From 90fa4c7b2c7653cb64a4662bc98ea73d12143b43 Mon Sep 17 00:00:00 2001
From: drh <>
Date: Sat, 31 Aug 2024 14:31:17 +0000
Subject: [PATCH 1/5] Enhance the percentile() and median() extension functions
 so that they can be window functions.

FossilOrigin-Name: 4d0e3df4b9c609755977b8a462126242d2be1310c0122a8d4ba76d98d32a7230
---
 Makefile.in           |  3 +-
 Makefile.msc          |  1 +
 ext/misc/percentile.c | 96 +++++++++++++++++++++++++++++++++++++------
 main.mk               |  1 +
 manifest              | 23 ++++++-----
 manifest.uuid         |  2 +-
 src/func.c            |  8 +++-
 7 files changed, 108 insertions(+), 26 deletions(-)

diff --git a/Makefile.in b/Makefile.in
index 188f94d701..9fcf87f941 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -1182,6 +1182,7 @@ SHELL_DEP = \
     $(TOP)/ext/misc/ieee754.c \
     $(TOP)/ext/misc/memtrace.c \
     $(TOP)/ext/misc/pcachetrace.c \
+    $(TOP)/ext/misc/percentile.c \
     $(TOP)/ext/misc/regexp.c \
     $(TOP)/ext/misc/series.c \
     $(TOP)/ext/misc/shathree.c \
@@ -1390,7 +1391,7 @@ srctree-check:	$(TOP)/tool/srctree-check.tcl
 
 # Testing for a release
 #
-releasetest: srctree-check has_tclsh85
+releasetest: srctree-check has_tclsh85 verify-source
 	$(TCLSH_CMD) $(TOP)/test/testrunner.tcl release $(TSTRNNR_OPTS)
 
 # Minimal testing that runs in less than 3 minutes
diff --git a/Makefile.msc b/Makefile.msc
index bf707edfd6..27513da12f 100644
--- a/Makefile.msc
+++ b/Makefile.msc
@@ -2313,6 +2313,7 @@ SHELL_DEP = \
     $(TOP)\ext\misc\ieee754.c \
     $(TOP)\ext\misc\memtrace.c \
     $(TOP)\ext\misc\pcachetrace.c \
+    $(TOP)\ext\misc\percentile.c \
     $(TOP)\ext\misc\regexp.c \
     $(TOP)\ext\misc\series.c \
     $(TOP)\ext\misc\shathree.c \
diff --git a/ext/misc/percentile.c b/ext/misc/percentile.c
index cccbaf0253..99b1430171 100644
--- a/ext/misc/percentile.c
+++ b/ext/misc/percentile.c
@@ -77,6 +77,7 @@ typedef struct Percentile Percentile;
 struct Percentile {
   unsigned nAlloc;     /* Number of slots allocated for a[] */
   unsigned nUsed;      /* Number of slots actually used in a[] */
+  char bSorted;        /* True if a[] is already in sorted order */
   double rPct;         /* 1.0 more than the value for P */
   double *a;           /* Array of Y values */
 };
@@ -183,10 +184,65 @@ static void percentStep(sqlite3_context *pCtx, int argc, sqlite3_value **argv){
     p->a = a;
   }
   p->a[p->nUsed++] = y;
+  assert( p->nUsed>=1 );
+  if( p->nUsed==1 ){
+    p->bSorted = 1;
+  }else if( p->bSorted && p->a[p->nUsed-2]>y ){
+    p->bSorted = 0;
+  }
+}
+
+/*
+** The "inverse" function for percentile(Y,P) is called to remove a
+** row that was previously inserted by "step".
+*/
+static void percentInverse(sqlite3_context *pCtx,int argc,sqlite3_value **argv){
+  Percentile *p;
+  int eType;
+  double y;
+  int i;
+  assert( argc==2 || argc==1 );
+
+  /* Allocate the session context. */
+  p = (Percentile*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  assert( p!=0 );
+
+  /* Ignore rows for which Y is NULL */
+  eType = sqlite3_value_type(argv[0]);
+  if( eType==SQLITE_NULL ) return;
+
+  /* If not NULL, then Y must be numeric.  Otherwise throw an error.
+  ** Requirement 4 */
+  if( eType!=SQLITE_INTEGER && eType!=SQLITE_FLOAT ){
+    return;
+  }
+
+  /* Ignore the Y value if it is infinity or NaN */
+  y = sqlite3_value_double(argv[0]);
+  if( isInfinity(y) ){
+    return;
+  }
+
+  /* Find and remove the row */
+  for(i=0; i<p->nUsed && p->a[i]!=y; i++){}
+  if( i<p->nUsed ){
+    p->a[i] = p->a[p->nUsed-1];
+    p->nUsed--;
+  }
+  p->bSorted = p->nUsed<=1;
 }
 
 /*
 ** Sort an array of doubles.
+**
+** Algorithm: quicksort
+**
+** This is implemented separately rather than using the qsort() routine
+** from the standard library because:
+**
+**    (1)  To avoid a dependency on qsort()
+**    (2)  To avoid the function call to the comparison routine for each
+**         comparison.
 */
 static void sortDoubles(double *a, int n){
   int iLt;       /* Entries with index less than iLt are less than rPivot */
@@ -238,7 +294,7 @@ static void sortDoubles(double *a, int n){
 ** Called to compute the final output of percentile() and to clean
 ** up all allocated memory.
 */
-static void percentFinal(sqlite3_context *pCtx){
+static void percentCompute(sqlite3_context *pCtx, int bIsFinal){
   Percentile *p;
   unsigned i1, i2;
   double v1, v2;
@@ -247,7 +303,10 @@ static void percentFinal(sqlite3_context *pCtx){
   if( p==0 ) return;
   if( p->a==0 ) return;
   if( p->nUsed ){
-    sortDoubles(p->a, p->nUsed);
+    if( p->bSorted==0 ){
+      sortDoubles(p->a, p->nUsed);
+      p->bSorted = 1;
+    }
     ix = (p->rPct-1.0)*(p->nUsed-1)*0.01;
     i1 = (unsigned)ix;
     i2 = ix==(double)i1 || i1==p->nUsed-1 ? i1 : i1+1;
@@ -256,9 +315,18 @@ static void percentFinal(sqlite3_context *pCtx){
     vx = v1 + (v2-v1)*(ix-i1);
     sqlite3_result_double(pCtx, vx);
   }
-  sqlite3_free(p->a);
-  memset(p, 0, sizeof(*p));
+  if( bIsFinal ){
+    sqlite3_free(p->a);
+    memset(p, 0, sizeof(*p));
+  }
 }
+static void percentFinal(sqlite3_context *pCtx){
+  percentCompute(pCtx, 1);
+}
+static void percentValue(sqlite3_context *pCtx){
+  percentCompute(pCtx, 0);
+}
+
 
 
 #ifdef _WIN32
@@ -272,18 +340,22 @@ int sqlite3_percentile_init(
   int rc = SQLITE_OK;
   SQLITE_EXTENSION_INIT2(pApi);
   (void)pzErrMsg;  /* Unused parameter */
-  rc = sqlite3_create_function(db, "percentile", 2, 
-                               SQLITE_UTF8|SQLITE_INNOCUOUS, 0,
-                               0, percentStep, percentFinal);
-  if( rc==SQLITE_OK ){
-    rc = sqlite3_create_function(db, "median", 1, 
+  rc = sqlite3_create_window_function(db, "percentile", 2, 
                                  SQLITE_UTF8|SQLITE_INNOCUOUS, 0,
-                                 0, percentStep, percentFinal);
+                                 percentStep, percentFinal,
+                                 percentValue, percentInverse, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_window_function(db, "median", 1, 
+                                 SQLITE_UTF8|SQLITE_INNOCUOUS, 0,
+                                 percentStep, percentFinal,
+                                 percentValue, percentInverse, 0);
+
   }
   if( rc==SQLITE_OK ){
-    rc = sqlite3_create_function(db, "percentile_cont", 2, 
+    rc = sqlite3_create_window_function(db, "percentile_cont", 2, 
                                  SQLITE_UTF8|SQLITE_INNOCUOUS, &percentStep,
-                                 0, percentStep, percentFinal);
+                                 percentStep, percentFinal,
+                                 percentValue, percentInverse, 0);
   }
   return rc;
 }
diff --git a/main.mk b/main.mk
index b1c86a1b76..1f32c22bdf 100644
--- a/main.mk
+++ b/main.mk
@@ -764,6 +764,7 @@ SHELL_DEP = \
     $(TOP)/ext/misc/ieee754.c \
     $(TOP)/ext/misc/memtrace.c \
     $(TOP)/ext/misc/pcachetrace.c \
+    $(TOP)/ext/misc/percentile.c \
     $(TOP)/ext/misc/regexp.c \
     $(TOP)/ext/misc/series.c \
     $(TOP)/ext/misc/shathree.c \
diff --git a/manifest b/manifest
index 25793c4244..4190a7f8da 100644
--- a/manifest
+++ b/manifest
@@ -1,11 +1,11 @@
-C Do\snot\sfail\sthe\somittest\sif\sICU\slibraries\sare\snot\sinstalled.
-D 2024-08-30T17:33:25.286
+C Enhance\sthe\spercentile()\sand\smedian()\sextension\sfunctions\sso\sthat\sthey\scan\sbe\nwindow\sfunctions.
+D 2024-08-31T14:31:17.092
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
-F Makefile.in 77627cbeeffe23606da5663458c0f8bbb86d28e2aca270a5d9b0db8e39a54bb2
+F Makefile.in 394e8c4b17d7a25b26a379573cb74bac569e6e4e9b5f1e2cf6efd53866867054
 F Makefile.linux-gcc f3842a0b1efbfbb74ac0ef60e56b301836d05b4d867d014f714fa750048f1ab6
-F Makefile.msc 47dfd26a401c5a33e237ecfe126c996977f34ac44e44a1a1ebf2204abb89d483
+F Makefile.msc 8dc55cc46fabd6a01afca3a5829c4cb69b99537e42143ca6f0bf6e811b9f5068
 F README.md 5b678e264236788390d11991f2c0052bd73f19790173883fc56d638bcb849154
 F VERSION 0db40f92c04378404eb45bff93e9e42c148c7e54fd3da99469ed21e22411f5a6
 F aclocal.m4 a5c22d164aff7ed549d53a90fa56d56955281f50
@@ -410,7 +410,7 @@ F ext/misc/nextchar.c 7877914c2a80c2f181dd04c3dbef550dfb54c93495dc03da2403b5dd58
 F ext/misc/noop.c f1a21cc9b7a4e667e5c8458d80ba680b8bd4315a003f256006046879f679c5a0
 F ext/misc/normalize.c bd84355c118e297522aba74de34a4fd286fc775524e0499b14473918d09ea61f
 F ext/misc/pcachetrace.c f4227ce03fb16aa8d6f321b72dd051097419d7a028a9853af048bee7645cb405
-F ext/misc/percentile.c af1941dc87d45dd0c2698a3087fbfe9ee0d157e5e72da521430c4b784abcbe81
+F ext/misc/percentile.c 89416b108569171be1d8dda4fa2687ad116ea969b4d129d02cf3dc1fd67fc87e
 F ext/misc/prefixes.c 82645f79229877afab08c8b08ca1e7fa31921280906b90a61c294e4f540cd2a6
 F ext/misc/qpvtab.c fc189e127f68f791af90a487f4460ec91539a716daf45a0c357e963fd47cc06c
 F ext/misc/randomjson.c ef835fc64289e76ac4873b85fe12f9463a036168d7683cf2b773e36e6262c4ed
@@ -685,7 +685,7 @@ F ext/wasm/wasmfs.make 8a4955882aaa0783b3f60a9484a1f0f3d8b6f775c0fcd17c082f31966
 F install-sh 9d4de14ab9fb0facae2f48780b874848cbf2f895 x
 F ltmain.sh 3ff0879076df340d2e23ae905484d8c15d5fdea8
 F magic.txt 5ade0bc977aa135e79e3faaea894d5671b26107cc91e70783aa7dc83f22f3ba0
-F main.mk 40f8cd07372d7eed2fe33403a42b82c3f5d2d46b59480444384326db70bb33f1
+F main.mk de83918046afeb0ac4239e88511623f3ef2a0c41aab0e2b401e0275f4fd24a8e
 F mptest/config01.test 3c6adcbc50b991866855f1977ff172eb6d901271
 F mptest/config02.test 4415dfe36c48785f751e16e32c20b077c28ae504
 F mptest/crash01.test 61e61469e257df0850df4293d7d4d6c2af301421
@@ -718,7 +718,7 @@ F src/delete.c 444c4d1eaac40103461e3b6f0881846dd3aafc1cec1dd169d3482fa331667da7
 F src/expr.c 6d5f2c38fe3ec06a7eac599dac822788b36064124e20112a844e9cd5156cb239
 F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
 F src/fkey.c 928ed2517e8732113d2b9821aa37af639688d752f4ea9ac6e0e393d713eeb76f
-F src/func.c 1f61e32e7a357e615b5d2e774bee563761fce4f2fd97ecb0f72c33e62a2ada5f
+F src/func.c df400a1d3f4625997d4dd8a81951c303e066277c29b861d37e03cd152d7858dd
 F src/global.c 61a419dd9e993b9be0f91de4c4ccf322b053eb829868e089f0321dd669be3b90
 F src/hash.c 9ee4269fb1d6632a6fecfb9479c93a1f29271bddbbaf215dd60420bcb80c7220
 F src/hash.h 3340ab6e1d13e725571d7cee6d3e3135f0779a7d8e76a9ce0a85971fa3953c51
@@ -2211,8 +2211,11 @@ F vsixtest/vsixtest.tcl 6195aba1f12a5e10efc2b8c0009532167be5e301abe5b31385638080
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P e48add02695a41b26a04e7942b5333e2bf4dc5598e363367aea3a4690982667d
-R 3b9cf08a862640c366f07bc714e510b5
+P ddc55efd2d59df3f20743b0533550436da945453c069025a3f871d28d40e13d4
+R 5abe90c6c09c8e29fb97dabd43182a07
+T *branch * percentile-window
+T *sym-percentile-window *
+T -sym-trunk *
 U drh
-Z ce5d41834ddc15c40aed5b812cb5e6fa
+Z 85a1ed3baf7191136421a56e2c79709a
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 0044aadb49..ac02b4544f 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-ddc55efd2d59df3f20743b0533550436da945453c069025a3f871d28d40e13d4
+4d0e3df4b9c609755977b8a462126242d2be1310c0122a8d4ba76d98d32a7230
diff --git a/src/func.c b/src/func.c
index 8fcda11dc0..a634a7fbea 100644
--- a/src/func.c
+++ b/src/func.c
@@ -2049,7 +2049,11 @@ static void minMaxFinalize(sqlite3_context *context){
 ** group_concat(EXPR, ?SEPARATOR?)
 ** string_agg(EXPR, SEPARATOR)
 **
-** The SEPARATOR goes before the EXPR string.  This is tragic.  The
+** Content is accumulated in GroupConcatCtx.str with the SEPARATOR
+** coming before the EXPR value, except for the first entry which
+** omits the SEPARATOR.
+**
+** It is tragic that the SEPARATOR goes before the EXPR string.  The
 ** groupConcatInverse() implementation would have been easier if the
 ** SEPARATOR were appended after EXPR.  And the order is undocumented,
 ** so we could change it, in theory.  But the old behavior has been
@@ -2153,7 +2157,7 @@ static void groupConcatInverse(
   /* pGCC is always non-NULL since groupConcatStep() will have always
   ** run first to initialize it */
   if( ALWAYS(pGCC) ){
-    int nVS;
+    int nVS;  /* Number of characters to remove */
     /* Must call sqlite3_value_text() to convert the argument into text prior
     ** to invoking sqlite3_value_bytes(), in case the text encoding is UTF16 */
     (void)sqlite3_value_text(argv[0]);

From 129767958ae41bf0da17b69643ca061a8d4f5620 Mon Sep 17 00:00:00 2001
From: drh <>
Date: Sat, 31 Aug 2024 15:02:07 +0000
Subject: [PATCH 2/5] Test cases added.

FossilOrigin-Name: 25e68229843cc84978955817285550085d1306ba4ce3b0517dd00e5d05b9ae0a
---
 manifest             | 15 +++++-------
 manifest.uuid        |  2 +-
 test/percentile.test | 58 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+), 10 deletions(-)

diff --git a/manifest b/manifest
index 4190a7f8da..e61e0275b4 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Enhance\sthe\spercentile()\sand\smedian()\sextension\sfunctions\sso\sthat\sthey\scan\sbe\nwindow\sfunctions.
-D 2024-08-31T14:31:17.092
+C Test\scases\sadded.
+D 2024-08-31T15:02:07.805
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -1517,7 +1517,7 @@ F test/parser1.test 6ccdf5e459a5dc4673d3273dc311a7e9742ca952dd0551a6a6320d27035c
 F test/pcache.test c8acbedd3b6fd0f9a7ca887a83b11d24a007972b
 F test/pcache2.test af7f3deb1a819f77a6d0d81534e97d1cf62cd442
 F test/pendingrace.test e99efc5ab3584da3dfc8cd6a0ec4e5a42214820574f5ea24ee93f1d84655f463
-F test/percentile.test 74e383216a075251512d6ba98beb9dccd6da465e3f73817fc438379e3a628de7
+F test/percentile.test b30d92480943de8236c1522cace227ad354512ade699789636a4f50ba8a790a1
 F test/permutations.test 405542f1d659942994a6b38a9e024cf5cfd23eaa68c806aeb24a72d7c9186e80
 F test/pg_common.tcl 3b27542224db1e713ae387459b5d117c836a5f6e328846922993b6d2b7640d9f
 F test/pragma.test 11cb9310c42f921918f7f563e3c0b6e70f9f9c3a6a1cf12af8fccb6c574f3882
@@ -2211,11 +2211,8 @@ F vsixtest/vsixtest.tcl 6195aba1f12a5e10efc2b8c0009532167be5e301abe5b31385638080
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P ddc55efd2d59df3f20743b0533550436da945453c069025a3f871d28d40e13d4
-R 5abe90c6c09c8e29fb97dabd43182a07
-T *branch * percentile-window
-T *sym-percentile-window *
-T -sym-trunk *
+P 4d0e3df4b9c609755977b8a462126242d2be1310c0122a8d4ba76d98d32a7230
+R 06b03a21c6b126e146ea802b7b43139b
 U drh
-Z 85a1ed3baf7191136421a56e2c79709a
+Z a8a75faed57aa0d8766eb4f3377323de
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index ac02b4544f..301d4eacfd 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-4d0e3df4b9c609755977b8a462126242d2be1310c0122a8d4ba76d98d32a7230
+25e68229843cc84978955817285550085d1306ba4ce3b0517dd00e5d05b9ae0a
diff --git a/test/percentile.test b/test/percentile.test
index ab5b4883fd..92c2010f4b 100644
--- a/test/percentile.test
+++ b/test/percentile.test
@@ -229,4 +229,62 @@ ifcapable vtab {
   }
 }
 
+# median() as a window function.  (2024-08-31)
+#
+do_execsql_test percentile-3.0 {
+  DROP TABLE IF EXISTS t1;
+  CREATE TABLE t1(a INTEGER PRIMARY KEY, b, c, d);
+  INSERT INTO t1 VALUES (1, 'A', 'one',   8.4),
+                        (2, 'B', 'two',   7.1),
+                        (3, 'C', 'three', 5.9),
+                        (4, 'D', 'one',  11.0),
+                        (5, 'E', 'two',  12.5),
+                        (6, 'F', 'three', 0.0),
+                        (7, 'G', 'one',   2.7);
+}
+do_execsql_test percentile-3.1 {
+SELECT a, b, c, d,
+       group_concat(b,'.') OVER W1 AS 'elements',
+       median(d) OVER W1 AS 'median'
+  FROM t1
+ WINDOW W1 AS (ORDER BY c, a ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
+} {
+  1  A  one    8.4   A.D       9.7   
+  4  D  one    11.0  A.D.G     8.4   
+  7  G  one    2.7   D.G.C     5.9   
+  3  C  three  5.9   G.C.F     2.7   
+  6  F  three  0.0   C.F.B     5.9   
+  2  B  two    7.1   F.B.E     7.1   
+  5  E  two    12.5  B.E       9.8   
+}
+do_execsql_test percentile-3.2 {
+SELECT a, b, c, d,
+       group_concat(b,'.') OVER W1 AS 'elements',
+       median(d) OVER W1 AS 'median'
+  FROM t1
+ WINDOW W1 AS (ORDER BY c, a ROWS BETWEEN UNBOUNDED PRECEDING AND 1 FOLLOWING)
+} {
+  1  A  one    8.4   A.D            9.7   
+  4  D  one    11.0  A.D.G          8.4   
+  7  G  one    2.7   A.D.G.C        7.15  
+  3  C  three  5.9   A.D.G.C.F      5.9   
+  6  F  three  0.0   A.D.G.C.F.B    6.5   
+  2  B  two    7.1   A.D.G.C.F.B.E  7.1   
+  5  E  two    12.5  A.D.G.C.F.B.E  7.1   
+}
+do_execsql_test percentile-3.3 {
+SELECT a, b, c, d,
+       group_concat(b,'.') OVER W1 AS 'elements',
+       median(d) OVER W1 AS 'median'
+  FROM t1
+ WINDOW W1 AS (ORDER BY c, a ROWS BETWEEN 1 PRECEDING AND UNBOUNDED FOLLOWING)
+} {
+  1  A  one    8.4   A.D.G.C.F.B.E  7.1   
+  4  D  one    11.0  A.D.G.C.F.B.E  7.1   
+  7  G  one    2.7   D.G.C.F.B.E    6.5   
+  3  C  three  5.9   G.C.F.B.E      5.9   
+  6  F  three  0.0   C.F.B.E        6.5   
+  2  B  two    7.1   F.B.E          7.1   
+  5  E  two    12.5  B.E            9.8   
+}
 finish_test

From ad8ec9db63f0da294625211d6f261d99685fb971 Mon Sep 17 00:00:00 2001
From: drh <>
Date: Sat, 31 Aug 2024 16:55:14 +0000
Subject: [PATCH 3/5] Avoid unnecessary sort operations when running one of the
 percentile aggregates as a window function.

FossilOrigin-Name: 5d311536211eb1e3c887ceb7e6516d3900e6eebbccc8c445dd43cdd556182728
---
 ext/misc/percentile.c | 196 ++++++++++++++++++++++++++++++------------
 manifest              |  12 +--
 manifest.uuid         |   2 +-
 3 files changed, 149 insertions(+), 61 deletions(-)

diff --git a/ext/misc/percentile.c b/ext/misc/percentile.c
index 99b1430171..e427497878 100644
--- a/ext/misc/percentile.c
+++ b/ext/misc/percentile.c
@@ -62,6 +62,29 @@
 **
 **  (14)  A separate percentile_cond(Y,X) function is the equivalent of
 **        percentile(Y,X*100.0).
+**
+**  (15)  All three SQL functions implemented by this module can also be
+**        used as window-functions.
+**
+** Implementation notes as of 2024-08-31:
+**
+**  *  The regular aggregate-function versions of the merge(), percentile(),
+**     and percentile_cond() routines work by accumulating all values in
+**     an array of doubles, then sorting that array using a quicksort
+**     before computing the answer.  Thus the runtime is O(NlogN) where
+**     N is the number of rows of input.
+**
+**  *  For the window-function versions of these routines, the array of
+**     inputs is sorted as soon as the first value is computed.  Thereafter,
+**     the array is kept in sorted order using an insert-sort.  This
+**     results in O(N*K) performance where K is the size of the window.
+**     One can devise alternative implementations that give O(N*logN*logK)
+**     performance, but they require more complex logic and data structures.
+**     The developers have elected to keep the asymptotically slower
+**     algorithm for now, for simplicity, under the theory that window
+**     functions are seldom used and when they are, the window size K is
+**     often small.  The developers might revisit that decision later,
+**     should the need arise.
 */
 #include "sqlite3ext.h"
 SQLITE_EXTENSION_INIT1
@@ -78,6 +101,7 @@ struct Percentile {
   unsigned nAlloc;     /* Number of slots allocated for a[] */
   unsigned nUsed;      /* Number of slots actually used in a[] */
   char bSorted;        /* True if a[] is already in sorted order */
+  char bKeepSorted;    /* True if advantageous to keep a[] sorted */
   double rPct;         /* 1.0 more than the value for P */
   double *a;           /* Array of Y values */
 };
@@ -85,7 +109,7 @@ struct Percentile {
 /*
 ** Return TRUE if the input floating-point number is an infinity.
 */
-static int isInfinity(double r){
+static int percentIsInfinity(double r){
   sqlite3_uint64 u;
   assert( sizeof(u)==sizeof(r) );
   memcpy(&u, &r, sizeof(u));
@@ -93,13 +117,55 @@ static int isInfinity(double r){
 }
 
 /*
-** Return TRUE if two doubles differ by 0.001 or less
+** Return TRUE if two doubles differ by 0.001 or less.
 */
-static int sameValue(double a, double b){
+static int percentSameValue(double a, double b){
   a -= b;
   return a>=-0.001 && a<=0.001;
 }
 
+#if 0
+/* Verify that the elements of the Percentile p are in fact sorted.
+** Used for testing and debugging only.
+*/
+static void percentAssertSorted(Percentile *p){
+  int i;
+  for(i=p->nUsed-2; i>=0 && p->a[i]<=p->a[i+1]; i--){}
+  assert( i<0 );
+}
+#else
+# define percentAssertSorted(X)
+#endif
+
+/*
+** Search p (which must have p->bSorted) looking for an entry with
+** value y.  Return the index of that entry.
+**
+** If bExact is true, return -1 if the entry is not found.
+**
+** If bExact is false, return the index at which a new entry with
+** value y should be insert in order to keep the values in sorted
+** order.  The smallest return value in this case will be 0, and
+** the largest return value will be p->nUsed.
+*/
+static int percentBinarySearch(Percentile *p, double y, int bExact){
+  int iFirst = 0;              /* First element of search range */
+  int iLast = p->nUsed - 1;    /* Last element of search range */
+  while( iLast>=iFirst ){
+    int iMid = (iFirst+iLast)/2;
+    double x = p->a[iMid];
+    if( x<y ){
+      iFirst = iMid + 1;
+    }else if( x>y ){
+      iLast = iMid - 1;
+    }else{
+      return iMid;
+    }
+  }
+  if( bExact ) return -1;
+  return iFirst;
+}
+
 /*
 ** The "step" function for percentile(Y,P) is called once for each
 ** input row.
@@ -145,7 +211,7 @@ static void percentStep(sqlite3_context *pCtx, int argc, sqlite3_value **argv){
   ** from any prior row, per Requirement (2). */
   if( p->rPct==0.0 ){
     p->rPct = rPct+1.0;
-  }else if( !sameValue(p->rPct,rPct+1.0) ){
+  }else if( !percentSameValue(p->rPct,rPct+1.0) ){
     sqlite3_result_error(pCtx, "2nd argument to percentile() is not the "
                                "same for all input rows", -1);
     return;
@@ -165,7 +231,7 @@ static void percentStep(sqlite3_context *pCtx, int argc, sqlite3_value **argv){
 
   /* Throw an error if the Y value is infinity or NaN */
   y = sqlite3_value_double(argv[0]);
-  if( isInfinity(y) ){
+  if( percentIsInfinity(y) ){
     sqlite3_result_error(pCtx, "Inf input to percentile()", -1);
     return;
   }
@@ -183,55 +249,26 @@ static void percentStep(sqlite3_context *pCtx, int argc, sqlite3_value **argv){
     p->nAlloc = n;
     p->a = a;
   }
-  p->a[p->nUsed++] = y;
-  assert( p->nUsed>=1 );
-  if( p->nUsed==1 ){
+  if( p->nUsed==0 ){
+    p->a[p->nUsed++] = y;
     p->bSorted = 1;
-  }else if( p->bSorted && p->a[p->nUsed-2]>y ){
+  }else if( !p->bSorted || y>=p->a[p->nUsed-1] ){
+    p->a[p->nUsed++] = y;
+  }else if( p->bKeepSorted ){
+    int i;
+    percentAssertSorted(p);
+    i = percentBinarySearch(p, y, 0);
+    if( i<p->nUsed ){
+      memmove(&p->a[i+1], &p->a[i], (p->nUsed-i)*sizeof(p->a[0]));
+    }
+    p->a[i] = y;
+    p->nUsed++;
+  }else{
+    p->a[p->nUsed++] = y;
     p->bSorted = 0;
   }
 }
 
-/*
-** The "inverse" function for percentile(Y,P) is called to remove a
-** row that was previously inserted by "step".
-*/
-static void percentInverse(sqlite3_context *pCtx,int argc,sqlite3_value **argv){
-  Percentile *p;
-  int eType;
-  double y;
-  int i;
-  assert( argc==2 || argc==1 );
-
-  /* Allocate the session context. */
-  p = (Percentile*)sqlite3_aggregate_context(pCtx, sizeof(*p));
-  assert( p!=0 );
-
-  /* Ignore rows for which Y is NULL */
-  eType = sqlite3_value_type(argv[0]);
-  if( eType==SQLITE_NULL ) return;
-
-  /* If not NULL, then Y must be numeric.  Otherwise throw an error.
-  ** Requirement 4 */
-  if( eType!=SQLITE_INTEGER && eType!=SQLITE_FLOAT ){
-    return;
-  }
-
-  /* Ignore the Y value if it is infinity or NaN */
-  y = sqlite3_value_double(argv[0]);
-  if( isInfinity(y) ){
-    return;
-  }
-
-  /* Find and remove the row */
-  for(i=0; i<p->nUsed && p->a[i]!=y; i++){}
-  if( i<p->nUsed ){
-    p->a[i] = p->a[p->nUsed-1];
-    p->nUsed--;
-  }
-  p->bSorted = p->nUsed<=1;
-}
-
 /*
 ** Sort an array of doubles.
 **
@@ -290,9 +327,59 @@ static void sortDoubles(double *a, int n){
 #endif
 }
 
+
 /*
-** Called to compute the final output of percentile() and to clean
-** up all allocated memory.
+** The "inverse" function for percentile(Y,P) is called to remove a
+** row that was previously inserted by "step".
+*/
+static void percentInverse(sqlite3_context *pCtx,int argc,sqlite3_value **argv){
+  Percentile *p;
+  int eType;
+  double y;
+  int i;
+  assert( argc==2 || argc==1 );
+
+  /* Allocate the session context. */
+  p = (Percentile*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  assert( p!=0 );
+
+  /* Ignore rows for which Y is NULL */
+  eType = sqlite3_value_type(argv[0]);
+  if( eType==SQLITE_NULL ) return;
+
+  /* If not NULL, then Y must be numeric.  Otherwise throw an error.
+  ** Requirement 4 */
+  if( eType!=SQLITE_INTEGER && eType!=SQLITE_FLOAT ){
+    return;
+  }
+
+  /* Ignore the Y value if it is infinity or NaN */
+  y = sqlite3_value_double(argv[0]);
+  if( percentIsInfinity(y) ){
+    return;
+  }
+  if( p->bSorted==0 ){
+    sortDoubles(p->a, p->nUsed);
+    p->bSorted = 1;
+  }else{
+    percentAssertSorted(p);
+  }
+  p->bKeepSorted = 1;
+
+  /* Find and remove the row */
+  i = percentBinarySearch(p, y, 1);
+  if( i>=0 ){
+    p->nUsed--;
+    if( i<p->nUsed ){
+      memmove(&p->a[i], &p->a[i+1], (p->nUsed - i)*sizeof(p->a[0]));
+    }
+  }
+  percentAssertSorted(p);
+}
+
+/*
+** Compute the final output of percentile().  Clean up all allocated
+** memory if and only if bIsFinal is true.
 */
 static void percentCompute(sqlite3_context *pCtx, int bIsFinal){
   Percentile *p;
@@ -306,6 +393,8 @@ static void percentCompute(sqlite3_context *pCtx, int bIsFinal){
     if( p->bSorted==0 ){
       sortDoubles(p->a, p->nUsed);
       p->bSorted = 1;
+    }else{
+      percentAssertSorted(p);
     }
     ix = (p->rPct-1.0)*(p->nUsed-1)*0.01;
     i1 = (unsigned)ix;
@@ -318,6 +407,8 @@ static void percentCompute(sqlite3_context *pCtx, int bIsFinal){
   if( bIsFinal ){
     sqlite3_free(p->a);
     memset(p, 0, sizeof(*p));
+  }else{
+    p->bKeepSorted = 1;
   }
 }
 static void percentFinal(sqlite3_context *pCtx){
@@ -327,8 +418,6 @@ static void percentValue(sqlite3_context *pCtx){
   percentCompute(pCtx, 0);
 }
 
-
-
 #ifdef _WIN32
 __declspec(dllexport)
 #endif
@@ -349,7 +438,6 @@ int sqlite3_percentile_init(
                                  SQLITE_UTF8|SQLITE_INNOCUOUS, 0,
                                  percentStep, percentFinal,
                                  percentValue, percentInverse, 0);
-
   }
   if( rc==SQLITE_OK ){
     rc = sqlite3_create_window_function(db, "percentile_cont", 2, 
diff --git a/manifest b/manifest
index e61e0275b4..e4debfefcd 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Test\scases\sadded.
-D 2024-08-31T15:02:07.805
+C Avoid\sunnecessary\ssort\soperations\swhen\srunning\sone\sof\sthe\spercentile\naggregates\sas\sa\swindow\sfunction.
+D 2024-08-31T16:55:14.747
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -410,7 +410,7 @@ F ext/misc/nextchar.c 7877914c2a80c2f181dd04c3dbef550dfb54c93495dc03da2403b5dd58
 F ext/misc/noop.c f1a21cc9b7a4e667e5c8458d80ba680b8bd4315a003f256006046879f679c5a0
 F ext/misc/normalize.c bd84355c118e297522aba74de34a4fd286fc775524e0499b14473918d09ea61f
 F ext/misc/pcachetrace.c f4227ce03fb16aa8d6f321b72dd051097419d7a028a9853af048bee7645cb405
-F ext/misc/percentile.c 89416b108569171be1d8dda4fa2687ad116ea969b4d129d02cf3dc1fd67fc87e
+F ext/misc/percentile.c 46627b7495c69344d384f667bb6c80ba2c4aeb779997a4e22fea1a39cd20beb9
 F ext/misc/prefixes.c 82645f79229877afab08c8b08ca1e7fa31921280906b90a61c294e4f540cd2a6
 F ext/misc/qpvtab.c fc189e127f68f791af90a487f4460ec91539a716daf45a0c357e963fd47cc06c
 F ext/misc/randomjson.c ef835fc64289e76ac4873b85fe12f9463a036168d7683cf2b773e36e6262c4ed
@@ -2211,8 +2211,8 @@ F vsixtest/vsixtest.tcl 6195aba1f12a5e10efc2b8c0009532167be5e301abe5b31385638080
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 4d0e3df4b9c609755977b8a462126242d2be1310c0122a8d4ba76d98d32a7230
-R 06b03a21c6b126e146ea802b7b43139b
+P 25e68229843cc84978955817285550085d1306ba4ce3b0517dd00e5d05b9ae0a
+R 1b58d4d1990506055e066a3b56b6ff9a
 U drh
-Z a8a75faed57aa0d8766eb4f3377323de
+Z 10ad6a710202821993e7562cc60a54b3
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 301d4eacfd..1413d7e77e 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-25e68229843cc84978955817285550085d1306ba4ce3b0517dd00e5d05b9ae0a
+5d311536211eb1e3c887ceb7e6516d3900e6eebbccc8c445dd43cdd556182728

From f138110dfdfac0e17f0539521e40e5d9550602cd Mon Sep 17 00:00:00 2001
From: drh <>
Date: Sat, 31 Aug 2024 17:27:55 +0000
Subject: [PATCH 4/5] Add more test cases.

FossilOrigin-Name: 0d0e5456793b4bef673ebc7fcc1c393a6d3c817363d948ddfe06d60eab56dc24
---
 manifest             | 12 +++++------
 manifest.uuid        |  2 +-
 test/percentile.test | 47 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 7 deletions(-)

diff --git a/manifest b/manifest
index e4debfefcd..df07cca990 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Avoid\sunnecessary\ssort\soperations\swhen\srunning\sone\sof\sthe\spercentile\naggregates\sas\sa\swindow\sfunction.
-D 2024-08-31T16:55:14.747
+C Add\smore\stest\scases.
+D 2024-08-31T17:27:55.143
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -1517,7 +1517,7 @@ F test/parser1.test 6ccdf5e459a5dc4673d3273dc311a7e9742ca952dd0551a6a6320d27035c
 F test/pcache.test c8acbedd3b6fd0f9a7ca887a83b11d24a007972b
 F test/pcache2.test af7f3deb1a819f77a6d0d81534e97d1cf62cd442
 F test/pendingrace.test e99efc5ab3584da3dfc8cd6a0ec4e5a42214820574f5ea24ee93f1d84655f463
-F test/percentile.test b30d92480943de8236c1522cace227ad354512ade699789636a4f50ba8a790a1
+F test/percentile.test 4c84880c6d5ca216206a92b6cb33c2fb27c972bec6afc6f5a2e53fb895020647
 F test/permutations.test 405542f1d659942994a6b38a9e024cf5cfd23eaa68c806aeb24a72d7c9186e80
 F test/pg_common.tcl 3b27542224db1e713ae387459b5d117c836a5f6e328846922993b6d2b7640d9f
 F test/pragma.test 11cb9310c42f921918f7f563e3c0b6e70f9f9c3a6a1cf12af8fccb6c574f3882
@@ -2211,8 +2211,8 @@ F vsixtest/vsixtest.tcl 6195aba1f12a5e10efc2b8c0009532167be5e301abe5b31385638080
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 25e68229843cc84978955817285550085d1306ba4ce3b0517dd00e5d05b9ae0a
-R 1b58d4d1990506055e066a3b56b6ff9a
+P 5d311536211eb1e3c887ceb7e6516d3900e6eebbccc8c445dd43cdd556182728
+R 8645e4703962687ea28510b503521695
 U drh
-Z 10ad6a710202821993e7562cc60a54b3
+Z c1cee7eb4fe675aa957233112b675c53
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 1413d7e77e..5c6fc432f4 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-5d311536211eb1e3c887ceb7e6516d3900e6eebbccc8c445dd43cdd556182728
+0d0e5456793b4bef673ebc7fcc1c393a6d3c817363d948ddfe06d60eab56dc24
diff --git a/test/percentile.test b/test/percentile.test
index 92c2010f4b..c2bc5633d2 100644
--- a/test/percentile.test
+++ b/test/percentile.test
@@ -287,4 +287,51 @@ SELECT a, b, c, d,
   2  B  two    7.1   F.B.E          7.1   
   5  E  two    12.5  B.E            9.8   
 }
+
+# Test case adapted from examples shown at
+# https://database.guide/3-functions-to-calculate-the-median-in-sql/
+#
+do_execsql_test percential-4.0 {
+  CREATE TABLE products(
+    vendorId INT,
+    productId INTEGER PRIMARY KEY,
+    productName REAL,
+    price REAL
+  );
+  INSERT INTO products VALUES
+    (1001, 17,  'Left-handed screwdriver', 25.99),
+    (1001, 49,  'Right-handed screwdriver', 25.99),
+    (1001, 216, 'Long weight (blue)', 14.75),
+    (1001, 31,  'Long weight (green)', 11.99),
+    (1002, 37,  'Sledge hammer', 33.49),
+    (1003, 7,   'Chainsaw', 245.00),
+    (1003, 8,   'Straw dog box', 55.99),
+    (1003, 12,  'Hammock', 11.01),
+    (1004, 113, 'Teapot', 12.45),
+    (1004, 117, 'Bottomless coffee mug', 9.99);
+}
+do_execsql_test percentile-4.1 {
+  SELECT VendorId, ProductId, /* ProductName,*/ Price,
+         avg(price) OVER (PARTITION BY vendorId) AS "Average",
+         median(price) OVER (PARTITION BY vendorId) AS "Median"
+    FROM products
+   ORDER BY vendorId, productId;
+} {
+  1001      17         25.99  19.68    20.37 
+  1001      31         11.99  19.68    20.37 
+  1001      49         25.99  19.68    20.37 
+  1001      216        14.75  19.68    20.37 
+  1002      37         33.49  33.49    33.49 
+  1003      7          245.0  104.0    55.99 
+  1003      8          55.99  104.0    55.99 
+  1003      12         11.01  104.0    55.99 
+  1004      113        12.45  11.22    11.22 
+  1004      117        9.99   11.22    11.22 
+}
+do_execsql_test percentile-4.2 {
+  SELECT vendorId, median(price) FROM products
+   GROUP BY 1 ORDER BY 1;
+} {1001 20.37 1002 33.49 1003 55.99 1004 11.22}
+
+
 finish_test

From a5315a6ecef14cd356915f7f19c0bda390d33c36 Mon Sep 17 00:00:00 2001
From: drh <>
Date: Sat, 31 Aug 2024 17:50:06 +0000
Subject: [PATCH 5/5] Still more test cases.

FossilOrigin-Name: f09904608195dac38172b0dd4dcab3190f33c116d468beff27f913a7433b400e
---
 manifest             | 12 ++++++------
 manifest.uuid        |  2 +-
 test/percentile.test | 46 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+), 7 deletions(-)

diff --git a/manifest b/manifest
index df07cca990..21b3220b47 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\smore\stest\scases.
-D 2024-08-31T17:27:55.143
+C Still\smore\stest\scases.
+D 2024-08-31T17:50:06.875
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -1517,7 +1517,7 @@ F test/parser1.test 6ccdf5e459a5dc4673d3273dc311a7e9742ca952dd0551a6a6320d27035c
 F test/pcache.test c8acbedd3b6fd0f9a7ca887a83b11d24a007972b
 F test/pcache2.test af7f3deb1a819f77a6d0d81534e97d1cf62cd442
 F test/pendingrace.test e99efc5ab3584da3dfc8cd6a0ec4e5a42214820574f5ea24ee93f1d84655f463
-F test/percentile.test 4c84880c6d5ca216206a92b6cb33c2fb27c972bec6afc6f5a2e53fb895020647
+F test/percentile.test 9ae96346c6f5f000eeeca023cabf85efefd744f7b66031147354a4da6dcb50d6
 F test/permutations.test 405542f1d659942994a6b38a9e024cf5cfd23eaa68c806aeb24a72d7c9186e80
 F test/pg_common.tcl 3b27542224db1e713ae387459b5d117c836a5f6e328846922993b6d2b7640d9f
 F test/pragma.test 11cb9310c42f921918f7f563e3c0b6e70f9f9c3a6a1cf12af8fccb6c574f3882
@@ -2211,8 +2211,8 @@ F vsixtest/vsixtest.tcl 6195aba1f12a5e10efc2b8c0009532167be5e301abe5b31385638080
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 5d311536211eb1e3c887ceb7e6516d3900e6eebbccc8c445dd43cdd556182728
-R 8645e4703962687ea28510b503521695
+P 0d0e5456793b4bef673ebc7fcc1c393a6d3c817363d948ddfe06d60eab56dc24
+R 55d55ff8a79d8904a0d256c79a96924e
 U drh
-Z c1cee7eb4fe675aa957233112b675c53
+Z 79dbcf8ff805bbacf34d3a6772c416df
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 5c6fc432f4..06468111d4 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-0d0e5456793b4bef673ebc7fcc1c393a6d3c817363d948ddfe06d60eab56dc24
+f09904608195dac38172b0dd4dcab3190f33c116d468beff27f913a7433b400e
diff --git a/test/percentile.test b/test/percentile.test
index c2bc5633d2..c7a41bbced 100644
--- a/test/percentile.test
+++ b/test/percentile.test
@@ -333,5 +333,51 @@ do_execsql_test percentile-4.2 {
    GROUP BY 1 ORDER BY 1;
 } {1001 20.37 1002 33.49 1003 55.99 1004 11.22}
 
+do_execsql_test percentile-5.0 {
+  CREATE TABLE user(name TEXT, class TEXT, cost REAL);
+  INSERT INTO user VALUES
+    ('Alice', 'Y',  3578.27),
+    ('Bob',   'X',  3399.99),
+    ('Cindy', 'Z',  699.10),
+    ('Dave',  'Y',  3078.27),
+    ('Emma',  'Z',  2319.99),
+    ('Fred',  'Y',  539.99),
+    ('Gina',  'X',  2320.49),
+    ('Hank',  'W',  24.99),
+    ('Irma',  'W',  24.99),
+    ('Jake',  'X',  2234.99),
+    ('Kim',   'Y',  4319.99),
+    ('Liam',  'X',  4968.59),
+    ('Mia',   'W',  59.53),
+    ('Nate',  'W',  23.50);
+}
+do_execsql_test percentile-5.1 {
+  SELECT name, class, cost,
+    percentile_cont(cost, 0.00) OVER w1 AS 'P0',
+    percentile_cont(cost, 0.25) OVER w1 AS 'P1',
+    percentile_cont(cost, 0.50) OVER w1 AS 'P2',
+    percentile_cont(cost, 0.75) OVER w1 AS 'P3',
+    percentile_cont(cost, 1.00) OVER w1 AS 'P4'
+  FROM user
+  WINDOW w1 AS (PARTITION BY class)
+  ORDER BY class, cost;
+} {
+  Nate   W  23.5     23.5     24.6175    24.99     33.625     59.53  
+  Hank   W  24.99    23.5     24.6175    24.99     33.625     59.53  
+  Irma   W  24.99    23.5     24.6175    24.99     33.625     59.53  
+  Mia    W  59.53    23.5     24.6175    24.99     33.625     59.53  
+  Jake   X  2234.99  2234.99  2299.115   2860.24   3792.14    4968.59
+  Gina   X  2320.49  2234.99  2299.115   2860.24   3792.14    4968.59
+  Bob    X  3399.99  2234.99  2299.115   2860.24   3792.14    4968.59
+  Liam   X  4968.59  2234.99  2299.115   2860.24   3792.14    4968.59
+  Fred   Y  539.99   539.99   2443.7     3328.27   3763.7     4319.99
+  Dave   Y  3078.27  539.99   2443.7     3328.27   3763.7     4319.99
+  Alice  Y  3578.27  539.99   2443.7     3328.27   3763.7     4319.99
+  Kim    Y  4319.99  539.99   2443.7     3328.27   3763.7     4319.99
+  Cindy  Z  699.1    699.1    1104.3225  1509.545  1914.7675  2319.99
+  Emma   Z  2319.99  699.1    1104.3225  1509.545  1914.7675  2319.99
+}
+
+
 
 finish_test