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Commit00d9dcf

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pg_dump: Fix gzip compression of empty data
The pg_dump Compressor API has three basic callbacks - Allocate, Writeand End. The gzip implementation (sincee996073) wrongly assumed theWrite function would always be called, and deferred the initializationof the internal compression system until the first such call. But whenthere's no data to compress (e.g. for empty LO), this would result innot finalizing the compression state (because it was not actuallyinitialized), producing invalid dump.Fixed by initializing the internal compression system in the Allocatecall, whenever the caller provides the Write. For decompression thestate is not needed, so we leave the private_data member unpopulated.Introduces a pg_dump TAP test compressing an empty large object.This also rearranges the functions to their original order, to makediffs against older code simpler to understand. Finally, replace anunreachable pg_fatal() with a simple assert check.Reported-by: Justin PryzbyAuthor: Justin Pryzby, Georgios KokolatosReviewed-by: Georgios Kokolatos, Tomas Vondrahttps://postgr.es/m/20230228235834.GC30529%40telsasoft.com
1 parent1671f99 commit00d9dcf

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2 files changed

+100
-59
lines changed

2 files changed

+100
-59
lines changed

‎src/bin/pg_dump/compress_gzip.c

Lines changed: 77 additions & 59 deletions
Original file line numberDiff line numberDiff line change
@@ -33,8 +33,73 @@ typedef struct GzipCompressorState
3333
}GzipCompressorState;
3434

3535
/* Private routines that support gzip compressed data I/O */
36+
staticvoidDeflateCompressorInit(CompressorState*cs);
37+
staticvoidDeflateCompressorEnd(ArchiveHandle*AH,CompressorState*cs);
38+
staticvoidDeflateCompressorCommon(ArchiveHandle*AH,CompressorState*cs,
39+
boolflush);
40+
staticvoidEndCompressorGzip(ArchiveHandle*AH,CompressorState*cs);
41+
staticvoidWriteDataToArchiveGzip(ArchiveHandle*AH,CompressorState*cs,
42+
constvoid*data,size_tdLen);
43+
staticvoidReadDataFromArchiveGzip(ArchiveHandle*AH,CompressorState*cs);
44+
45+
staticvoid
46+
DeflateCompressorInit(CompressorState*cs)
47+
{
48+
GzipCompressorState*gzipcs;
49+
z_streampzp;
50+
51+
gzipcs= (GzipCompressorState*)pg_malloc0(sizeof(GzipCompressorState));
52+
zp=gzipcs->zp= (z_streamp)pg_malloc(sizeof(z_stream));
53+
zp->zalloc=Z_NULL;
54+
zp->zfree=Z_NULL;
55+
zp->opaque=Z_NULL;
56+
57+
/*
58+
* outsize is the buffer size we tell zlib it can output to. We actually
59+
* allocate one extra byte because some routines want to append a trailing
60+
* zero byte to the zlib output.
61+
*/
62+
gzipcs->outsize=DEFAULT_IO_BUFFER_SIZE;
63+
gzipcs->outbuf=pg_malloc(gzipcs->outsize+1);
64+
65+
/* -Z 0 uses the "None" compressor -- not zlib with no compression */
66+
Assert(cs->compression_spec.level!=0);
67+
68+
if (deflateInit(zp,cs->compression_spec.level)!=Z_OK)
69+
pg_fatal("could not initialize compression library: %s",zp->msg);
70+
71+
/* Just be paranoid - maybe End is called after Start, with no Write */
72+
zp->next_out=gzipcs->outbuf;
73+
zp->avail_out=gzipcs->outsize;
74+
75+
/* Keep track of gzipcs */
76+
cs->private_data=gzipcs;
77+
}
78+
79+
staticvoid
80+
DeflateCompressorEnd(ArchiveHandle*AH,CompressorState*cs)
81+
{
82+
GzipCompressorState*gzipcs= (GzipCompressorState*)cs->private_data;
83+
z_streampzp;
84+
85+
zp=gzipcs->zp;
86+
zp->next_in=NULL;
87+
zp->avail_in=0;
88+
89+
/* Flush any remaining data from zlib buffer */
90+
DeflateCompressorCommon(AH,cs, true);
91+
92+
if (deflateEnd(zp)!=Z_OK)
93+
pg_fatal("could not close compression stream: %s",zp->msg);
94+
95+
pg_free(gzipcs->outbuf);
96+
pg_free(gzipcs->zp);
97+
pg_free(gzipcs);
98+
cs->private_data=NULL;
99+
}
100+
36101
staticvoid
37-
DeflateCompressorGzip(ArchiveHandle*AH,CompressorState*cs,boolflush)
102+
DeflateCompressorCommon(ArchiveHandle*AH,CompressorState*cs,boolflush)
38103
{
39104
GzipCompressorState*gzipcs= (GzipCompressorState*)cs->private_data;
40105
z_streampzp=gzipcs->zp;
@@ -78,69 +143,20 @@ DeflateCompressorGzip(ArchiveHandle *AH, CompressorState *cs, bool flush)
78143
staticvoid
79144
EndCompressorGzip(ArchiveHandle*AH,CompressorState*cs)
80145
{
81-
GzipCompressorState*gzipcs= (GzipCompressorState*)cs->private_data;
82-
z_streampzp;
83-
84-
if (gzipcs->zp)
85-
{
86-
zp=gzipcs->zp;
87-
zp->next_in=NULL;
88-
zp->avail_in=0;
89-
90-
/* Flush any remaining data from zlib buffer */
91-
DeflateCompressorGzip(AH,cs, true);
92-
93-
if (deflateEnd(zp)!=Z_OK)
94-
pg_fatal("could not close compression stream: %s",zp->msg);
95-
96-
pg_free(gzipcs->outbuf);
97-
pg_free(gzipcs->zp);
98-
}
99-
100-
pg_free(gzipcs);
101-
cs->private_data=NULL;
146+
/* If deflation was initialized, finalize it */
147+
if (cs->private_data)
148+
DeflateCompressorEnd(AH,cs);
102149
}
103150

104151
staticvoid
105152
WriteDataToArchiveGzip(ArchiveHandle*AH,CompressorState*cs,
106153
constvoid*data,size_tdLen)
107154
{
108155
GzipCompressorState*gzipcs= (GzipCompressorState*)cs->private_data;
109-
z_streampzp;
110-
111-
if (!gzipcs->zp)
112-
{
113-
zp=gzipcs->zp= (z_streamp)pg_malloc(sizeof(z_stream));
114-
zp->zalloc=Z_NULL;
115-
zp->zfree=Z_NULL;
116-
zp->opaque=Z_NULL;
117-
118-
/*
119-
* outsize is the buffer size we tell zlib it can output to. We
120-
* actually allocate one extra byte because some routines want to
121-
* append a trailing zero byte to the zlib output.
122-
*/
123-
gzipcs->outsize=DEFAULT_IO_BUFFER_SIZE;
124-
gzipcs->outbuf=pg_malloc(gzipcs->outsize+1);
125-
126-
/*
127-
* A level of zero simply copies the input one block at the time. This
128-
* is probably not what the user wanted when calling this interface.
129-
*/
130-
if (cs->compression_spec.level==0)
131-
pg_fatal("requested to compress the archive yet no level was specified");
132-
133-
if (deflateInit(zp,cs->compression_spec.level)!=Z_OK)
134-
pg_fatal("could not initialize compression library: %s",zp->msg);
135-
136-
/* Just be paranoid - maybe End is called after Start, with no Write */
137-
zp->next_out=gzipcs->outbuf;
138-
zp->avail_out=gzipcs->outsize;
139-
}
140156

141157
gzipcs->zp->next_in= (void*)unconstify(void*,data);
142158
gzipcs->zp->avail_in=dLen;
143-
DeflateCompressorGzip(AH,cs, false);
159+
DeflateCompressorCommon(AH,cs, false);
144160
}
145161

146162
staticvoid
@@ -214,17 +230,19 @@ void
214230
InitCompressorGzip(CompressorState*cs,
215231
constpg_compress_specificationcompression_spec)
216232
{
217-
GzipCompressorState*gzipcs;
218-
219233
cs->readData=ReadDataFromArchiveGzip;
220234
cs->writeData=WriteDataToArchiveGzip;
221235
cs->end=EndCompressorGzip;
222236

223237
cs->compression_spec=compression_spec;
224238

225-
gzipcs= (GzipCompressorState*)pg_malloc0(sizeof(GzipCompressorState));
226-
227-
cs->private_data=gzipcs;
239+
/*
240+
* If the caller has defined a write function, prepare the necessary
241+
* state. Note that if the data is empty, End may be called immediately
242+
* after Init, without ever calling Write.
243+
*/
244+
if (cs->writeF)
245+
DeflateCompressorInit(cs);
228246
}
229247

230248

‎src/bin/pg_dump/t/002_pg_dump.pl

Lines changed: 23 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1265,6 +1265,29 @@
12651265
},
12661266
},
12671267

1268+
'LO create (with no data)'=> {
1269+
create_sql=>
1270+
'SELECT pg_catalog.lo_create(0);',
1271+
regexp=>qr/^
1272+
\QSELECT pg_catalog.lo_open\E\('\d+',\ \d+\);\n
1273+
\QSELECT pg_catalog.lo_close(0);\E
1274+
/xm,
1275+
like=> {
1276+
%full_runs,
1277+
column_inserts=> 1,
1278+
data_only=> 1,
1279+
inserts=> 1,
1280+
section_data=> 1,
1281+
test_schema_plus_large_objects=> 1,
1282+
},
1283+
unlike=> {
1284+
binary_upgrade=> 1,
1285+
no_large_objects=> 1,
1286+
schema_only=> 1,
1287+
section_pre_data=> 1,
1288+
},
1289+
},
1290+
12681291
'COMMENT ON DATABASE postgres'=> {
12691292
regexp=>qr/^COMMENT ON DATABASE postgres IS .+;/m,
12701293

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