
 
+    /* Do not flatten a MATERIALIZED CTE */
+    if( pItem->fg.isCte && pItem->u2.pCteUse->eM10d==M10d_Yes ){
+      continue;
+    }
+
     if( flattenSubquery(pParse, p, i, isAgg) ){
       if( pParse->nErr ) goto select_end;
       /* This subquery can be absorbed into its parent. */

From aa250db66aed4ed8f969d61f05bc374aa8c2c2e6 Mon Sep 17 00:00:00 2001
From: drh <>
Date: Wed, 2 Aug 2023 12:39:56 +0000
Subject: [PATCH 3/4] Simplify the select.c logic that enforces the
 optimization fence around a MATERIALIZED common table expression.  Do not
 allow the reverse_unordered_selects setting to affect a fenced CTE that
 itself has an ORDER BY clause.

FossilOrigin-Name: 165b9bda243777ae7fb6f51ee7ad58771c581b82ef9a70268eb9764e9e6eba6f
---
 manifest      | 14 +++++++-------
 manifest.uuid |  2 +-
 src/select.c  | 24 ++++++++++--------------
 src/where.c   | 21 ++++++++++++++++++++-
 4 files changed, 38 insertions(+), 23 deletions(-)

diff --git a/manifest b/manifest
index 228342f6be..043e5c2130 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Never\sflatten\sa\sCTE\sthat\sis\slabeled\sMATERIALIZED.\s\sThis\sis\sreally\ssomething\nof\sa\sbug\sfix\sbecause\sthe\sdocumentation\ssays\sthat\sa\sMATERIALIZED\sCTE\sis\san\noptimization\sbarrier.
-D 2023-08-02T11:06:27.030
+C Simplify\sthe\sselect.c\slogic\sthat\senforces\sthe\soptimization\sfence\saround\na\sMATERIALIZED\scommon\stable\sexpression.\s\sDo\snot\sallow\sthe\nreverse_unordered_selects\ssetting\sto\saffect\sa\sfenced\sCTE\sthat\sitself\shas\nan\sORDER\sBY\sclause.
+D 2023-08-02T12:39:56.675
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -643,7 +643,7 @@ F src/printf.c e3ba080e2f409f9bfcc8d34724e6fc160e9c718dc92d0548f6b71b8b6f860ce2
 F src/random.c 606b00941a1d7dd09c381d3279a058d771f406c5213c9932bbd93d5587be4b9c
 F src/resolve.c 37953a5f36c60bea413c3c04efcd433b6177009f508ef2ace0494728912fe2e9
 F src/rowset.c 8432130e6c344b3401a8874c3cb49fefe6873fec593294de077afea2dce5ec97
-F src/select.c 10ff496138ffa5bf5c3d9c7808b7558cb9b398d12062c464037167748075a13f
+F src/select.c 8a8b7117bed5b7ce8122b611a9a7ff9504c523de3793d3a26661bf8ad81577ef
 F src/shell.c.in 694aaf751f00610381533d4a31c83d142cfc83ef91ef65e2aa6912ace7c39b40
 F src/sqlite.h.in 7b07a33d2af82ee974aa91e6294abce0282b2f4c5934b291d2fff961810dd867
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
@@ -728,7 +728,7 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c dd843f619ac60d5dadab7109cf402432ba74dde0c301505fd1c202add07659e3
 F src/wal.h c3aa7825bfa2fe0d85bef2db94655f99870a285778baa36307c0a16da32b226a
 F src/walker.c 7c7ea0115345851c3da4e04e2e239a29983b61fb5b038b94eede6aba462640e2
-F src/where.c dbbd8588329e211fc797ee3d48cde21ad7a3ba0f9b135db9f10e5ba44690cf43
+F src/where.c d4240edf4c78b94e705f774509f0552ebcf08a1d2ee169fe14d66eccb4dc910a
 F src/whereInt.h c7d19902863beadec1d04e66aca39c0bcd60b74f05f0eaa7422c7005dfc5d51a
 F src/wherecode.c 5d77db30a2a3dd532492ae882de114edba2fae672622056b1c7fd61f5917a8f1
 F src/whereexpr.c dc5096eca5ed503999be3bdee8a90c51361289a678d396a220912e9cb73b3c00
@@ -2049,8 +2049,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P aa769ee7477171f26a091cadff98aa4f48da7752ade20b405a95c4525456f62e
-R 5d3359f6c6d5e2c6f797651e2c52272a
+P b7ef9796f548ce43e06673f86bbec68157aae5e4ee8451e1d87ee5f70af1bb27
+R b2e3c3d0a4d53532b578742c3846e988
 U drh
-Z d3d190ae3372df83f9be614d98609288
+Z 94c05c39e8f919e5e81448014dcce915
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 1ef995c32e..9736ae7713 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-b7ef9796f548ce43e06673f86bbec68157aae5e4ee8451e1d87ee5f70af1bb27
\ No newline at end of file
+165b9bda243777ae7fb6f51ee7ad58771c581b82ef9a70268eb9764e9e6eba6f
\ No newline at end of file
diff --git a/src/select.c b/src/select.c
index 7a3ba4a6fa..482d7283c3 100644
--- a/src/select.c
+++ b/src/select.c
@@ -7285,6 +7285,14 @@ int sqlite3Select(
       goto select_end;
     }
 
+    /* Do not attempt the usual optimizations (flattening and ORDER BY
+    ** elimination) on a MATERIALIZED common table expression because
+    ** a MATERIALIZED common table expression is an optimization fence.
+    */
+    if( pItem->fg.isCte && pItem->u2.pCteUse->eM10d==M10d_Yes ){
+      continue;
+    }
+
     /* Do not try to flatten an aggregate subquery.
     **
     ** Flattening an aggregate subquery is only possible if the outer query
@@ -7315,21 +7323,14 @@ int sqlite3Select(
     **            (b)  The subquery is part of a join
     **          See forum post 062d576715d277c8
     **
-    ** The above cases might get an incorrect result if ORDER BY is omitted.
-    ** The following constraints are not required for correct answers, but are
-    ** included in order to give developers more control over when a sort
-    ** occurs:
-    **
-    **    (6)   The subquery is really a MATERIALIZED CTE
-    **    (7)   The OmitOrderBy optimization is disabled
+    ** Also retain the ORDER BY if the OmitOrderBy optimization is disabled.
     */
     if( pSub->pOrderBy!=0
      && (p->pOrderBy!=0 || pTabList->nSrc>1)      /* Condition (5) */
      && pSub->pLimit==0                           /* Condition (1) */
      && (pSub->selFlags & SF_OrderByReqd)==0      /* Condition (2) */
      && (p->selFlags & SF_OrderByReqd)==0         /* Condition (3) and (4) */
-     && (pItem->fg.isCte==0 || pItem->u2.pCteUse->eM10d!=M10d_Yes) /* (6) */
-     && OptimizationEnabled(db, SQLITE_OmitOrderBy)                /* (7) */
+     && OptimizationEnabled(db, SQLITE_OmitOrderBy)
     ){
       TREETRACE(0x800,pParse,p,
                 ("omit superfluous ORDER BY on %r FROM-clause subquery\n",i+1));
@@ -7366,11 +7367,6 @@ int sqlite3Select(
       continue;
     }
 
-    /* Do not flatten a MATERIALIZED CTE */
-    if( pItem->fg.isCte && pItem->u2.pCteUse->eM10d==M10d_Yes ){
-      continue;
-    }
-
     if( flattenSubquery(pParse, p, i, isAgg) ){
       if( pParse->nErr ) goto select_end;
       /* This subquery can be absorbed into its parent. */
diff --git a/src/where.c b/src/where.c
index c75834ff59..9992b2053f 100644
--- a/src/where.c
+++ b/src/where.c
@@ -6122,8 +6122,27 @@ WhereInfo *sqlite3WhereBegin(
        if( db->mallocFailed ) goto whereBeginError;
     }
   }
+  assert( pWInfo->pTabList!=0 );
   if( pWInfo->pOrderBy==0 && (db->flags & SQLITE_ReverseOrder)!=0 ){
-     pWInfo->revMask = ALLBITS;
+    for(ii=0; ii<pWInfo->pTabList->nSrc; ii++){
+      /* The PRAGMA reverse_unordered_selects=ON setting (also accessible
+      ** using SQLITE_DBCONFIG_REVERSE_SCANORDER) means to reverse the scan
+      ** order for any table that is part of a query that does not have an
+      ** ORDER BY clause.
+      **
+      ** Except, do not reverse the output from MATERIALIZED common table
+      ** expression that has an internal ORDER BY clause, because a
+      ** MATERIALIZED common table expression is an optimization fence.
+      */
+      SrcItem *pItem = &pWInfo->pTabList->a[ii];
+      if( !pItem->fg.isCte
+       || pItem->u2.pCteUse->eM10d!=M10d_Yes
+       || NEVER(pItem->pSelect==0)
+       || pItem->pSelect->pOrderBy==0
+      ){
+        pWInfo->revMask |= MASKBIT(ii);
+      }
+    }
   }
   if( pParse->nErr ){
     goto whereBeginError;

From 26cf4af5d79775af5ebfb19c46ea9a71655916ef Mon Sep 17 00:00:00 2001
From: drh <>
Date: Wed, 2 Aug 2023 13:29:01 +0000
Subject: [PATCH 4/4] Remove a condition from query flattening that is now
 taken care of by the caller.  Factor out the reverse_unordered_selects
 processing from the main loop of sqlite3WhereBegin() for performance.

FossilOrigin-Name: f068f105fb158634321bf6401f0774c81059932d213a18b627ae98bcffc10912
---
 manifest      | 14 +++++++-------
 manifest.uuid |  2 +-
 src/select.c  |  9 +++++----
 src/where.c   | 42 +++++++++++++++++++++++-------------------
 4 files changed, 36 insertions(+), 31 deletions(-)

diff --git a/manifest b/manifest
index 043e5c2130..4664e580eb 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Simplify\sthe\sselect.c\slogic\sthat\senforces\sthe\soptimization\sfence\saround\na\sMATERIALIZED\scommon\stable\sexpression.\s\sDo\snot\sallow\sthe\nreverse_unordered_selects\ssetting\sto\saffect\sa\sfenced\sCTE\sthat\sitself\shas\nan\sORDER\sBY\sclause.
-D 2023-08-02T12:39:56.675
+C Remove\sa\scondition\sfrom\squery\sflattening\sthat\sis\snow\staken\scare\sof\sby\nthe\scaller.\s\sFactor\sout\sthe\sreverse_unordered_selects\sprocessing\sfrom\sthe\nmain\sloop\sof\ssqlite3WhereBegin()\sfor\sperformance.
+D 2023-08-02T13:29:01.398
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -643,7 +643,7 @@ F src/printf.c e3ba080e2f409f9bfcc8d34724e6fc160e9c718dc92d0548f6b71b8b6f860ce2
 F src/random.c 606b00941a1d7dd09c381d3279a058d771f406c5213c9932bbd93d5587be4b9c
 F src/resolve.c 37953a5f36c60bea413c3c04efcd433b6177009f508ef2ace0494728912fe2e9
 F src/rowset.c 8432130e6c344b3401a8874c3cb49fefe6873fec593294de077afea2dce5ec97
-F src/select.c 8a8b7117bed5b7ce8122b611a9a7ff9504c523de3793d3a26661bf8ad81577ef
+F src/select.c abf48be202d35c4f450325b61992e98ac4aa81ed1e29709069432877d3b555d3
 F src/shell.c.in 694aaf751f00610381533d4a31c83d142cfc83ef91ef65e2aa6912ace7c39b40
 F src/sqlite.h.in 7b07a33d2af82ee974aa91e6294abce0282b2f4c5934b291d2fff961810dd867
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
@@ -728,7 +728,7 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c dd843f619ac60d5dadab7109cf402432ba74dde0c301505fd1c202add07659e3
 F src/wal.h c3aa7825bfa2fe0d85bef2db94655f99870a285778baa36307c0a16da32b226a
 F src/walker.c 7c7ea0115345851c3da4e04e2e239a29983b61fb5b038b94eede6aba462640e2
-F src/where.c d4240edf4c78b94e705f774509f0552ebcf08a1d2ee169fe14d66eccb4dc910a
+F src/where.c b8917792f1e0dbfa28fb29e6cd3d560060d69667be0ba4c491cbc772363264f5
 F src/whereInt.h c7d19902863beadec1d04e66aca39c0bcd60b74f05f0eaa7422c7005dfc5d51a
 F src/wherecode.c 5d77db30a2a3dd532492ae882de114edba2fae672622056b1c7fd61f5917a8f1
 F src/whereexpr.c dc5096eca5ed503999be3bdee8a90c51361289a678d396a220912e9cb73b3c00
@@ -2049,8 +2049,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P b7ef9796f548ce43e06673f86bbec68157aae5e4ee8451e1d87ee5f70af1bb27
-R b2e3c3d0a4d53532b578742c3846e988
+P 165b9bda243777ae7fb6f51ee7ad58771c581b82ef9a70268eb9764e9e6eba6f
+R 2044877763bac67c01e0c206bcedee44
 U drh
-Z 94c05c39e8f919e5e81448014dcce915
+Z 1df9c853e697487617d65f29dca4002a
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 9736ae7713..bed6656874 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-165b9bda243777ae7fb6f51ee7ad58771c581b82ef9a70268eb9764e9e6eba6f
\ No newline at end of file
+f068f105fb158634321bf6401f0774c81059932d213a18b627ae98bcffc10912
\ No newline at end of file
diff --git a/src/select.c b/src/select.c
index 482d7283c3..41e42b6808 100644
--- a/src/select.c
+++ b/src/select.c
@@ -4292,7 +4292,8 @@ static int compoundHasDifferentAffinities(Select *p){
 **        (27b) the subquery is a compound query and the RIGHT JOIN occurs
 **              in any arm of the compound query.  (See also (17g).)
 **
-**  (28)  The subquery is not a MATERIALIZED CTE.
+**  (28)  The subquery is not a MATERIALIZED CTE.  (This is handled
+**        in the caller before ever reaching this routine.)
 **
 **
 ** In this routine, the "p" parameter is a pointer to the outer query.
@@ -4402,9 +4403,9 @@ static int flattenSubquery(
   if( iFrom>0 && (pSubSrc->a[0].fg.jointype & JT_LTORJ)!=0 ){
     return 0;   /* Restriction (27a) */
   }
-  if( pSubitem->fg.isCte && pSubitem->u2.pCteUse->eM10d==M10d_Yes ){
-    return 0;       /* (28) */
-  }
+
+  /* Condition (28) is blocked by the caller */
+  assert( !pSubitem->fg.isCte || pSubitem->u2.pCteUse->eM10d!=M10d_Yes );
 
   /* Restriction (17): If the sub-query is a compound SELECT, then it must
   ** use only the UNION ALL operator. And none of the simple select queries
diff --git a/src/where.c b/src/where.c
index 9992b2053f..213df42230 100644
--- a/src/where.c
+++ b/src/where.c
@@ -5758,6 +5758,28 @@ static SQLITE_NOINLINE void whereAddIndexedExpr(
   }
 }
 
+/*
+** Set the reverse-scan order mask to one for all tables in the query
+** with the exception of MATERIALIZED common table expressions that have
+** their own internal ORDER BY clauses.
+**
+** This implements the PRAGMA reverse_unordered_selects=ON setting.
+** (Also SQLITE_DBCONFIG_REVERSE_SCANORDER).
+*/
+static SQLITE_NOINLINE void whereReverseScanOrder(WhereInfo *pWInfo){
+  int ii;
+  for(ii=0; ii<pWInfo->pTabList->nSrc; ii++){
+    SrcItem *pItem = &pWInfo->pTabList->a[ii];
+    if( !pItem->fg.isCte
+     || pItem->u2.pCteUse->eM10d!=M10d_Yes
+     || NEVER(pItem->pSelect==0)
+     || pItem->pSelect->pOrderBy==0
+    ){
+      pWInfo->revMask |= MASKBIT(ii);
+    }
+  }
+}
+
 /*
 ** Generate the beginning of the loop used for WHERE clause processing.
 ** The return value is a pointer to an opaque structure that contains
@@ -6124,25 +6146,7 @@ WhereInfo *sqlite3WhereBegin(
   }
   assert( pWInfo->pTabList!=0 );
   if( pWInfo->pOrderBy==0 && (db->flags & SQLITE_ReverseOrder)!=0 ){
-    for(ii=0; ii<pWInfo->pTabList->nSrc; ii++){
-      /* The PRAGMA reverse_unordered_selects=ON setting (also accessible
-      ** using SQLITE_DBCONFIG_REVERSE_SCANORDER) means to reverse the scan
-      ** order for any table that is part of a query that does not have an
-      ** ORDER BY clause.
-      **
-      ** Except, do not reverse the output from MATERIALIZED common table
-      ** expression that has an internal ORDER BY clause, because a
-      ** MATERIALIZED common table expression is an optimization fence.
-      */
-      SrcItem *pItem = &pWInfo->pTabList->a[ii];
-      if( !pItem->fg.isCte
-       || pItem->u2.pCteUse->eM10d!=M10d_Yes
-       || NEVER(pItem->pSelect==0)
-       || pItem->pSelect->pOrderBy==0
-      ){
-        pWInfo->revMask |= MASKBIT(ii);
-      }
-    }
+    whereReverseScanOrder(pWInfo);
   }
   if( pParse->nErr ){
     goto whereBeginError;