Get writes working on the sqlite_dbpage virtual table. Add a few test cases.

FossilOrigin-Name: a8b264d811e5bcb7e3ae8a12bf5b6830a9d1adff1f59436dda9e886f97da242f

manifest

@@ -1,5 +1,5 @@
-C Initial\simplementation\sof\sthe\s"sqlite_dbpage"\svirtual\stable.\s\sCurrently\nit\sis\sread-only\sand\shas\sa\splace-holder\sxBestIndex.
+C Get\swrites\sworking\son\sthe\ssqlite_dbpage\svirtual\stable.\s\sAdd\sa\sfew\stest\scases.
-D 2017-10-11T13:48:11.877
+D 2017-10-11T15:02:53.047
 F Makefile.in f7cba589198b8663d8a43f25ad001cf44fdac4fcd6216325f05775924a7af2f9
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 1224c8773fc7f89c57e83c7b452291d239aa2cff4af50a204c84129e295cc37d
@@ -409,7 +409,7 @@ F src/callback.c 28a8ede982fde4129b828350f78f2c01fe7d12c74d1a0a05d7108ab36f30868
 F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
 F src/ctime.c ff1be3eed7bdd75aaca61ca8dc848f7c9f850ef2fb9cb56f2734e922a098f9c0
 F src/date.c 48f743d88bbe88f848532d333cca84f26e52a4f217e86f86be7fc1b919c33d74
-F src/dbpage.c f274a9b7bb680cc2952ee78883d67e133be0ef6065317813586a5f723af35ad5
+F src/dbpage.c c625a0bd605d4cea9a3258b8db49a5474a04976e95a9fe380cdaf74e8eb6736d
 F src/dbstat.c 7a4ba8518b6369ef3600c49cf9c918ad979acba610b2aebef1b656d649b96720
 F src/delete.c 21a5f1812fdb599e9f7afb9f650bdabab60a3afd51d7e94e539c982f647b0023
 F src/expr.c 4d2d0aafd945424f638ee03e11330f03288ccf616e025498f3c8602d01609a0a
@@ -709,6 +709,7 @@ F test/cursorhint2.test 8457e93d97f665f23f97cdbc8477d16e3480331b
 F test/date.test 9b73bbeb1b82d9c1f44dec5cf563bf7da58d2373
 F test/date2.test 74c234bece1b016e94dd4ef9c8cc7a199a8806c0e2291cab7ba64bace6350b10
 F test/dbfuzz.c 73047c920d6210e5912c87cdffd9a1c281d4252e
+F test/dbpage.test 9cf4dc92a4de67c81e5c32b24e3fbb8c4757e4b642694a219b3090a4f9277a4d
 F test/dbstatus.test 73149851b3aff14fc6db478e58f9083a66422cf5
 F test/dbstatus2.test e93ab03bfae6d62d4d935f20de928c19ca0ed0ab
 F test/default.test 0cb49b1c315a0d81c81d775e407f66906a2a604d
@@ -1657,10 +1658,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 0245adffc6f9b580217e0d2feb396d6895e54cdc25f5dfc9c8f4090b919e9e49
+P c2c1d656e3f52465192c2a697a976cd1837ccc4e10708a2377cff8bf6eaa7d49
-R 9d91f38d6de2e0aabd371a2c4dbcd832
+R 92490bca397034b7f3fba4e951f0781d
-T *branch * dbpage
-T *sym-dbpage *
-T -sym-trunk *
 U drh
-Z 95e75b385006fb35e51e104eb16c88ba
+Z ddf133cf759c24442aeeb91134927fef

manifest.uuid

@@ -1 +1 @@
-c2c1d656e3f52465192c2a697a976cd1837ccc4e10708a2377cff8bf6eaa7d49
+a8b264d811e5bcb7e3ae8a12bf5b6830a9d1adff1f59436dda9e886f97da242f

src/dbpage.c

@@ -16,6 +16,19 @@
 ** pages of the database file.  The pager interface is used so that 
 ** uncommitted changes and changes recorded in the WAL file are correctly
 ** retrieved.
+**
+** Usage example:
+**
+**    SELECT data FROM sqlite_dbpage('aux1') WHERE pgno=123;
+**
+** This is an eponymous virtual table so it does not need to be created before
+** use.  The optional argument to the sqlite_dbpage() table name is the
+** schema for the database file that is to be read.  The default schema is
+** "main".
+**
+** The data field of sqlite_dbpage table can be updated.  The new
+** value must be a BLOB which is the correct page size, otherwise the
+** update fails.  Rows may not be deleted or inserted.
 */
 
 #include "sqliteInt.h"   /* Requires access to internal data structures */
@@ -28,6 +41,7 @@ typedef struct DbpageCursor DbpageCursor;
 struct DbpageCursor {
   sqlite3_vtab_cursor base;       /* Base class.  Must be first */
   int pgno;                       /* Current page number */
+  int mxPgno;                     /* Last page to visit on this scan */
 };
 
 struct DbpageTable {
@@ -65,7 +79,7 @@ static int dbpageConnect(
     iDb = 0;
   }
   rc = sqlite3_declare_vtab(db, 
-          "CREATE TABLE x(pgno INTEGER PRIMARY KEY, data BLOB)");
+          "CREATE TABLE x(pgno INTEGER PRIMARY KEY, data BLOB, schema HIDDEN)");
   if( rc==SQLITE_OK ){
     pTab = (DbpageTable *)sqlite3_malloc64(sizeof(DbpageTable));
     if( pTab==0 ) rc = SQLITE_NOMEM_BKPT;
@@ -99,7 +113,26 @@ static int dbpageDisconnect(sqlite3_vtab *pVtab){
 **     1     pgno=?1
 */
 static int dbpageBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  int i;
   pIdxInfo->estimatedCost = 1.0e6;  /* Initial cost estimate */
+  for(i=0; i<pIdxInfo->nConstraint; i++){
+    struct sqlite3_index_constraint *p = &pIdxInfo->aConstraint[i];
+    if( p->usable && p->iColumn<=0 && p->op==SQLITE_INDEX_CONSTRAINT_EQ ){
+      pIdxInfo->estimatedRows = 1;
+      pIdxInfo->idxFlags = SQLITE_INDEX_SCAN_UNIQUE;
+      pIdxInfo->estimatedCost = 1.0;
+      pIdxInfo->idxNum = 1;
+      pIdxInfo->aConstraintUsage[i].argvIndex = 1;
+      pIdxInfo->aConstraintUsage[i].omit = 1;
+      break;
+    }
+  }
+  if( pIdxInfo->nOrderBy>=1
+   && pIdxInfo->aOrderBy[0].iColumn<=0
+   && pIdxInfo->aOrderBy[0].desc==0
+  ){
+    pIdxInfo->orderByConsumed = 1;
+  }
   return SQLITE_OK;
 }
 
@@ -143,8 +176,7 @@ static int dbpageNext(sqlite3_vtab_cursor *pCursor){
 
 static int dbpageEof(sqlite3_vtab_cursor *pCursor){
   DbpageCursor *pCsr = (DbpageCursor *)pCursor;
-  DbpageTable *pTab = (DbpageTable *)pCursor->pVtab;
+  return pCsr->pgno > pCsr->mxPgno;
-  return pCsr->pgno >= pTab->nPage;
 }
 
 static int dbpageFilter(
@@ -157,13 +189,20 @@ static int dbpageFilter(
   int rc = SQLITE_OK;
   Btree *pBt = pTab->db->aDb[pTab->iDb].pBt;
 
-  if( idxNum==1 ){
-    pCsr->pgno = sqlite3_value_int(argv[0]);
-  }else{
-    pCsr->pgno = 0;
-  }
   pTab->szPage = sqlite3BtreeGetPageSize(pBt);
   pTab->nPage = sqlite3BtreeLastPage(pBt);
+  if( idxNum==1 ){
+    pCsr->pgno = sqlite3_value_int(argv[0]);
+    if( pCsr->pgno<1 || pCsr->pgno>pTab->nPage ){
+      pCsr->pgno = 1;
+      pCsr->mxPgno = 0;
+    }else{
+      pCsr->mxPgno = pCsr->pgno;
+    }
+  }else{
+    pCsr->pgno = 1;
+    pCsr->mxPgno = pTab->nPage;
+  }
   return rc;
 }
 
@@ -205,6 +244,55 @@ static int dbpageRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
   return SQLITE_OK;
 }
 
+static int dbpageUpdate(
+  sqlite3_vtab *pVtab,
+  int argc,
+  sqlite3_value **argv,
+  sqlite_int64 *pRowid
+){
+  DbpageTable *pTab = (DbpageTable *)pVtab;
+  int pgno;
+  DbPage *pDbPage = 0;
+  int rc = SQLITE_OK;
+  char *zErr = 0;
+
+  if( argc==1 ){
+    zErr = "cannot delete";
+    goto update_fail;
+  }
+  pgno = sqlite3_value_int(argv[0]);
+  if( pgno<1 || pgno>pTab->nPage ){
+    zErr = "bad page number";
+    goto update_fail;
+  }
+  if( sqlite3_value_int(argv[1])!=pgno ){
+    zErr = "cannot insert";
+    goto update_fail;
+  }
+  if( sqlite3_value_type(argv[3])!=SQLITE_BLOB 
+   || sqlite3_value_bytes(argv[3])!=pTab->szPage 
+  ){
+    zErr = "bad page value";
+    goto update_fail;
+  }
+  rc = sqlite3PagerGet(pTab->pPager, pgno, (DbPage**)&pDbPage, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3PagerWrite(pDbPage);
+    if( rc==SQLITE_OK ){
+      memcpy(sqlite3PagerGetData(pDbPage),
+             sqlite3_value_blob(argv[3]),
+             pTab->szPage);
+    }
+  }
+  sqlite3PagerUnref(pDbPage);
+  return rc;
+
+update_fail:
+  sqlite3_free(pVtab->zErrMsg);
+  pVtab->zErrMsg = sqlite3_mprintf("%s", zErr);
+  return SQLITE_ERROR;
+}
+
 /*
 ** Invoke this routine to register the "dbpage" virtual table module
 */
@@ -223,7 +311,7 @@ int sqlite3DbpageRegister(sqlite3 *db){
     dbpageEof,                    /* xEof - check for end of scan */
     dbpageColumn,                 /* xColumn - read data */
     dbpageRowid,                  /* xRowid - read data */
-    0,                            /* xUpdate */
+    dbpageUpdate,                 /* xUpdate */
     0,                            /* xBegin */
     0,                            /* xSync */
     0,                            /* xCommit */

test/dbpage.test

@@ -0,0 +1,69 @@
+# 2017-10-11
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+# This file implements regression tests for SQLite library.  The
+# focus of this file is testing the sqlite_dbpage virtual table.
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix dbpage
+
+ifcapable !vtab||!compound {
+  finish_test
+  return
+}
+
+do_execsql_test 100 {
+  PRAGMA page_size=4096;
+  PRAGMA journal_mode=WAL;
+  CREATE TABLE t1(a,b);
+  WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<100)
+  INSERT INTO t1(a,b) SELECT x, printf('%d-x%.*c',x,x,'x') FROM c;
+  PRAGMA integrity_check;
+} {wal ok}
+do_execsql_test 110 {
+  SELECT pgno, quote(substr(data,1,5)) FROM sqlite_dbpage('main') ORDER BY pgno;
+} {1 X'53514C6974' 2 X'0500000001' 3 X'0D0000004E' 4 X'0D00000016'}
+do_execsql_test 120 {
+  SELECT pgno, quote(substr(data,1,5)) FROM sqlite_dbpage WHERE pgno=2;
+} {2 X'0500000001'}
+do_execsql_test 130 {
+  SELECT pgno, quote(substr(data,1,5)) FROM sqlite_dbpage WHERE pgno=4;
+} {4 X'0D00000016'}
+do_execsql_test 140 {
+  SELECT pgno, quote(substr(data,1,5)) FROM sqlite_dbpage WHERE pgno=5;
+} {}
+do_execsql_test 150 {
+  SELECT pgno, quote(substr(data,1,5)) FROM sqlite_dbpage WHERE pgno=0;
+} {}
+
+do_execsql_test 200 {
+  CREATE TEMP TABLE saved_content(x);
+  INSERT INTO saved_content(x) SELECT data FROM sqlite_dbpage WHERE pgno=4;
+  UPDATE sqlite_dbpage SET data=zeroblob(4096) WHERE pgno=4;
+} {}
+do_catchsql_test 210 {
+  PRAGMA integrity_check;
+} {1 {database disk image is malformed}}
+do_execsql_test 220 {
+  SELECT pgno, quote(substr(data,1,5)) FROM sqlite_dbpage('main') ORDER BY pgno;
+} {1 X'53514C6974' 2 X'0500000001' 3 X'0D0000004E' 4 X'0000000000'}
+do_execsql_test 230 {
+  UPDATE sqlite_dbpage SET data=(SELECT x FROM saved_content) WHERE pgno=4;
+} {}
+do_catchsql_test 230 {
+  PRAGMA integrity_check;
+} {0 ok}
+
+
+
+
+finish_test