[1080042][8f245009b0] Big bundle of regexp engine fixes and improvements

contributed from Tom Lane of the postgres project.

1 files changed, 12 insertions, 8 deletions

diff --git a/generic/regguts.h b/generic/regguts.h
index ac625d5..72bdcb3 100644
--- a/generic/regguts.h
+++ b/generic/regguts.h
@@ -265,8 +265,10 @@ struct arc {
     struct state *from;		/* where it's from (and contained within) */
     struct state *to;		/* where it's to */
     struct arc *outchain;	/* *from's outs chain or free chain */
-#define	freechain	outchain
+    struct arc *outchainRev;	/* back-link in *from's outs chain */
+#define	freechain outchain	/* we do not maintain "freechainRev" */
     struct arc *inchain;	/* *to's ins chain */
+    struct arc *inchainRev;	/* back-link in *to's ins chain */
     struct arc *colorchain;	/* color's arc chain */
     struct arc *colorchainRev;	/* back-link in color's arc chain */
 };
@@ -305,9 +307,6 @@ struct nfa {
     struct colormap *cm;	/* the color map */
     color bos[2];		/* colors, if any, assigned to BOS and BOL */
     color eos[2];		/* colors, if any, assigned to EOS and EOL */
-    size_t size;		/* Current NFA size; differs from nstates as
-				 * it also counts the number of states created
-				 * by children of this state. */
     struct vars *v;		/* simplifies compile error reporting */
     struct nfa *parent;		/* parent NFA, if any */
 };
@@ -337,11 +336,16 @@ struct cnfa {
 #define	NULLCNFA(cnfa)	((cnfa).nstates == 0)
 
 /*
- * Used to limit the maximum NFA size to something sane. [Bug 1810264]
+ * This symbol limits the transient heap space used by the regex compiler,
+ * and thereby also the maximum complexity of NFAs that we'll deal with.
+ * Currently we only count NFA states and arcs against this; the other
+ * transient data is generally not large enough to notice compared to those.
+ * Note that we do not charge anything for the final output data structures
+ * (the compacted NFA and the colormap).
  */
-
-#ifndef REG_MAX_STATES
-#   define REG_MAX_STATES	100000
+#ifndef REG_MAX_COMPILE_SPACE
+#define REG_MAX_COMPILE_SPACE  \
+	(100000 * sizeof(struct state) + 100000 * sizeof(struct arcbatch))
 #endif
 
 /*