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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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13
src/include/nodes/readfuncs.h
View File

@@ -16,12 +16,19 @@
#include "nodes/nodes.h"
/*
* variable in read.c that needs to be accessible to readfuncs.c
*/
#ifdef WRITE_READ_PARSE_PLAN_TREES
extern bool restore_location_fields;
#endif
/*
* prototypes for functions in read.c (the lisp token parser)
*/
extern char *pg_strtok(int *length);
extern char *debackslash(char *token, int length);
extern void *nodeRead(char *token, int tok_len);
extern const char *pg_strtok(int *length);
extern char *debackslash(const char *token, int length);
extern void *nodeRead(const char *token, int tok_len);
/*
* prototypes for functions in readfuncs.c