Weak interface assignment (with small performance penalty and memory use),
      corresponding to the ARC's Zeroing Weak pointers model
    - CopyObject() procedure now handle TCollection kind of object not only
      as sub properties
    - introducing TInterfacedCollection dedicated class, properly handling
      collection item creation on the Server side, with interface-based services:
      all contract operations shall use it instead of TCollection


    - added TSQLTable.FieldLengthMax() and ExpandAsSynUnicode() methods
    - added BlobToBytes() function and TSQLTable.GetBytes/GetStream methods
    - added virtual TSQLRestServer.FlushInternalDBCache method and dedicated
      TSQLRestServerStaticInMemoryExternal class, to properly handle external
      DB modification for virtual tables (i.e. flush SQL/JSON cache as expected)
    - added TSQLRestServerStatic.InternalBatchStart / InternalBatchStop methods
      to handle fast grouped sending to remote database engine (e.g. Oracle
................................................................................

    /// save the table values in JSON format
    // - JSON data is added to TStream, with UTF-8 encoding
    // - if Expand is true, JSON data is an array of objects, for direct use
    // with any Ajax or .NET client:
    // & [ {"col1":val11,"col2":"val12"},{"col1":val21,... ]
    // - if Expand is false, JSON data is serialized (used in TSQLTableJSON)
    // & { "FieldCount":1,"Values":["col1","col2",val11,"val12",val21,..] }
    // - RowFirst and RowLast can be used to ask for a specified row extent
    // of the returned data (by default, all rows are retrieved)
    procedure GetJSONValues(JSON: TStream; Expand: boolean;
      RowFirst: integer=0; RowLast: integer=0); overload;
    /// same as above, but returning result into a RawUTF8
    function GetJSONValues(Expand: boolean): RawUTF8; overload;
    /// save the table in CSV format
................................................................................

/// get the FIRST field value of the FIRST row, from a JSON content
// - e.g. usefull to get an ID without converting a JSON content into a TSQLTableJSON
function UnJSONFirstField(var P: PUTF8Char): RawUTF8;

/// returns TRUE if the JSON content is in expanded format
// - i.e. as plain [{"ID":10,"FirstName":"John","LastName":"Smith"}...]
// - i.e. not as '{"FieldCount":3,"Values":["ID","FirstName","LastName",...']}
function IsNotAjaxJSON(P: PUTF8Char): Boolean;

/// get the number of rows stored in the not-expanded JSON content
function GetRowCountNotExpanded(P: PUTF8Char; FieldCount: integer; var RowCount: integer): PUTF8Char;

/// go to the end of a field name in a JSON '"FieldName":Value' pair
// - returns nil if P was not formatted as expected
................................................................................
    (** return the UTF-8 encoded JSON objects for the values contained
      in the current published fields of a TSQLRecord child
      - only simple fields (i.e. not TSQLRawBlob/TSQLRecordMany) are retrieved:
        BLOB fields are ignored (use direct access via dedicated methods instead)
      - if Expand is true, JSON data is an object, for direct use with any Ajax or .NET client:
      ! {"col1":val11,"col2":"val12"}
      - if Expand is false, JSON data is serialized (as used in TSQLTableJSON)
      ! { "FieldCount":1,"Values":["col1","col2",val11,"val12",val21,..] }
      - if withID is true, then the first ID field value is included *)
    procedure GetJSONValues(JSON: TStream; Expand: boolean; withID: boolean;
      Occasion: TSQLOccasion); overload;
    /// same as above, but returning result into a RawUTF8
    // - if UsingStream is not set, it will use a temporary THeapMemoryStream instance
    function GetJSONValues(Expand: boolean; withID: boolean; Occasion: TSQLOccasion;
      UsingStream: TCustomMemoryStream=nil): RawUTF8; overload;
................................................................................
      inc(P);
    until false;
  end;
end;

function UnJSONFirstField(var P: PUTF8Char): RawUTF8;
// expand=true: [ {"col1":val11} ] -> val11
// expand=false: { "FieldCount":1,"Values":["col1",val11] } -> vall11
begin
  result := '';
  if P=nil then exit;
  if Expect(P,'{"FieldCount":') then begin
    // not expanded format
    if GetJSONIntegerVar(P)<>1 then
      exit; // wrong field count
    while P^<>'[' do if P^=#0 then exit else inc(P); // go to ["col1"
    inc(P); // go to "col1"
  end else begin
    // expanded format
................................................................................
  end;
  GetJSONField(P,P); // ignore field name
  result := GetJSONField(P,P); // get field value
end;

function IsNotAjaxJSON(P: PUTF8Char): Boolean;
begin
  result := Expect(P,'{"FieldCount":');
end;

function IsNotExpanded(var P: PUTF8Char; var FieldCount: integer): boolean;
begin
  if not IsNotAjaxJSON(P) then begin
    result := false;
    exit;
  end;
  inc(P,14);
  FieldCount := GetJSONIntegerVar(P);
  result := (FieldCount<>0) and Expect(P,',"Values":[');
end;

function GetRowCountNotExpanded(P: PUTF8Char; FieldCount: integer; var RowCount: integer): PUTF8Char;
begin
  RowCount := 0;
  result := P; // no data at all of unexpected end
  repeat
................................................................................
  result := false; // error on parsing
  if (self=nil) or (Buffer=nil) then
    exit;
  // go to start of object
  P := GotoNextNotSpace(Buffer);
  if IsNotExpanded(P,fFieldCount) then begin
    // A. Not Expanded format
(* {"FieldCount":9,"Values":["ID","Int","Test","Unicode","Ansi","ValFloat","ValWord",
    "ValDate","Next",0,0,"abcde+�ef+�+�","abcde+�ef+�+�","abcde+�ef+�+�",
    3.14159265300000E+0000,1203,"2009-03-10T21:19:36",0,..]} *)
    // 1. get RowCount and DataLen
    DataLen := GetRowCountNotExpanded(P,FieldCount,fRowCount)-P; // also check P^ format
    if DataLen=0 then begin
      fRowCount := 0;
      exit;
................................................................................
      Freemem(tmp);
    end;
  end;
end;

procedure TSQLRecord.FillFrom(P: PUTF8Char);
(* two possible formats = first not expanded, 2nd is expanded (most usefull)
 {"FieldCount":9,"Values":["ID","Int","Test","Unicode","Ansi","ValFloat","ValWord",
  "ValDate","Next",0,0,"abcde+�ef+�+�","abcde+�ef+�+�","abcde+�ef+�+�",
  3.14159265300000E+0000,1203,"2009-03-10T21:19:36",0]}
 {"ID":0,"Int":0,"Test":"abcde+�ef+�+�","Unicode":"abcde+�ef+�+�","Ansi":
 "abcde+�ef+�+�","ValFloat": 3.14159265300000E+0000,"ValWord":1203,
 "ValDate":"2009-03-10T21:19:36","Next":0} *)
var F: array[0..MAX_SQLFIELDS-1] of PUTF8Char; // store field/property names
    i, n: integer;
................................................................................
    Value: PUTF8Char;
begin
  // go to start of object
  if P=nil then
    exit;
  while P^<>'{' do
    if P^=#0 then exit else inc(P);
  if Expect(P,'{"FieldCount":') then begin
    // not expanded format
    n := GetJSONIntegerVar(P)-1;
    if (cardinal(n)>high(F)) or not Expect(P,',"Values":[') then
      exit;
    for i := 0 to n do
      F[i] := GetJSONField(P,P); // get field names
    for i := 0 to n do begin
      Prop := F[i]; // share shortstring on stack with code below
      FillValue(Prop,GetJSONField(P,P)); // set properties from values
    end;
................................................................................
procedure TSQLModel.SetTableProps(aTable: TSQLRecordClass; aIndex: integer;
  Last, VirtualsRemain: boolean);
var f, R: integer;
    Props: TSQLRecordProperties;
    PT: PTypeInfo;
begin
  Props := aTable.RecordProps;
  if not VirtualsRemain then
    Props.Kind := rSQLite3; // reset to internal table at model creation
  if Props.Model=nil then begin
    Props.Model := self;
    Props.ModelTableIndex := aIndex;
  end;
  TableProps[aIndex] := Props;
  fTablesName[aIndex] := Props.SQLTableName;
................................................................................
        W.Add(',');
      end;
      result := fValue.Count;
    end else
      result := FindWhereEqual(WhereField,WhereValue,GetJSONValuesEvent,W);
    if (result=0) and W.Expand then begin
      // we want the field names at least, even with no data
      Expand := false; //  {"FieldCount":2,"Values":["col1","col2"]}
      W.Expand := false;
      W.CancelAll;
      fStoredClassProps.SetJSONWriterColumnNames(W);
    end;
    W.CancelLastComma; // cancel last ','
    // end the JSON object
    W.Add(']');

      Weak interface assignment (with small performance penalty and memory use),
      corresponding to the ARC's Zeroing Weak pointers model
    - CopyObject() procedure now handle TCollection kind of object not only
      as sub properties
    - introducing TInterfacedCollection dedicated class, properly handling
      collection item creation on the Server side, with interface-based services:
      all contract operations shall use it instead of TCollection
    - changed the non expanded JSON format to use lowercase first column names:
      {"fieldCount":1,"values":["col1"... instead of {"FieldCount":1,"Values":[..
    - added TSQLTable.FieldLengthMax() and ExpandAsSynUnicode() methods
    - added BlobToBytes() function and TSQLTable.GetBytes/GetStream methods
    - added virtual TSQLRestServer.FlushInternalDBCache method and dedicated
      TSQLRestServerStaticInMemoryExternal class, to properly handle external
      DB modification for virtual tables (i.e. flush SQL/JSON cache as expected)
    - added TSQLRestServerStatic.InternalBatchStart / InternalBatchStop methods
      to handle fast grouped sending to remote database engine (e.g. Oracle
................................................................................

    /// save the table values in JSON format
    // - JSON data is added to TStream, with UTF-8 encoding
    // - if Expand is true, JSON data is an array of objects, for direct use
    // with any Ajax or .NET client:
    // & [ {"col1":val11,"col2":"val12"},{"col1":val21,... ]
    // - if Expand is false, JSON data is serialized (used in TSQLTableJSON)
    // & { "fieldCount":1,"values":["col1","col2",val11,"val12",val21,..] }
    // - RowFirst and RowLast can be used to ask for a specified row extent
    // of the returned data (by default, all rows are retrieved)
    procedure GetJSONValues(JSON: TStream; Expand: boolean;
      RowFirst: integer=0; RowLast: integer=0); overload;
    /// same as above, but returning result into a RawUTF8
    function GetJSONValues(Expand: boolean): RawUTF8; overload;
    /// save the table in CSV format
................................................................................

/// get the FIRST field value of the FIRST row, from a JSON content
// - e.g. usefull to get an ID without converting a JSON content into a TSQLTableJSON
function UnJSONFirstField(var P: PUTF8Char): RawUTF8;

/// returns TRUE if the JSON content is in expanded format
// - i.e. as plain [{"ID":10,"FirstName":"John","LastName":"Smith"}...]
// - i.e. not as '{"fieldCount":3,"values":["ID","FirstName","LastName",...']}
function IsNotAjaxJSON(P: PUTF8Char): Boolean;

/// get the number of rows stored in the not-expanded JSON content
function GetRowCountNotExpanded(P: PUTF8Char; FieldCount: integer; var RowCount: integer): PUTF8Char;

/// go to the end of a field name in a JSON '"FieldName":Value' pair
// - returns nil if P was not formatted as expected
................................................................................
    (** return the UTF-8 encoded JSON objects for the values contained
      in the current published fields of a TSQLRecord child
      - only simple fields (i.e. not TSQLRawBlob/TSQLRecordMany) are retrieved:
        BLOB fields are ignored (use direct access via dedicated methods instead)
      - if Expand is true, JSON data is an object, for direct use with any Ajax or .NET client:
      ! {"col1":val11,"col2":"val12"}
      - if Expand is false, JSON data is serialized (as used in TSQLTableJSON)
      ! { "fieldCount":1,"values":["col1","col2",val11,"val12",val21,..] }
      - if withID is true, then the first ID field value is included *)
    procedure GetJSONValues(JSON: TStream; Expand: boolean; withID: boolean;
      Occasion: TSQLOccasion); overload;
    /// same as above, but returning result into a RawUTF8
    // - if UsingStream is not set, it will use a temporary THeapMemoryStream instance
    function GetJSONValues(Expand: boolean; withID: boolean; Occasion: TSQLOccasion;
      UsingStream: TCustomMemoryStream=nil): RawUTF8; overload;
................................................................................
      inc(P);
    until false;
  end;
end;

function UnJSONFirstField(var P: PUTF8Char): RawUTF8;
// expand=true: [ {"col1":val11} ] -> val11
// expand=false: { "fieldCount":1,"values":["col1",val11] } -> vall11
begin
  result := '';
  if P=nil then exit;
  if Expect(P,'{"fieldCount":') then begin
    // not expanded format
    if GetJSONIntegerVar(P)<>1 then
      exit; // wrong field count
    while P^<>'[' do if P^=#0 then exit else inc(P); // go to ["col1"
    inc(P); // go to "col1"
  end else begin
    // expanded format
................................................................................
  end;
  GetJSONField(P,P); // ignore field name
  result := GetJSONField(P,P); // get field value
end;

function IsNotAjaxJSON(P: PUTF8Char): Boolean;
begin
  result := Expect(P,'{"fieldCount":');
end;

function IsNotExpanded(var P: PUTF8Char; var FieldCount: integer): boolean;
begin
  if not IsNotAjaxJSON(P) then begin
    result := false;
    exit;
  end;
  inc(P,14);
  FieldCount := GetJSONIntegerVar(P);
  result := (FieldCount<>0) and Expect(P,',"values":[');
end;

function GetRowCountNotExpanded(P: PUTF8Char; FieldCount: integer; var RowCount: integer): PUTF8Char;
begin
  RowCount := 0;
  result := P; // no data at all of unexpected end
  repeat
................................................................................
  result := false; // error on parsing
  if (self=nil) or (Buffer=nil) then
    exit;
  // go to start of object
  P := GotoNextNotSpace(Buffer);
  if IsNotExpanded(P,fFieldCount) then begin
    // A. Not Expanded format
(* {"fieldCount":9,"values":["ID","Int","Test","Unicode","Ansi","ValFloat","ValWord",
    "ValDate","Next",0,0,"abcde+�ef+�+�","abcde+�ef+�+�","abcde+�ef+�+�",
    3.14159265300000E+0000,1203,"2009-03-10T21:19:36",0,..]} *)
    // 1. get RowCount and DataLen
    DataLen := GetRowCountNotExpanded(P,FieldCount,fRowCount)-P; // also check P^ format
    if DataLen=0 then begin
      fRowCount := 0;
      exit;
................................................................................
      Freemem(tmp);
    end;
  end;
end;

procedure TSQLRecord.FillFrom(P: PUTF8Char);
(* two possible formats = first not expanded, 2nd is expanded (most usefull)
 {"fieldCount":9,"values":["ID","Int","Test","Unicode","Ansi","ValFloat","ValWord",
  "ValDate","Next",0,0,"abcde+�ef+�+�","abcde+�ef+�+�","abcde+�ef+�+�",
  3.14159265300000E+0000,1203,"2009-03-10T21:19:36",0]}
 {"ID":0,"Int":0,"Test":"abcde+�ef+�+�","Unicode":"abcde+�ef+�+�","Ansi":
 "abcde+�ef+�+�","ValFloat": 3.14159265300000E+0000,"ValWord":1203,
 "ValDate":"2009-03-10T21:19:36","Next":0} *)
var F: array[0..MAX_SQLFIELDS-1] of PUTF8Char; // store field/property names
    i, n: integer;
................................................................................
    Value: PUTF8Char;
begin
  // go to start of object
  if P=nil then
    exit;
  while P^<>'{' do
    if P^=#0 then exit else inc(P);
  if Expect(P,'{"fieldCount":') then begin
    // not expanded format
    n := GetJSONIntegerVar(P)-1;
    if (cardinal(n)>high(F)) or not Expect(P,',"values":[') then
      exit;
    for i := 0 to n do
      F[i] := GetJSONField(P,P); // get field names
    for i := 0 to n do begin
      Prop := F[i]; // share shortstring on stack with code below
      FillValue(Prop,GetJSONField(P,P)); // set properties from values
    end;
................................................................................
procedure TSQLModel.SetTableProps(aTable: TSQLRecordClass; aIndex: integer;
  Last, VirtualsRemain: boolean);
var f, R: integer;
    Props: TSQLRecordProperties;
    PT: PTypeInfo;
begin
  Props := aTable.RecordProps;
  if (not VirtualsRemain) and (Props.Kind in IS_CUSTOM_VIRTUAL) then
    Props.Kind := rSQLite3; // reset to internal table at model creation
  if Props.Model=nil then begin
    Props.Model := self;
    Props.ModelTableIndex := aIndex;
  end;
  TableProps[aIndex] := Props;
  fTablesName[aIndex] := Props.SQLTableName;
................................................................................
        W.Add(',');
      end;
      result := fValue.Count;
    end else
      result := FindWhereEqual(WhereField,WhereValue,GetJSONValuesEvent,W);
    if (result=0) and W.Expand then begin
      // we want the field names at least, even with no data
      Expand := false; //  {"fieldCount":2,"values":["col1","col2"]}
      W.Expand := false;
      W.CancelAll;
      fStoredClassProps.SetJSONWriterColumnNames(W);
    end;
    W.CancelLastComma; // cancel last ','
    // end the JSON object
    W.Add(']');

    TObjectListPropertyHashed class, which allows hashing of a sub-property
    of an object (including some changes made to TDynArray/TDynArrayHshed)
  - new TTextWriter.AddDateTime() overloaded method able to quote the output
  - both TTextWriter.AddDateTime() overloaded methods will store '' when value
    is 0, or a pure ISO-8601 date or time if the value is defined as such,
    just as expected by http://www.sqlite.org/lang_datefunc.html - it will also
    reduce average generated JSON/text content size


  - new SetInt64() procedure for direct assignment of the result
  - TSynTableStatement class now accepts '_' in table and column identifiers
  - fixed implementation issue in function FindNextUTF8WordBegin()
  - fixed false negative issue in TSynSoundEx.UTF8 and TSynSoundEx.Ansi
  - added an optional parameter to StrToCurr64() function, able to return
    a true Int64 value if no decimal is supplied within the input text buffer
  - enhanced TSynAnsiFixedWidth.UnicodeBufferToAnsi average process speed
................................................................................
    /// used to store output format for TSQLRecord.GetJSONValues()
    fWithID: boolean;
    /// used to store field for TSQLRecord.GetJSONValues()
    fFields: TSQLFieldBits;
    fFieldMax: integer;
    /// if not Expanded format, contains the Stream position of the first
    // usefull Row of data; i.e. ',val11' position in:
    // & { "FieldCount":1,"Values":["col1","col2",val11,"val12",val21,..] }
    fStartDataPosition: integer;
  public
    /// used internally to store column names and count for AddColumns
    ColNames: TRawUTF8DynArray;
    /// the data will be written to the specified Stream
    // - if no Stream is supplied, a temporary memory stream will be created
    // (it's faster to supply one, e.g. any TSQLRest.TempMemoryStream)
................................................................................
    /// Read-Only access to the field bits set for each column to be stored
    property Fields: TSQLFieldBits read fFields write fFields;
    /// Read-Only access to the higher field index to be stored
    // - i.e. the highest bit set in Fields
    property FieldMax: integer read fFieldMax write fFieldMax;
    /// if not Expanded format, contains the Stream position of the first
    // usefull Row of data; i.e. ',val11' position in:
    // & { "FieldCount":1,"Values":["col1","col2",val11,"val12",val21,..] }
    property StartDataPosition: integer read fStartDataPosition;
  end;

  /// implement a cache of some key/value pairs, e.g. to improve reading speed
  // - used e.g. by TSQLDataBase for caching the SELECT statements results in an
  // internal JSON format (which is faster than a query to the SQLite3 engine)
  // - internally make use of an efficient hashing algorithm for fast response
................................................................................
      const Fields: TSQLFieldBits): TJSONWriter;
    (** return the UTF-8 encoded JSON objects for the values contained
      in the specified RecordBuffer encoded in our SBF compact binary format,
      according to the Expand/WithID/Fields parameters of W
      - if W.Expand is true, JSON data is an object, for direct use with any Ajax or .NET client:
      ! {"col1":val11,"col2":"val12"}
      - if W.Expand is false, JSON data is serialized (as used in TSQLTableJSON)
      ! { "FieldCount":1,"Values":["col1","col2",val11,"val12",val21,..] }
      - only fields with a bit set in W.Fields will be appended
      - if W.WithID is true, then the first ID field value is included *)
    procedure GetJSONValues(aID: integer; RecordBuffer: PUTF8Char; W: TJSONWriter);
    /// can be used to retrieve all values matching a preparated TSynTableStatement
    // - this method matchs the TSynBigTableIterateEvent callback definition
    // - Sender will be the TSynBigTable instance, and Opaque will point to a
    // TSynTableStatement instance (with all fields initialized, including Writer)
................................................................................
procedure TJSONWriter.AddColumns;
var i: integer;
begin
  if fExpand then begin
    for i := 0 to High(ColNames) do
      ColNames[i] := '"'+ColNames[i]+'":';
  end else begin
    AddShort('{"FieldCount":');
    Add(length(ColNames));
    AddShort(',"Values":["');
    // first row is FieldNames
    for i := 0 to High(ColNames) do begin
      AddString(ColNames[i]);
      AddNoJSONEscape(PAnsiChar('","'),3);
    end;
    CancelLastChar; // cancel last '"'
    fStartDataPosition := fStream.Position+(B-fTempBuf);
     // B := buf-1 at startup -> need ',val11' position in
     // 'Values":["col1","col2",val11,' i.e. current pos without the ','
  end;
end;

procedure TJSONWriter.TrimFirstRow;
var P, PBegin, PEnd: PUTF8Char;
begin
  if (self=nil) or not fStream.InheritsFrom(TMemoryStream) or
     fExpand or (fStartDataPosition=0) then
    exit;
  // go to begin of first row
  Flush; // we need the data to be in fStream memory
  // PBegin^=val11 in { "FieldCount":1,"Values":["col1","col2",val11,"val12",val21,..] }
  PBegin := TMemoryStream(fStream).Memory;
  PEnd := PBegin+fStream.Position;
  PEnd^ := #0; // mark end of current values
  inc(PBegin,fStartDataPosition+1); // +1 to include ',' of ',val11'
  // jump to end of first row
  P := GotoNextJSONField(PBegin,length(ColNames));
  if P=nil then exit; // unexpected end

    TObjectListPropertyHashed class, which allows hashing of a sub-property
    of an object (including some changes made to TDynArray/TDynArrayHshed)
  - new TTextWriter.AddDateTime() overloaded method able to quote the output
  - both TTextWriter.AddDateTime() overloaded methods will store '' when value
    is 0, or a pure ISO-8601 date or time if the value is defined as such,
    just as expected by http://www.sqlite.org/lang_datefunc.html - it will also
    reduce average generated JSON/text content size
  - changed the non expanded JSON format to use lowercase first column names:
    {"fieldCount":1,"values":["col1"... instead of {"FieldCount":1,"Values":[..
  - new SetInt64() procedure for direct assignment of the result
  - TSynTableStatement class now accepts '_' in table and column identifiers
  - fixed implementation issue in function FindNextUTF8WordBegin()
  - fixed false negative issue in TSynSoundEx.UTF8 and TSynSoundEx.Ansi
  - added an optional parameter to StrToCurr64() function, able to return
    a true Int64 value if no decimal is supplied within the input text buffer
  - enhanced TSynAnsiFixedWidth.UnicodeBufferToAnsi average process speed
................................................................................
    /// used to store output format for TSQLRecord.GetJSONValues()
    fWithID: boolean;
    /// used to store field for TSQLRecord.GetJSONValues()
    fFields: TSQLFieldBits;
    fFieldMax: integer;
    /// if not Expanded format, contains the Stream position of the first
    // usefull Row of data; i.e. ',val11' position in:
    // & { "fieldCount":1,"values":["col1","col2",val11,"val12",val21,..] }
    fStartDataPosition: integer;
  public
    /// used internally to store column names and count for AddColumns
    ColNames: TRawUTF8DynArray;
    /// the data will be written to the specified Stream
    // - if no Stream is supplied, a temporary memory stream will be created
    // (it's faster to supply one, e.g. any TSQLRest.TempMemoryStream)
................................................................................
    /// Read-Only access to the field bits set for each column to be stored
    property Fields: TSQLFieldBits read fFields write fFields;
    /// Read-Only access to the higher field index to be stored
    // - i.e. the highest bit set in Fields
    property FieldMax: integer read fFieldMax write fFieldMax;
    /// if not Expanded format, contains the Stream position of the first
    // usefull Row of data; i.e. ',val11' position in:
    // & { "fieldCount":1,"values":["col1","col2",val11,"val12",val21,..] }
    property StartDataPosition: integer read fStartDataPosition;
  end;

  /// implement a cache of some key/value pairs, e.g. to improve reading speed
  // - used e.g. by TSQLDataBase for caching the SELECT statements results in an
  // internal JSON format (which is faster than a query to the SQLite3 engine)
  // - internally make use of an efficient hashing algorithm for fast response
................................................................................
      const Fields: TSQLFieldBits): TJSONWriter;
    (** return the UTF-8 encoded JSON objects for the values contained
      in the specified RecordBuffer encoded in our SBF compact binary format,
      according to the Expand/WithID/Fields parameters of W
      - if W.Expand is true, JSON data is an object, for direct use with any Ajax or .NET client:
      ! {"col1":val11,"col2":"val12"}
      - if W.Expand is false, JSON data is serialized (as used in TSQLTableJSON)
      ! { "fieldCount":1,"values":["col1","col2",val11,"val12",val21,..] }
      - only fields with a bit set in W.Fields will be appended
      - if W.WithID is true, then the first ID field value is included *)
    procedure GetJSONValues(aID: integer; RecordBuffer: PUTF8Char; W: TJSONWriter);
    /// can be used to retrieve all values matching a preparated TSynTableStatement
    // - this method matchs the TSynBigTableIterateEvent callback definition
    // - Sender will be the TSynBigTable instance, and Opaque will point to a
    // TSynTableStatement instance (with all fields initialized, including Writer)
................................................................................
procedure TJSONWriter.AddColumns;
var i: integer;
begin
  if fExpand then begin
    for i := 0 to High(ColNames) do
      ColNames[i] := '"'+ColNames[i]+'":';
  end else begin
    AddShort('{"fieldCount":');
    Add(length(ColNames));
    AddShort(',"values":["');
    // first row is FieldNames
    for i := 0 to High(ColNames) do begin
      AddString(ColNames[i]);
      AddNoJSONEscape(PAnsiChar('","'),3);
    end;
    CancelLastChar; // cancel last '"'
    fStartDataPosition := fStream.Position+(B-fTempBuf);
     // B := buf-1 at startup -> need ',val11' position in
     // "values":["col1","col2",val11,' i.e. current pos without the ','
  end;
end;

procedure TJSONWriter.TrimFirstRow;
var P, PBegin, PEnd: PUTF8Char;
begin
  if (self=nil) or not fStream.InheritsFrom(TMemoryStream) or
     fExpand or (fStartDataPosition=0) then
    exit;
  // go to begin of first row
  Flush; // we need the data to be in fStream memory
  // PBegin^=val11 in { "fieldCount":1,"values":["col1","col2",val11,"val12",val21,..] }
  PBegin := TMemoryStream(fStream).Memory;
  PEnd := PBegin+fStream.Position;
  PEnd^ := #0; // mark end of current values
  inc(PBegin,fStartDataPosition+1); // +1 to include ',' of ',val11'
  // jump to end of first row
  P := GotoNextJSONField(PBegin,length(ColNames));
  if P=nil then exit; // unexpected end