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Commitbd8d441

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Second round of FE/BE protocol changes. Frontend->backend messages now
have length counts, and COPY IN data is packetized into messages.
1 parent54b38d2 commitbd8d441

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24 files changed

+1321
-966
lines changed

24 files changed

+1321
-966
lines changed

‎doc/src/sgml/libpq.sgml

Lines changed: 5 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/libpq.sgml,v 1.118 2003/04/17 22:26:00 tgl Exp $
2+
$Header: /cvsroot/pgsql/doc/src/sgml/libpq.sgml,v 1.119 2003/04/19 00:02:29 tgl Exp $
33
-->
44

55
<chapter id="libpq">
@@ -1749,9 +1749,10 @@ state will never end.
17491749
<term><function>PQflush</function></term>
17501750
<listitem>
17511751
<para>
1752-
Attempts to flush any data queued to the server,
1753-
returns 0 if successful (or if the send queue is empty) or <symbol>EOF</symbol> if it failed for
1754-
some reason.
1752+
Attempts to flush any data queued to the server.
1753+
Returns 0 if successful (or if the send queue is empty), -1 if it failed for
1754+
some reason, or 1 if it was unable to send all the data in the send queue yet
1755+
(this case can only occur if the connection is nonblocking).
17551756
<synopsis>
17561757
int PQflush(PGconn *conn);
17571758
</synopsis>

‎doc/src/sgml/protocol.sgml

Lines changed: 68 additions & 106 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/protocol.sgml,v 1.27 2003/04/16 20:53:38 tgl Exp $ -->
1+
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/protocol.sgml,v 1.28 2003/04/19 00:02:29 tgl Exp $ -->
22

33
<chapter id="protocol">
44
<title>Frontend/Backend Protocol</title>
@@ -819,8 +819,9 @@
819819
Copy-in mode (data transfer to the server) is initiated when the
820820
backend executes a <command>COPY FROM STDIN</> SQL statement. The backend
821821
sends a CopyInResponse message to the frontend. The frontend should
822-
then send zero or more CopyDataRow messages, one per row to be loaded.
823-
(For <command>COPY BINARY</>, send CopyBinaryRow messages instead.)
822+
then send zero or more CopyData messages, forming a stream of input
823+
data. (The message boundaries are not required to have anything to do
824+
with row boundaries, although that is often a reasonable choice.)
824825
The frontend can terminate the copy-in mode by sending either a CopyDone
825826
message (allowing successful termination) or a CopyFail message (which
826827
will cause the <command>COPY</> SQL statement to fail with an
@@ -833,37 +834,33 @@
833834
<para>
834835
In the event of a backend-detected error during copy-in mode (including
835836
receipt of a CopyFail message, or indeed any frontend message other than
836-
CopyDataRow, CopyBinaryRow, or CopyDone), the backend will issue an
837-
ErrorResponse
837+
CopyData or CopyDone), the backend will issue an ErrorResponse
838838
message. If the <command>COPY</> command was issued via an extended-query
839839
message, the backend will now discard frontend messages until a Sync
840840
message is received, then it will issue ReadyForQuery and return to normal
841841
processing. If the <command>COPY</> command was issued in a simple
842842
Query message, the rest of that message is discarded and ReadyForQuery
843-
is issued. In either case, any subsequent CopyDataRow, CopyBinaryRow,
844-
CopyDone, or CopyFail messages issued by the frontend will simply be
845-
dropped.
843+
is issued. In either case, any subsequent CopyData, CopyDone, or CopyFail
844+
messages issued by the frontend will simply be dropped.
846845
</para>
847846

848847
<para>
849848
Copy-out mode (data transfer from the server) is initiated when the
850849
backend executes a <command>COPY TO STDOUT</> SQL statement. The backend
851850
sends a CopyOutResponse message to the frontend, followed by
852-
zero or more CopyDataRow messages, one per row, followed by CopyDone.
853-
(For <command>COPY BINARY</>, CopyBinaryRow messages are sent instead.)
851+
zero or more CopyData messages (always one per row), followed by CopyDone.
854852
The backend then reverts to the command-processing mode it was
855853
in before the <command>COPY</> started, and sends CommandComplete.
856-
The frontend cannot abort
857-
the transfer (short of closing the connection), but it can discard
858-
unwanted CopyDataRow, CopyBinaryRow, and CopyDone messages.
854+
The frontend cannot abort the transfer (short of closing the connection),
855+
but it can discard unwanted CopyData and CopyDone messages.
859856
</para>
860857

861858
<para>
862859
In the event of a backend-detected error during copy-out mode,
863860
the backend will issue an ErrorResponse message and revert to normal
864861
processing. The frontend should treat receipt of ErrorResponse (or
865-
indeed any message type other thanCopyDataRow, CopyBinaryRow, or
866-
CopyDone) as terminatingthe copy-out mode.
862+
indeed any message type other thanCopyData or CopyDone) as terminating
863+
the copy-out mode.
867864
</para>
868865
</sect2>
869866

@@ -1157,7 +1154,9 @@ indicate that it may be sent by a frontend (F), a backend (B), or both
11571154
(F &amp; B).
11581155
Notice that although each message includes a byte count at the beginning,
11591156
the message format is defined so that the message end can be found without
1160-
reference to the byte count. This aids validity checking.
1157+
reference to the byte count. This aids validity checking. (The CopyData
1158+
message is an exception, because it forms part of a data stream; the contents
1159+
may not be interpretable on their own.)
11611160
</para>
11621161

11631162
<VariableList>
@@ -2002,83 +2001,7 @@ CommandComplete (B)
20022001

20032002
<VarListEntry>
20042003
<Term>
2005-
CopyBinaryRow (F &amp; B)
2006-
</Term>
2007-
<ListItem>
2008-
<Para>
2009-
<VariableList>
2010-
<VarListEntry>
2011-
<Term>
2012-
Byte1('b')
2013-
</Term>
2014-
<ListItem>
2015-
<Para>
2016-
Identifies the message as binary COPY data.
2017-
Note that the message body format is identical to the
2018-
<command>COPY BINARY</> file-format representation for
2019-
a single row of data.
2020-
</Para>
2021-
</ListItem>
2022-
</VarListEntry>
2023-
<VarListEntry>
2024-
<Term>
2025-
Int32
2026-
</Term>
2027-
<ListItem>
2028-
<Para>
2029-
Length of message contents in bytes, including self.
2030-
</Para>
2031-
</ListItem>
2032-
</VarListEntry>
2033-
<VarListEntry>
2034-
<Term>
2035-
Int16
2036-
</Term>
2037-
<ListItem>
2038-
<Para>
2039-
Specifies the number of fields in the row (can be zero).
2040-
</Para>
2041-
</ListItem>
2042-
</VarListEntry>
2043-
</VariableList>
2044-
Then, for each field, there is the following:
2045-
<VariableList>
2046-
<VarListEntry>
2047-
<Term>
2048-
Int16
2049-
</Term>
2050-
<ListItem>
2051-
<Para>
2052-
Zero if the field is null, otherwise the <varname>typlen</>
2053-
for the field datatype.
2054-
</Para>
2055-
</ListItem>
2056-
</VarListEntry>
2057-
<VarListEntry>
2058-
<Term>
2059-
Byte<Replaceable>n</Replaceable>
2060-
</Term>
2061-
<ListItem>
2062-
<Para>
2063-
The value of the field itself in binary format.
2064-
Omitted if the field is null.
2065-
<Replaceable>n</Replaceable> is the <varname>typlen</>
2066-
value if <varname>typlen</> is positive. If
2067-
<varname>typlen</> is -1 then the field value begins with
2068-
its own length as an Int32 (the length includes itself).
2069-
</Para>
2070-
</ListItem>
2071-
</VarListEntry>
2072-
</VariableList>
2073-
2074-
</Para>
2075-
</ListItem>
2076-
</VarListEntry>
2077-
2078-
2079-
<VarListEntry>
2080-
<Term>
2081-
CopyDataRow (F &amp; B)
2004+
CopyData (F &amp; B)
20822005
</Term>
20832006
<ListItem>
20842007
<Para>
@@ -2089,7 +2012,7 @@ CopyDataRow (F &amp; B)
20892012
</Term>
20902013
<ListItem>
20912014
<Para>
2092-
Identifies the message astextualCOPY data.
2015+
Identifies the message as COPY data.
20932016
</Para>
20942017
</ListItem>
20952018
</VarListEntry>
@@ -2105,12 +2028,14 @@ CopyDataRow (F &amp; B)
21052028
</VarListEntry>
21062029
<VarListEntry>
21072030
<Term>
2108-
String
2031+
Byte<Replaceable>n</Replaceable>
21092032
</Term>
21102033
<ListItem>
21112034
<Para>
2112-
The textual representation of a single row of table data.
2113-
It should end with a newline.
2035+
Data that forms part of a COPY datastream. Messages sent
2036+
from the backend will always correspond to single data rows,
2037+
but messages sent by frontends may divide the datastream
2038+
arbitrarily.
21142039
</Para>
21152040
</ListItem>
21162041
</VarListEntry>
@@ -2236,8 +2161,7 @@ CopyInResponse (B)
22362161
</Term>
22372162
<ListItem>
22382163
<Para>
2239-
0 for textual copy (CopyDataRow is expected), 1 for
2240-
binary copy (CopyBinaryRow is expected).
2164+
0 for textual copy, 1 for binary copy.
22412165
</Para>
22422166
</ListItem>
22432167
</VarListEntry>
@@ -2283,8 +2207,7 @@ CopyOutResponse (B)
22832207
</Term>
22842208
<ListItem>
22852209
<Para>
2286-
0 for textual copy (CopyDataRow will follow), 1 for
2287-
binary copy (CopyBinaryRow will follow).
2210+
0 for textual copy, 1 for binary copy.
22882211
</Para>
22892212
</ListItem>
22902213
</VarListEntry>
@@ -3606,8 +3529,9 @@ StartupMessage (F)
36063529
<ListItem>
36073530
<Para>
36083531
The protocol version number. The most significant 16 bits are
3609-
the major version number (3 for the format described here).
3610-
The least 16 significant bits are the minor version number.
3532+
the major version number (3 or more for the format described
3533+
here).
3534+
The least significant 16 bits are the minor version number.
36113535
</Para>
36123536
</ListItem>
36133537
</VarListEntry>
@@ -3654,17 +3578,18 @@ StartupMessage (F)
36543578
<ListItem>
36553579
<Para>
36563580
Command-line arguments for the backend. (This is
3657-
deprecated in favor of setting individualGUC
3581+
deprecated in favor of setting individualrun-time
36583582
parameters.)
36593583
</Para>
36603584
</ListItem>
36613585
</VarListEntry>
36623586
</VariableList>
36633587

3664-
In addition to the above, anyGUC parameter that can be
3588+
In addition to the above, anyrun-time parameter that can be
36653589
set at backend start time may be listed. Such settings
36663590
will be applied during backend start (after parsing the
3667-
command-line options if any).
3591+
command-line options if any). The values will act as
3592+
session defaults.
36683593
</Para>
36693594
</ListItem>
36703595
</VarListEntry>
@@ -3913,4 +3838,41 @@ not line breaks.
39133838
</sect1>
39143839

39153840

3841+
<Sect1 id="protocol-changes">
3842+
<Title>Summary of Changes since Protocol 2.0</Title>
3843+
3844+
<para>
3845+
This section provides a quick checklist of changes, for the benefit of
3846+
developers trying to update existing client libraries to protocol 3.0.
3847+
</para>
3848+
3849+
<para>
3850+
The initial startup packet uses a flexible list-of-strings format
3851+
instead of a fixed format. Notice that session default values for run-time
3852+
parameters can now be specified directly in the startup packet. (Actually,
3853+
you could do that before using the <literal>options</> field, but given the
3854+
limited width of <literal>options</> and the lack of any way to quote
3855+
whitespace in the values, it wasn't a very safe technique.)
3856+
</para>
3857+
3858+
<para>
3859+
All messages now have a length count immediately following the message type
3860+
byte (except for startup packets, which have no type byte). Also note that
3861+
PasswordMessage now has a type byte.
3862+
</para>
3863+
3864+
<para>
3865+
COPY data is now encapsulated into CopyData and CopyDone messages. There
3866+
is a well-defined way to recover from errors during COPY.
3867+
</para>
3868+
3869+
<note>
3870+
<para>
3871+
Additional changes will be documented as they are implemented.
3872+
</para>
3873+
</note>
3874+
3875+
</sect1>
3876+
3877+
39163878
</Chapter>

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