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Add a debugging option to stress-test outfuncs.c and readfuncs.c.

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In the normal course of operation, query trees will be serialized only if
they are stored as views or rules; and plan trees will be serialized only
if they get passed to parallel-query workers.  This leaves an awful lot of
opportunity for bugs/oversights to not get detected, as indeed we've just
been reminded of the hard way.

To improve matters, this patch adds a new compile option
WRITE_READ_PARSE_PLAN_TREES, which is modeled on the longstanding option
COPY_PARSE_PLAN_TREES; but instead of passing all parse and plan trees
through copyObject, it passes them through nodeToString + stringToNode.
Enabling this option in a buildfarm animal or two will catch problems
at least for cases that are exercised by the regression tests.

A small problem with this idea is that readfuncs.c historically has
discarded location fields, on the reasonable grounds that parse
locations in a retrieved view are not relevant to the current query.
But doing that in WRITE_READ_PARSE_PLAN_TREES breaks pg_stat_statements,
and it could cause problems for future improvements that might try to
report error locations at runtime.  To fix that, provide a variant
behavior in readfuncs.c that makes it restore location fields when
told to.

In passing, const-ify the string arguments of stringToNode and its
subsidiary functions, just because it annoyed me that they weren't
const already.

Discussion: https://postgr.es/m/17114.1537138992@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2018-09-18 17:11:54 -04:00
parent db1071d4ee
commit d0cfc3d6a4
7 changed files with 170 additions and 29 deletions
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31
src/backend/nodes/readfuncs.c
View File

@ -17,10 +17,14 @@
* never read executor state trees, either.
*
* Parse location fields are written out by outfuncs.c, but only for
* possible debugging use. When reading a location field, we discard
* debugging use. When reading a location field, we normally discard
* the stored value and set the location field to -1 (ie, "unknown").
* This is because nodes coming from a stored rule should not be thought
* to have a known location in the current query's text.
* However, if restore_location_fields is true, we do restore location
* fields from the string. This is currently intended only for use by the
* WRITE_READ_PARSE_PLAN_TREES test code, which doesn't want to cause
* any change in the node contents.
*
*-------------------------------------------------------------------------
*/
@ -51,7 +55,7 @@
/* And a few guys need only the pg_strtok support fields */
#define READ_TEMP_LOCALS() \
char *token; \
const char *token; \
int length
/* ... but most need both */
@ -120,12 +124,19 @@
token = pg_strtok(&length); /* get field value */ \
local_node->fldname = nullable_string(token, length)
/* Read a parse location field (and throw away the value, per notes above) */
/* Read a parse location field (and possibly throw away the value) */
#ifdef WRITE_READ_PARSE_PLAN_TREES
#define READ_LOCATION_FIELD(fldname) \
token = pg_strtok(&length); /* skip :fldname */ \
token = pg_strtok(&length); /* get field value */ \
local_node->fldname = restore_location_fields ? atoi(token) : -1
#else
#define READ_LOCATION_FIELD(fldname) \
token = pg_strtok(&length); /* skip :fldname */ \
token = pg_strtok(&length); /* get field value */ \
(void) token; /* in case not used elsewhere */ \
local_node->fldname = -1 /* set field to "unknown" */
#endif
/* Read a Node field */
#define READ_NODE_FIELD(fldname) \
@ -2804,7 +2815,7 @@ readDatum(bool typbyval)
Size length,
i;
int tokenLength;
char *token;
const char *token;
Datum res;
char *s;
@ -2817,7 +2828,7 @@ readDatum(bool typbyval)
token = pg_strtok(&tokenLength); /* read the '[' */
if (token == NULL || token[0] != '[')
elog(ERROR, "expected \"[\" to start datum, but got \"%s\"; length = %zu",
token ? (const char *) token : "[NULL]", length);
token ? token : "[NULL]", length);
if (typbyval)
{
@ -2847,7 +2858,7 @@ readDatum(bool typbyval)
token = pg_strtok(&tokenLength); /* read the ']' */
if (token == NULL || token[0] != ']')
elog(ERROR, "expected \"]\" to end datum, but got \"%s\"; length = %zu",
token ? (const char *) token : "[NULL]", length);
token ? token : "[NULL]", length);
return res;
}
@ -2860,7 +2871,7 @@ readAttrNumberCols(int numCols)
{
int tokenLength,
i;
char *token;
const char *token;
AttrNumber *attr_vals;
if (numCols <= 0)
@ -2884,7 +2895,7 @@ readOidCols(int numCols)
{
int tokenLength,
i;
char *token;
const char *token;
Oid *oid_vals;
if (numCols <= 0)
@ -2908,7 +2919,7 @@ readIntCols(int numCols)
{
int tokenLength,
i;
char *token;
const char *token;
int *int_vals;
if (numCols <= 0)
@ -2932,7 +2943,7 @@ readBoolCols(int numCols)
{
int tokenLength,
i;
char *token;
const char *token;
bool *bool_vals;
if (numCols <= 0)